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 <Foundation/Foundation. h> // class declaration @ class button; // <> indicates implementing a protocol, nsobject is the underlying protocol // buttondelegate is the protocol name @ protocol buttondelegate <nsobject>-(void) onclick :( button *) But; @ end @ interface button: nsobject // nonatomic does not require multi-thread management. delegate is the button listener @ property (nonatomic, retain) ID <buttondelegate> 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 <Foundation/Foundation. h> # import "button. H "// declare the protocol in advance. The role of @ class is the same as that of @ protocol buttondelegate; @ interface buttonlisterner: nsobject <buttondelegate> @ 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;}