在ViewController里面不能定义protocol么？

[头发还没秃a]

我用Reachability实现个网络监听，不过每个界面都需要实例化Reachability然后调用回调函数，导致有多少个界面就有多少个回调函数在运行好麻烦，所以我想弄个delegate这样每次网络改变不管有多少个界面，监听只回调一次函数，delegate代码写在ViewController文件最上面：

protocol ReachabilityDelegate: class, NSObjectProtocol{
    func WhetherHaveReachability(reachability: Reachability)
}

然后就是在ViewController里面定义：

class ViewController: UIViewController {
    var delegate: ReachabilityDelegate!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.setupReachability()
    }

    func setupReachability() {
        if self.delegate.respondsToSelector("WhetherHaveReachability:") {
            self.delegate.WhetherHaveReachability(reachability)
        }
    }
}

运行的时候var delegate: ReachabilityDelegate!这句报空。。求指教

[qinken547]

weak var delegate:ReachabilityDelegate?

[头发还没秃a]

我用Reachability实现个网络监听，不过每个界面都需要实例化Reachability然后调用回调函数，导致有多少个界面就有多少个回调函数在运行好麻烦，所以我想弄个delegate这样每次网络改变不管有多少个界面，回调函数只调用一次，delegate代码写在ViewController文件最上面：

protocol ReachabilityDelegate: class, NSObjectProtocol{
    func WhetherHaveReachability(reachability: Reachability)
}

然后就是在ViewController里面定义：

class ViewController: UIViewController {
    var delegate: ReachabilityDelegate!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.setupReachability()
    }

    func setupReachability() {
        if self.delegate.respondsToSelector("WhetherHaveReachability:") {
            self.delegate.WhetherHaveReachability(reachability)
        }
    }
}

这样写确实有错误，因为delegate还是为nil的时候，就运行了setupReachability()方法。。。或许我该在viewDidLoad() 里面self.setupReachability()之前先在这个ViewController里面实现定义的delegate？例如：

protocol ReachabilityDelegate: class, NSObjectProtocol{
    func WhetherHaveReachability(reachability: Reachability)
}
class ViewController: UIViewController,ReachabilityDelegate {
    var delegate: ReachabilityDelegate!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
        self.setupReachability()
    }

    func setupReachability() {
        if self.delegate.respondsToSelector("WhetherHaveReachability:") {
            self.delegate.WhetherHaveReachability(reachability)
        }
    }

    func WhetherHaveReachability(reachability: Reachability){
        //实现delegate方法
    }

}

但是这样写还有一个问题，就是其他controller使用不了这个delegate。。。怎么办怎么办？

[三月江城]

设置代理 遵守协议 实现方法

[qinken547]

你的写法不对

[qinken547]

// The protocol to delegate the
// button tap to the ViewController
protocol ButtonDelegate {
    func onButtonTap(sender: UIButton)
}
 
class ViewWithTextAndButton: UIView {
    
    // keeping track of the delegate to use later
    weak var delegate: ButtonDelegate?
    
    func onButtonTap(sender: UIButton) {
        // invoking the delegate when the
        // button is actually tapped
        delegate?.onButtonTap(sender)
    }
}
 
class MyViewController: UIViewController, ButtonDelegate {
    
    let viewWithTextAndButton = ViewWithTextAndButton(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // assigning the delegate
        viewWithTextAndButton.delegate = self
        view.addSubview(viewWithTextAndButton)
    }
    
    // MARK: ButtonDelegate
    // the delegated logic is here
    func onButtonTap(sender: UIButton) {
        print("This button was clicked in the subview!")
    }
 
}

[头发还没秃a]

引用 5 楼 qinken547 的回复:

// The protocol to delegate the
// button tap to the ViewController
protocol ButtonDelegate {
    func onButtonTap(sender: UIButton)
}
 
class ViewWithTextAndButton: UIView {
    
    // keeping track of the delegate to use later
    weak var delegate: ButtonDelegate?
    
    func onButtonTap(sender: UIButton) {
        // invoking the delegate when the
        // button is actually tapped
        delegate?.onButtonTap(sender)
    }
}
 
class MyViewController: UIViewController, ButtonDelegate {
    
    let viewWithTextAndButton = ViewWithTextAndButton(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // assigning the delegate
        viewWithTextAndButton.delegate = self
        view.addSubview(viewWithTextAndButton)
    }
    
    // MARK: ButtonDelegate
    // the delegated logic is here
    func onButtonTap(sender: UIButton) {
        print("This button was clicked in the subview!")
    }
 
}

没办法了，还是直接使用回调了