Protocol in Objective-C

Protocol in Objective-C

Protocol in Objective-C

Protocol

In short, it is a list of methods. The declared methods can be implemented by any class. This mode is generally called the (delegation) mode.

In iOS and OS X, Apple uses a large number of proxy modes to implement View (UI control) and Controller (Controller) in MVC)

The following is an example.

Declare a Button class and a Buttonlisterner class

In the Button. h file

# Import
 
  
// Class declaration @ class Button; // <> indicates implementing a protocol. NSObject is the underlying protocol. // ButtonDelegate is the protocol name @ protocol ButtonDelegate
  
   
-(Void) onClick :( Button *) but; @ end @ interface Button: NSObject // nonatomic does not require multi-thread management. delegate is the Button listener @ property (nonatomic, retain) id
   
    
Delegate;-(void) Click; @ end
   
  
 

In the Button. m file

# Import "Button. h "@ implementation Button //-(void) dealloc {// [super dealloc]; //}-(void) click {NSLog (@ "Click button is clicked... "); // If there is an onClick: method, call this method if ([_ delegate respondsToSelector: @ selector (onClick :)]) {// and tell the listener which button has been clicked [_ delegate onClick: self];} @ end

In the Buttonlisterner. h file

# Import
 
  
# Import "Button. h" // declare the protocol in advance. The role of @ class is the same as that of @ protocol ButtonDelegate; @ interface Buttonlisterner: NSObject
  
   
@ End
  
 

In the Buttonlisterner. m file

#import "Buttonlisterner.h"#import "Button.h"@implementation Buttonlisterner-(void)onClick:(Button *)but{    NSLog(@"onClick...");}@end

In main. m

int main(int argc, const char * argv[]){    @autoreleasepool {        Button* button = [[Button alloc]init];        Buttonlisterner* listenter = [[Buttonlisterner alloc]init];        button.delegate=listenter;        [button Click];                }    return 0;}