Objective-C learning Notes use protocols to implement callback Functions

Objective-CLearning notes UtilizationProtocolImplement callbackFunctionIs the content to be introduced in this article, mainly to implement a display text as a test view, and then after 3 seconds to test the text into a callbackFunctionText. The response is as follows:

 

The implementation code is as follows:

Definition protocol:

 
 

  
  
# Import <UIKit/UIKit. h>
  
  
@ Protocol NoteDelegate
  
  
// Callback function
  
  
-(Void) messageCallBack :( NSString *) string;
  
  
@ End
 
 

Call Protocol:

 
 

  
  
# Import <Foundation/Foundation. h>
  
  
# Import "NoteDelegate. h"
  
  
@ Interface ManagerMessage: NSObject {
  
  
Id <NoteDelegate> * noteDelegate;
  
  
}
  
  
@ Property (nonatomic, retain) id <NoteDelegate> * noteDelegate;
  
  
-(Void) startThread;
  
  
@ End
  
  
 
  
  
# Import "ManagerMessage. h"
  
  
@ Implementation ManagerMessage
  
  
@ Synthesize noteDelegate;
  
  
// Start a thread
  
  
-(Void) startThread
  
  
{
  
  
 
  
  
[NSTimer scheduledTimerWithTimeInterval: 3
  
  
Target: self
  
  
Selector: @ selector (targetMethod :)
  
  
UserInfo: nil
  
  
Repeats: NO];
  
  
}
  
  
-(Void) targetMethod :( NSString *) string
  
  
{
  
  
If (self. noteDelegate! = Nil ){
  
  
// Complete the callback function called by the thread
  
  
[Self. noteDelegate messageCallBack: @ "callback function"];
  
  
}
  
  
}
  
  
@ End
 
 

Foreground page implementation:

 
 

  
  
# Import "IphoneDeleteViewController. h"
  
  
# Import "ManagerMessage. h"
  
  
@ Implementation IphoneDeleteViewController
  
  
@ Synthesize textView;
  
  
 
  
  
// Callback function
  
  
-(Void) messageCallBack :( NSString *) string
  
  
{
  
  
Self. textView. text = string;
  
  
}
  
  
-(Void) viewDidLoad {
  
  
[Super viewDidLoad];
  
  
Self. textView. text = @ "test ";
  
  
ManagerMessage * message = [[ManagerMessage alloc] init];
  
  
// Notification Call Protocol
  
  
Message. noteDelegate = self;
  
  
[Message startThread];
  
  
[Message release];
  
  
}
  
  
-(Void) didReceiveMemoryWarning {
  
  
[Super didReceiveMemoryWarning];
  
  
}
  
  
-(Void) viewDidUnload {
  
  
Self. textView = nil;
  
  
}
  
  
-(Void) dealloc {
  
  
[Self. textView release];
  
  
[Super dealloc];
  
  
}
  
  
@ End
 
 

Summary: The introduction of Objective-C learning notes using the Protocol to implement callback functions is complete. I hope this article will help you.