IOS uses block to implement function callbacks

In fact, the block in iOS is a function pointer in C + +, the implementation is the same way, a simple practice is posted below.

First, create a callback class

BlockStudy.h

  blockstudy.h//  blockstudy////  Created by du Jia Li on 11/11/14.//  Copyright (c) 2014 DuPont. All rights reserved.//#import <Foundation/Foundation.h> @interface blockstudy:nsobjecttypedef Void (^testblock) (); @property (nonatomic, Strong) Testblock testblock;-(void) startblock; @end

Blockstudy.m

  blockstudy.m//  blockstudy////  Created by du Jia Li on 11/11/14.//  Copyright (c) 2014 DuPont. All rights reserved.//#import "BlockStudy.h" @implementation blockstudy-(void) test{    if (_testblock) {        _ Testblock ();    }} -(void) startblock{    [self performselector: @selector (Test) Withobject:nil afterdelay:2.0];} @end

Call Class VIEWCONTROLLER.M

  viewcontroller.m//  blockstudy////  Created by du Jia Li on 11/11/14.//  Copyright (c) 2014 DuPont. All rights reserved.//#import "ViewController.h" #import "BlockStudy.h" @interface Viewcontroller () @ End@implementation viewcontroller-(void) viewdidload {    [super viewdidload];    Additional setup after loading the view, typically from a nib.    Blockstudy *block = [[Blockstudy alloc] init];    Block.testblock = ^ ()    {        Uialertview *alert = [[Uialertview alloc] initwithtitle:@ "Block learning" message:@ "Test succeeded" Delegate:self cancelbuttontitle:@ "Cancel" otherbuttontitles:@ "OK", nil];        [Alert show];            };    [Block Startblock];} -(void) didreceivememorywarning {    [super didreceivememorywarning];    Dispose of any resources the can be recreated.} @end

IOS uses block to implement function callbacks