In the custom delegate implementation, check whether the delegate has implemented the @ protocol method to respond.

In the custom delegate implementation, check whether the delegate has implemented the @ protocol method to respond.
In the custom delegate implementation, we will determine whether the delegate is empty. If not, we will call the corresponding delegate function:
Example: if (delegate _! = Nil)
{
[Delegate _ View: self touchesBegan: touches withEvent: event];
} The above implementation is to determine whether delegate is null. If not, call View: touchesBegan: withEvent: Method of protocol.

However, when a class implements protocol and delegate _ is set as the class object, the class does not implement View: touchesBegan: withEvent: when the method (this method is set to option by protocol), crash will occur.

I thought there was no problem when the option parameter of protocol was set. In fact, it was necessary to determine whether the delegate implemented the protocol method:
The correct code is as follows: if (delegate _! = Nil)
{
If ([(NSObject *) delegate _ respondsToSelector: @ selector (foolTapView: touchesBegan: withEvent:)] = YES)
{
[Delegate _ View: self touchesBegan: touches withEvent: event];
}
}
RespondsToSelector is an NSObject method, so the delegate must be forcibly converted to NSObject
*.