一段代码的疑惑,请指教!!!!
下面这段代码,我对psf这个私有成员变量很不理解,为什么它的类型是类本省呢?这样做有什么好处?
/// <summary>
/// factory pentru IPersistenceService
/// </summary>
public class PersistenceServiceFactory
{
private static PersistenceServiceFactory psf = null;
private static IPersistenceService ps = null;
private PersistenceServiceFactory(){}
public static PersistenceServiceFactory GetInstance()
{
if(psf==null)
{
psf = new PersistenceServiceFactory();
}
return psf;
}
public static IPersistenceService getPS()
{
return GetInstance().getPersistenceService();
}
public static IPersistenceService getPS(string connectionString)
{
return GetInstance().getPersistenceService(connectionString);
}
private IPersistenceService getPersistenceService()
{
if(ps==null)
{
ps = new PersistenceServiceImpl();
}
return ps;
}
private IPersistenceService getPersistenceService(string connectionString)
{
if(ps==null)
{
ps = new PersistenceServiceImpl(connectionString);
}
return ps;
}
}