关于String()?

[zyq_123]

String()这个函数的原委是怎样的？

[gloom]

Windwos 下程序的开头也就是入口是在WinMain中。就是你上面贴的那个了。

[Jagen在路上]

basic_string

Summary

A templatized class for handling sequences of character-like entities. string and wstring are specialized versions of basic_string for char's and wchar_t's, respectively.

typedef basic_string <char> string;
typedef basic_string <wchar_t> wstring;

Synopsis

#include <string>
template <class charT,
class traits = char_traits<charT>,
class Allocator = allocator<charT> >
class basic_string;

Description

basic_string<charT, traits, Allocator> is a homogeneous collection of character-like entities that includes string functions such as compare, append, assign, insert, remove, and replace, along with various searches. basic_string also functions as an STL sequence container that provides random access iterators. This allows some of the generic algorithms to apply to strings.

Any underlying character-like type may be used as long as an appropriate char_traits class is included or the default traits class is applicable.

Interface

template <class charT,
class traits = char_traits<charT>,
class Allocator = allocator<charT> >
class basic_string {
public:
// Types
typedef traits traits_type;
typedef typename traits::char_type value_type;
typedef Allocator allocator_type;
typedef typename Allocator::size_type size_type;
typedef typename Allocator::difference_type difference_type;
typedef typename Allocator::reference reference;

typedef typename Allocator::const_reference const_reference;
typedef typename Allocator::pointer pointer;
typedef typename Allocator::const_pointer const_pointer;
typedef typename Allocator::pointer iterator;
typedef typename Allocator::const_pointer const_iterator;
typedef std::reverse_iterator<const_iterator>
const_reverse_iterator;
typedef std::reverse_iterator<iterator> reverse_iterator;
static const size_type npos = -1;

// Constructors/Destructors
explicit basic_string(const Allocator& = Allocator());
basic_string (const basic_string<charT, traits,
Allocator>&);
basic_string(const basic_string&, size_type,
size_type = npos,
const Allocator& a = Allocator());
basic_string(const charT*, size_type,
const Allocator& = Allocator());
basic_string(const charT*, const Allocator& = Allocator());
basic_string(size_type, charT,
const Allocator& = Allocator());

template <class InputIterator>
basic_string(InputIterator, InputIterator,
const Allocator& = Allocator());
~basic_string();
// Assignment operators
basic_string& operator=(const basic_string&);
basic_string& operator=(const charT*);
basic_string& operator=(charT);
// Iterators
iterator begin();
const_iterator begin() const;
iterator end();
const_iterator end() const;
reverse_iterator rbegin();
const_reverse_iterator rbegin() const;

reverse_iterator rend();
const_reverse_iterator rend() const;
// Capacity
size_type size() const;
size_type length() const;
size_type max_size() const;
void resize(size_type, charT);
void resize(size_type);
size_type capacity() const;
void reserve(size_type = 0);
bool empty() const;
// Element access
const_reference operator[](size_type) const;
reference operator[](size_type);

const_reference at(size_type) const;
reference at(size_type);
// Modifiers
basic_string& operator+=(const basic_string&);
basic_string& operator+=(const charT*);
basic_string& operator+=(charT);

basic_string& append(const basic_string&);
basic_string& append(const basic_string&,
size_type, size_type);
basic_string& append(const charT*, size_type);
basic_string& append(const charT*);
basic_string& append(size_type, charT);

template<class InputIterator>
basic_string& append(InputIterator, InputIterator);

basic_string& assign(const basic_string&);
basic_string& assign(const basic_string&,
size_type, size_type);
basic_string& assign(const charT*, size_type);
basic_string& assign(const charT*);
basic_string& assign(size_type, charT);
template<class InputIterator>
basic_string& assign(InputIterator, InputIterator);

basic_string& insert(size_type, const basic_string&);

basic_string& insert(size_type, const basic_string&,
size_type, size_type);
basic_string& insert(size_type, const charT*, size_type);
basic_string& insert(size_type, const charT*);
basic_string& insert(size_type, size_type, charT);
iterator insert(iterator, charT = charT());
void insert(iterator, size_type, charT);
template<class InputIterator>
void insert(iterator, InputIterator, InputIterator);
basic_string& erase(size_type = 0, size_type= npos);

iterator erase(iterator);
iterator erase(iterator, iterator);
basic_string& replace(size_type, size_type,
const basic_string&);
basic_string& replace(size_type, size_type,
const basic_string&,
size_type, size_type);
basic_string& replace(size_type, size_type,
const charT*, size_type);
basic_string& replace(size_type, size_type,
const charT*);

basic_string& replace(size_type, size_type,
size_type, charT);
basic_string& replace(iterator, iterator,
const basic_string&);
basic_string& replace(iterator, iterator,
const charT*, size_type);
basic_string& replace(iterator, iterator,
const charT*);
basic_string& replace(iterator, iterator,
size_type, charT);
template<class InputIterator>

basic_string& replace(iterator, iterator,
InputIterator, InputIterator);
size_type copy(charT*, size_type, size_type = 0) const;
void swap(basic_string<charT, traits, Allocator>&);
// String operations
const charT* c_str() const;
const charT* data() const;
const allocator_type& get_allocator() const;

size_type find(const basic_string&,
size_type = 0) const;
size_type find(const charT*,
size_type, size_type) const;

size_type find(const charT*, size_type = 0) const;
size_type find(charT, size_type = 0) const;
size_type rfind(const basic_string&,
size_type = npos) const;
size_type rfind(const charT*,
size_type, size_type) const;
size_type rfind(const charT*,
size_type = npos) const;
size_type rfind(charT, size_type = npos) const;
size_type find_first_of(const basic_string&,
size_type = 0) const;

size_type find_first_of(const charT*,
size_type, size_type) const;
size_type find_first_of(const charT*,
size_type = 0) const;
size_type find_first_of(charT, size_type = 0) const;
size_type find_last_of(const basic_string&,
size_type = npos) const;
size_type find_last_of(const charT*,
size_type, size_type) const;
size_type find_last_of(const charT*, size_type = npos)

const;
size_type find_last_of(charT, size_type = npos) const;
size_type find_first_not_of(const basic_string&,
size_type = 0) const;
size_type find_first_not_of(const charT*,
size_type, size_type) const;
size_type find_first_not_of(const charT*, size_type = 0)
const;
size_type find_first_not_of(charT, size_type = 0) const;
size_type find_last_not_of(const basic_string&,

size_type = npos) const;
size_type find_last_not_of(const charT*,
size_type, size_type) const;
size_type find_last_not_of(const charT*,
size_type = npos) const;
size_type find_last_not_of(charT, size_type = npos)
const;
basic_string substr(size_type = 0, size_type = npos)
const;
int compare(const basic_string&) const;

int compare(size_type, size_type, const basic_string&)
const;
int compare(size_type, size_type, const basic_string&,
size_type, size_type) const;
int compare(size_type, size_type, charT*) const;
int compare(charT*) const;
int compare(size_type, size_type, const charT*,
size_type) const;
};
// Non-member Operators
template <class charT, class traits, class Allocator>
basic_string operator+ (const basic_string&,

const basic_string&);
template <class charT, class traits, class Allocator>
basic_string operator+ (const charT*, const basic_string&);
template <class charT, class traits, class Allocator>
basic_string operator+ (charT, const basic_string&);
template <class charT, class traits, class Allocator>
basic_string operator+ (const basic_string&, const charT*);
template <class charT, class traits, class Allocator>
basic_string operator+ (const basic_string&, charT);

template <class charT, class traits, class Allocator>
bool operator== (const basic_string&, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator== (const charT*, const basic_string&);
template <class charT, class traits , class Allocator>
bool operator== (const basic_string&, const charT*);
template <class charT, class traits, class Allocator>
bool operator< (const basic_string&, const basic_string&);
template <class charT, class traits, class Allocator>

bool operator< (const charT*, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator< (const basic_string&, const charT*);
template <class charT, class traits, class Allocator>
bool operator!= (const basic_string&, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator!= (const charT*, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator!= (const basic_string&, const charT*);

template <class charT, class traits, class Allocator>
bool operator> (const basic_string&, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator> (const charT*, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator> (const basic_string&, const charT*);
template <class charT, class traits, class Allocator>
bool operator<= (const basic_string&, const basic_string&);
template <class charT, class traits, class Allocator>

bool operator<= (const charT*, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator<= (const basic_string&, const charT*);

template <class charT, class traits, class Allocator>
bool operator>= (const basic_string&, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator>= (const charT*, const basic_string&);
template <class charT, class traits, class Allocator>
bool operator>= (const basic_string&, const charT*);

template <class charT, class traits, class Allocator>
void swap(basic_string<charT,traits,Allocator>& a,
basic_string<charT,traits,Allocator>& b);
template<class charT, class traits, class Allocator>
basic_istream<charT, traits>& operator>>
(istream&, basic_string&);
template <class charT, class traits, class Allocator>
basic_ostream<charT, traits>& operator<<
(ostream&, const basic_string&);
template <class Stream, class charT,

class traits, class Allocator>
basic_istream<charT, traits>& getline
(Stream&, basic_string&, charT);

Constructors

In all cases, the Allocator parameter is used for storage management.

explicit
basic_string (const Allocator& a = Allocator());

The default constructor. Creates a basic_string with the following effects:

data() a non-null pointer that is copyable and can have 0 added to it
size() 0
capacity() an unspecified value

basic_string (const basic_string<T, traits,
Allocator>& str);

Creates a string that is a copy of str.

basic_string (const basic_string& str, size_type pos,
size_type n= npos, const allocator&
a=allocator());

Creates a string of pos<=size() and determines length rlen of the initial string value as the smaller of n and str.size() - pos. This has the following effects:

data() points to the first element of an allocated copy of rlen elements of the string controlled by str beginning at position pos
size() rlen
capacity() a value at least as large as size()
get_allocator() str.get_allocator()

An out_of_range exception is thrown if pos>str.size().

basic_string (const charT* s, size_type n,
const Allocator& a = Allocator());

Creates a string that contains the first n characters of s. s must not be a NULL pointer. The effects of this constructor are:

data() points to the first element of an allocated copy of the array whose first element is pointed to by s
size() n
capacity() a value at least as large as size()

A length_error exception is thrown if n == npos.

basic_string (const charT * s,
const Allocator& a = Allocator());

Constructs a string containing all characters in s up to, but not including, a traits::eos() character. s must not be a null pointer. The effects of this constructor are:

data() points to the first element of an allocated copy of the array whose first element is pointed to by s
size() traits::length(s)
capacity() a value at least as large as size()

basic_string (size_type n, charT c,
const Allocator& a = Allocator());

Constructs a string containing n repetitions of c. A length_error exception is thrown if n == npos. The effects of this constructor are:

data() points to the first element of an allocated array of n elements, each storing the initial value c
size() n
capacity() a value at least as large as size()

template <class InputIterator>
basic_string (InputIterator first, InputIterator last,
const Allocator& a = Allocator());

Creates a basic_string of length last - first filled with all values obtained by dereferencing the InputIterators on the range [first, last). The effects of this constructor are:

data() points to the first element of an allocated copy of the elements in the range [first,last)
size() distance between first and last
capacity() a value at least as large as size()

Destructors

~basic_string ();

Releases any allocated memory for this basic_string.

Operators

basic_string&
operator= (const basic_string& str);

Sets the contents of this string to be the same as str. The effects of operator= are:

data() points to the first element of an allocated copy of the array whose first element is pointed to by str.size()
size() str.size()
capacity() a value at least as large as size()

basic_string&
operator= (const charT * s);

Sets the contents of this string to be the same as s up to, but not including, the traits::eos() character.

basic_string&
operator= (charT c);

Sets the contents of this string to be equal to the single charT c.

const_reference
operator[] (size_type pos) const;
reference
operator[] (size_type pos);

If pos < size(), returns the element at position pos in this string. If pos == size(), the const version returns charT(), the behavior of the non-const version is undefined. The reference returned by either version is invalidated by any call to c_str(), data(), or any non-const member function for the object.

basic_string&
operator+= (const basic_string& s);
basic_string&
operator+= (const charT* s);
basic_string&
operator+= (charT c);

Concatenates a string onto the current contents of this string. The second member operator uses traits::length() to determine the number of elements from s to add. The third member operator adds the single character c. All return a reference to this string after completion.

Iterators

iterator begin ();
const_iterator begin () const;

Returns an iterator initialized to the first element of the string.

iterator end ();
const_iterator end () const;

Returns an iterator initialized to the position after the last element of the string.

reverse_iterator rbegin ();
const_reverse_iterator rbegin () const;

Returns an iterator equivalent to reverse_iterator(end()).

reverse_iterator rend ();
const_reverse_iterator rend () const;

Returns an iterator equivalent to reverse_iterator(begin()).

Allocator

const allocator_type get_allocator () const;

Returns a copy of the allocator used by self for storage management.

Member Functions

basic_string&
append (const basic_string& s, size_type pos,
size_type npos);
basic_string&
append (const basic_string& s);
basic_string&
append (const charT* s, size_type n);
basic_string&
append (const charT* s);
basic_string&
append (size_type n, charT c );
template<class InputIterator>
basic_string&
append (InputIterator first, InputIterator last);

Append another string to the end of this string. The first two functions append the lesser of n and s.size() - pos characters of s, beginning at position pos to this string. The second member throws an out_of_range exception if pos > str.size(). The third member appends n characters of the array pointed to by s. The fourth variation appends elements from the array pointed to by s up to, but not including, a charT() character. The fifth variation appends n repetitions of c. The final append function appends the elements specified in the range [first, last).

All functions throw a length_error exception if the resulting lengths exceed max_size(). All return a reference to this string after completion.

basic_string&
assign (const basic_string& s);
basic_string&
assign (const basic_string& s,
size_type pos, size_type n);
basic_string&
assign (const charT* s, size_type n);
basic_string&
assign (const charT* s);
basic_string&
assign (size_type n, charT c );
template<class InputIterator>
basic_string&
assign (InputIterator first, InputIterator last);

Replace the value of this string with the value of another.

All versions of the function assign values to this string. The first two variations assign the lesser of n and s.size() - pos characters of s, beginning at position pos. The second variation throws an out_of_range exception if pos > str.size(). The third version of the function assigns n characters of the array pointed to by s. The fourth version assigns elements from the array pointed to by s up to, but not including, a charT() character. The fifth assigns one or n repetitions of c. The last variation assigns the members specified by the range [first, last).

All functions throw a length_error exception if the resulting lengths exceed max_size(). All return a reference to this string after completion.

const_reference
at (size_type pos) const;
reference
at (size_type pos);

If pos < size(), returns the element at position pos in this string. Otherwise, an out_of_range exception is thrown.

size_type
capacity () const;

Returns the current storage capacity of the string. This is guaranteed to be at least as large as size().

int
compare (const basic_string& str);

Returns the result of a lexicographical comparison between elements of this string and elements of str. The return value is:

<0 if size() < str.size()
0 if size() == str.size()
>0 if size() > str.size()

int
compare (size_type pos1, size_type n1,
const basic_string& str) const;
int
compare (size_type pos1, size_type n1,
const basic_string& str,
size_type pos2, size_type n2) const;
int
compare (charT* s) const;
int
compare (size_type pos, size_type n1, charT* s) const;
int
compare (size_type pos, size_type n1, charT* s,
size_type n2) const;

Returns the result of a lexicographical comparison between elements of this string and a given comparison string. The members return, respectively:

basic_string(*this,pos1,n1).compare (str)
basic_string(*this,pos1,n1).compare (basic_string
(str, pos2, n2))
*this.compare (basic_string(s))
basic_string(*this,pos,n1).compare (basic_string
(s, npos))
basic_string(*this,pos,n1).compare (basic_string (s,n2))
size_type
copy (charT* s, size_type n, size_type pos = 0) const;

Replaces elements in memory with copies of elements from this string. An out_of_range exception is thrown if pos > size(). The lesser of n and size() - pos elements of this string, starting at position pos, are copied into the array pointed to by s. No terminating null is appended to s.

const charT*
c_str () const;
const charT*
data () const;

Returns a pointer to the initial element of an array whose first size() elements are copies of the elements in this string. A charT() element is appended to the end. The elements of the array may not be altered, and the returned pointer is only valid until a non-const member function of this string is called. If size() is zero, the data() function returns a non-NULL pointer.

bool empty () const;

Returns size() == 0.

basic_string&
erase (size_type pos = 0, size_type n = npos);
iterator
erase (iterator p);
iterator
erase (iterator first, iterator last);

This function removes elements from the string, collapsing the remaining elements, as necessary, to remove any space left empty.

The first version of the function removes the smaller of n and size() - pos starting at position pos. An out_of_range exception is thrown if pos > size().

For the second version, p must be a valid iterator on the string, and the function removes the character referred to by p.

For the last version of erase, both first and last must be valid iterators on the string, and the function removes the characters defined by the range [first, last). The destructors for all removed characters are called.

All versions of erase return a reference to the string after completion.

size_type
find (const basic_string& str, size_type pos = 0) const;

Searches for the first occurrence of the substring specified by str in this string, starting at position pos. If found, it returns the index of the first character of the matching substring. If not found, returns npos. Equality is defined by traits::eq().

size_type
find (const charT* s, size_type pos, size_type n) const;
size_type
find (const charT* s, size_type pos = 0) const;
size_type
find (charT c, size_type pos = 0) const;

Searches for the first sequence of characters in this string that match a specified string. The variations of this function return, respectively:

find(basic_string(s,n), pos)
find(basic_string(s), pos)
find(basic_string(1, c), pos)
size_type
find_first_not_of (const basic_string& str,
size_type pos = 0) const;

Searches for the first element of this string at or after position pos that is not equal to any element of str. If found, find_first_not_of returns the index of the non-matching character. If all of the characters match, the function returns npos. Equality is defined by traits::eq().

size_type
find_first_not_of (const charT* s,
size_type pos, size_type n) const;
size_type
find_first_not_of (const charT* s,
size_type pos = 0) const;
size_type
find_first_not_of (charT c, size_type pos = 0) const;

Searches for the first element in this string at or after position pos that is not equal to any element of a given set of characters. The members return, respectively:

find_first_not_of(basic_string(s,n), pos)
find_first_not_of(basic_string(s), pos)
find_first_not_of(basic_string(1, c), pos)
size_type
find_first_of(const basic_string& str,
size_type pos = 0) const;

Searches for the first occurrence at or after position pos of any element of str in this string. If found, the index of this matching character is returned. If not found, npos is returned. Equality is defined by traits::eq().

size_type
find_first_of(const charT* s, size_type pos,
size_type n) const;
size_type
find_first_of(const charT* s, size_type pos = 0) const;
size_type
find_first_of (charT c, size_type pos = 0) const;

Searches for the first occurrence in this string of any element in a specified string. The find_first_of variations return, respectively:

find_first_of(basic_string(s,n), pos)
find_first_of(basic_string(s), pos)
find_first_of(basic_string(1, c), pos)
size_type
find_last_not_of(const basic_string& str,
size_type pos = npos) const;

Searches for the last element of this string at or before position pos that is not equal to any element of str. If find_last_not_of finds a non-matching element, it returns the index of the character. If all the elements match, the function returns npos. Equality is defined by traits::eq().

size_type
find_last_not_of(const charT* s,
size_type pos, size_type n) const;
size_type
find_last_not_of(const charT* s, size_type pos = npos) const;
size_type
find_last_not_of(charT c, size_type pos = npos) const;

Searches for the last element in this string at or before position pos that is not equal to any element of a given set of characters. The members return, respectively:

find_last_not_of(basic_string(s,n), pos)
find_last_not_of(basic_string(s), pos)
find_last_not_of(basic_string(1, c), pos)
size_type
find_last_of(const basic_string& str,
size_type pos = npos) const;

Searches for the last occurrence of any element of str at or before position pos in this string. If found, find_last_of returns the index of the matching character. If not found, find_last_of returns npos. Equality is defined by traits::eq().

size_type
find_last_of(const charT* s, size_type pos,
size_type n) const;
size_type
find_last_of(const charT* s, size_type pos = npos) const;
size_type
find_last_of(charT c, size_type pos = npos) const;

Searches for the last occurrence in this string of any element in a specified string. The members return, respectively:

find_last_of(basic_string(s,n), pos)
find_last_of(basic_string(s), pos)
find_last_of(basic_string(1, c), pos)
basic_string&
insert(size_type pos1, const basic_string& s);
basic_string&
insert(size_type pos, const basic_string& s,
size_type pos2 = 0, size_type n = npos);
basic_string&
insert(size_type pos, const charT* s, size_type n);
basic_string&
insert(size_type pos, const charT* s);
basic_string&
insert(size_type pos, size_type n, charT c);

Inserts additional elements at position pos in this string. All of the variants of this function throw an out_of_range exception if pos > size(). All variants also throw a length_error if the resulting strings exceed max_size(). Elements of this string are moved apart as necessary to accommodate the inserted elements. All return a reference to this string after completion.

The second variation of this function inserts the lesser of n and s.size() - pos2 characters of s, beginning at position pos2 in this string. This version throws an out_of_range exception if pos2 > s.size().

The third version inserts n characters of the array pointed to by s.

The fourth inserts elements from the array pointed to by s up to, but not including, a charT() character.

Finally, the fifth variation inserts n repetitions of c.

iterator
insert(iterator p, charT);
void
insert(iterator p, size_type n, charT c);
template<class InputIterator>
void
insert(iterator p, InputIterator first, InputIterator last);

Inserts additional elements in this string immediately before the character referred to by p. All of these versions of insert require that p is a valid iterator on this string. The first version inserts a copy of c. The second version inserts n repetitions of c. The third version inserts characters in the range [first, last). The first version returns p.

size_type
length() const;

Returns the number of elements contained in this string.

size_type
max_size() const;

Returns the maximum possible size of the string.

size_type
rfind (const basic_string& str, size_type pos = npos) const;

Searches for the last occurrence of the substring specified by str in the string, where the index of the first character of the substring is less than pos. If found, the index of the first character that matches substring is returned. If not found, npos is returned. Equality is defined by traits::eq().

size_type
rfind(const charT* s, size_type pos, size_type n) const;
size_type
rfind(const charT* s, size_type pos = npos) const;
size_type
rfind(charT c, size_type pos = npos) const;

Searches for the last sequence of characters in this string matching a specified string. The rfind variations return, respectively:

rfind(basic_string(s,n), pos)
rfind(basic_string(s), pos)
rfind(basic_string(1, c), pos)
basic_string&
replace(size_type pos, size_type n1, const basic_string& s);
basic_string&
replace(size_type pos1, size_type n1,
const basic_string& str,
size_type pos2, size_type n2);
basic_string&
replace(size_type pos, size_type n1, const charT* s,
size_type n2);
basic_string&
replace(size_type pos, size_type n1, const charT* s);

basic_string&
replace(size_type pos, size_type n1, size_type n2, charT c);

The replace function replaces selected elements of this string with an alternate set of elements. All of these versions insert the new elements in place of n1 elements in this string, starting at position pos. They each throw an out_of_range exception if pos1 > size() and a length_error exception if the resulting string size exceeds max_size().

The second version replaces elements of the original string with n2 characters from string s starting at position pos2. It throws the out_of_range exception if pos2 > s.size(). The third variation of the function replaces elements in the original string with n2 elements from the array pointed to by s. The fourth version replaces elements in the string with elements from the array pointed to by s, up to, but not including, a charT() character. The fifth replaces n elements with n2 repetitions of character c.

basic_string&
replace(iterator i1, iterator i2,
const basic_string& str);
basic_string&
replace(iterator i1, iterator i2, const charT* s,
size_type n);
basic_string&
replace(iterator i1, iterator i2, const charT* s);
basic_string&
replace(iterator i1, iterator i2, size_type n,
charT c);
template<class InputIterator>
basic_string&
replace(iterator i1, iterator i2,
InputIterator j1, InputIterator j2);

Replaces selected elements of this string with an alternative set of elements. All of these versions of replace require iterators i1 and i2 to be valid iterators on this string. The elements specified by the range [i1, i2) are replaced by the new elements.

The first version shown here replaces all members in str.

The second version starts at position i1, and replaces the next n characters with n characters of the array pointed to by s.

The third variation replaces string elements with elements from the array pointed to by s up to, but not including, a charT() character.

The fourth version replaces string elements with n repetitions of c.

The last variation shown here replaces string elements with the members specified in the range [j1, j2).

void
reserve(size_type res_arg=0);

Assures that the storage capacity is at least res_arg. Throws a length_error exception if res_arg > max_size().

void
resize(size_type n, charT c);
void
resize(size_type n);

Changes the capacity of this string to n. If the new capacity is smaller than the current size of the string, then the string is truncated. If the capacity is larger, then the string is padded with c characters. The latter resize member pads the string with default characters specified by charT(). Throws a length_error exception if n > max_size().

size type
size() const;

Return the number of elements contained in this string.

basic_string
substr(size_type pos = 0, size_type n = npos) const;

Returns a string composed of copies of the lesser of n and size() characters in this string starting at index pos. Throws an out_of_range exception if pos > size().

void
swap(basic_string& s);

Swaps the contents of this string with the contents of s.

Non-member Operators

template<class charT, class traits, class Allocator>
basic_string
operator+(const basic_string& lhs, const basic_string& rhs);

Returns a string of length lhs.size() + rhs.size(), where the first lhs.size() elements are copies of the elements of lhs, and the next rhs.size() elements are copies of the elements of rhs.

template<class charT, class traits, class Allocator>
basic_string
operator+(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
basic_string
operator+(charT lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
basic_string
operator+(const basic_string& lhs, const charT* rhs);
template<class charT, class traits, class Allocator>
basic_string
operator+(const basic_string& lhs, charT rhs);

Returns a string that represents the concatenation of two string-like entities. These functions return, respectively:

basic_string(lhs) + rhs
basic_string(1, lhs) + rhs
lhs + basic_string(rhs)
lhs + basic_string(1, rhs)
template<class charT, class traits, class Allocator>
bool
operator==(const basic_string& lhs,
const basic_string& rhs);

Returns a boolean value of true if lhs and rhs are equal, and false if they are not. Equality is defined by the compare() member function.

template<class charT, class traits, class Allocator>
bool
operator==(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
bool
operator==(const basic_string& lhs, const charT* rhs);

Returns a boolean value indicating whether lhs and rhs are equal. Equality is defined by the compare() member function. These functions return, respectively:

basic_string(lhs) == rhs
lhs == basic_string(rhs)
template<class charT, class traits, class Allocator>
bool
operator!=(const basic_string& lhs,
const basic_string& rhs);

Returns a boolean value representing the inequality of lhs and rhs. Inequality is defined by the compare() member function.

template<class charT, class traits, class Allocator>
bool
operator!=(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
bool
operator!=(const basic_string& lhs, const charT* rhs);

Returns a boolean value representing the inequality of lhs and rhs. Inequality is defined by the compare() member function. The functions return, respectively:

basic_string(lhs) != rhs
lhs != basic_string(rhs)
template<class charT, class traits, class Allocator>
bool
operator<(const basic_string& lhs, const basic_string& rhs);

Returns a boolean value representing the lexicographical less-than relationship of lhs and rhs. Less-than is defined by the compare() member.

template<class charT, class traits, class Allocator>
bool
operator<(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
bool
operator<(const basic_string& lhs, const charT* rhs);

Returns a boolean value representing the lexicographical less-than relationship of lhs and rhs. Less-than is defined by the compare() member function. These functions return, respectively:

basic_string(lhs) < rhs
lhs < basic_string(rhs)
template<class charT, class traits, class Allocator>
bool
operator>(const basic_string& lhs, const basic_string& rhs);

Returns a boolean value representing the lexicographical greater-than relationship of lhs and rhs. Greater-than is defined by the compare() member function.

template<class charT, class traits, class Allocator>
bool
operator>(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
bool
operator>(const basic_string& lhs, const charT* rhs);

Returns a boolean value representing the lexicographical greater-than relationship of lhs and rhs. Greater-than is defined by the compare() member. The functions return, respectively:

basic_string(lhs) > rhs
lhs > basic_string(rhs)
template<class charT, class traits, class Allocator>
bool
operator<=(const basic_string& lhs,
const basic_string& rhs);

Returns a boolean value representing the lexicographical less-than-or-equal relationship of lhs and rhs. Less-than-or-equal is defined by the compare() member function.

template<class charT, class traits, class Allocator>
bool
operator<=(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
bool
operator<=(const basic_string& lhs, const charT* rhs);

Returns a boolean value representing the lexicographical less-than-or-equal relationship of lhs and rhs. Less-than-or-equal is defined by the compare() member function. These functions return, respectively:

basic_string(lhs) <= rhs
lhs <= basic_string(rhs)
template<class charT, class traits, class Allocator>
bool
operator>=(const basic_string& lhs,
const basic_string& rhs);

Returns a boolean value representing the lexicographical greater-than-or-equal relationship of lhs and rhs. Greater-than-or-equal is defined by the compare() member function.

template<class charT, class traits, class Allocator>
bool
operator>=(const charT* lhs, const basic_string& rhs);
template<class charT, class traits, class Allocator>
bool
operator>=(const basic_string& lhs, const charT* rhs);

Returns a boolean value representing the lexicographical greater-than-or-equal relationship of lhs and rhs. Greater-than-or-equal is defined by the compare() member. The functions return, respectively:

basic_string(lhs) >= rhs
lhs >= basic_string(rhs)
template <class charT, class traits, class Allocator>
void swap(basic_string<charT,traits,Allocator>& a,
basic_string<charT,traits,Allocator>& b);

Swaps the contents of a and b by calling a抯 swap function on b.

template<class charT, class traits, class Allocator>
basic_istream<charT, traits>&
operator>>(basic_istream<charT, traits>& is,
basic_string& str);

Reads str from is using traits::char_in until a traits::is_del() element is read. All elements read, except the delimiter, are placed in str. After the read, the function returns is.

template<class charT, class traits, class Allocator>
basic_ostream<charT, traits>&
operator<<(basic_ostream <charT, traits>& os,
const<charT, traits allocator> str);

Writes all elements of str to os in order from first to last, using traits::char_out(). After the write, the function returns os.

Non-member Functions

template <class Stream, class charT, class traits,
class Allocator>
basic_istream<charT, traits>
getline(basic_istream<charT, traits> is,
<charT, traits allocator> str, charT delim);

An unformatted input function that extracts characters from is into str until npos - 1 characters are read, the end of the input sequence is reached, or the character read is delim. The characters are read using traits::char_in().

Example

//
// string.cpp
//
#include<string>
#include <iostream>
using namespace std;
int main()
{
string test;
//Type in a string over five characters long
while(test.empty() || test.size() <= 5)
{
cout << "Type a string between 5 and 100 characters long. " << endl;
cin >> test;
}
//Test operator[] access
cout << "Changing the third character from "
<< test[2] << " to * " << endl;
test[2] = '*';
cout << "now its: " << test << endl << endl;

//Try the insertion member function
cout << "Identifying the middle: ";
test.insert(test.size() / 2, "(the middle is here!)");
cout << test << endl << endl;

//Try replacement
cout << "I didn't like the word 'middle',so "
"instead, I'll say:" << endl;
test.replace(test.find("middle",0), 6, "center");
cout << test << endl;
return 0;
}

Program Output

Type a string between 5 and 100 characters long.
roguewave
Changing the third character from g to *
now its: ro*uewave
Identifying the middle: ro*u(the middle is here!)ewave
I didn't like the word 'middle', so instead, I'll say:
ro*u(the center is here!)ewave

[Jagen在路上]

我不知道你是否要的是这个，如果是，你若是不方便，我可以帮你翻译！

[zyq_123]

前辈请你翻译吧！愿好心人一生都平安！

[gloom]

string是C++的标准类吧，String()应该是String类的构造函数，返回一个string类。
你想使用这个类的话，在头文件加入#include不就可以了？你要在控件中使用字符串是什么意思？是说制作自定义控件还是使用控件？

[zyq_123]

[e-mail]
QQ:14633351
我可以和你交个朋友吗？

[zyq_123]

我的程序中需要对字符串进行处理，我要从TXT中读取字符串作了处理写到TDBGrid中，所以要使用strstr()等等一系列的函数。

[gloom]

你是要用指针型字符串的库函数，在程序中的头文件包含就可以了吧，或者在用到的实现文件中加入，不过不能重复包含，否则会出现“Multipe Declare”之类错误

[gloom]

AnsiString 与char* 的转换：
AnsiString-> char* :
char* strA=AnsiStringB.c_str();//注意此处返回的是一个临时指针，最好将字符串COPY后再用。

Char* -> AnsiString：
AnsiString strB=AnsiString(char* strA);

[zyq_123]

头文件应该在什么地方加才合适？

[gloom]

下面是一个示例：
//---------------------------------------------------------------------------

#ifndef CopyFormH
#define CopyFormH
//---------------------------------------------------------------------------
//下面是系统自已加的头文件
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
//你可以在下面加入头文件
#include <string.h>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published: // IDE-managed Components
TEdit *SourceDirEdit;
public: // User declarations
__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

[zyq_123]

整条程序是不是从这里开始的？
//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop
USERES("Project1.res");
USEFORM("Unit1.cpp", Form1);
//---------------------------------------------------------------------------
WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
try
{
Application->Initialize();
Application->CreateForm(__classid(TForm1), &Form1);
Application->Run();
}
catch (Exception &exception)
{
Application->ShowException(&exception);
}
return 0;
}
//---------------------------------------------------------------------------

[gloom]

不是，这是一个程序入口.
比如说，你新建一个Application你什么也不做，只有一个Form,你现在按保存所有Button,就会提示你保存的文件名，第一个出现的是保存Form，接着要保存工程(Project)，你上面的是Project的内容，但我们程序的实现一般是在Form中，我上面贴出来的是一个Form的头文件，一般在Form中双击一个控件就会出现Form的实现文件，而工程的源文件要选Project->ViewSource才会出现。一般除非要对程序做预处理，会加入LOGO画面才对修改Project文件，其它都是在Form中实现，如你的程序中有多个Form，请注意使用string的是哪一个。

[gloom]

你在Form中单击右键，在菜单中选择“OpenSource/HeadFile File”或按Ctrl+F6就会出现此Form的头文件。

[zyq_123]

那整条程序的开头在那里，有没有main()?

[Jagen在路上]

不好意思哦，今天我们开始考试了，要等考完了我才能帮你翻译！！

[过客猫2022]

typedef AnsiString string;

你去看看吧，实际上，String就是AnsiString;