iOS Block

block语法在iOS中应用越来越广，今天大致讲一下Block的用法，主要以回调为主。

大致分几个步骤实现：(以写一个BUtton的回调来说)

1⃣️：声明一个Block和暴露一个接口给外面，并且定义一个property

#import <UIKit/UIKit.h>
//声明一个Block
typedef void (^myBlock)(void);
@interface NewButton : UIButton
@property(nonatomic,strong)myBlock block;
//暴露一个接口给外面
-(void)addTarget:(id)target Andaction:(myBlock)block forControlEvents:(UIControlEvents)controlEvents;
@end

2⃣️：实现方法，并在button被点击的时候触发这个Block。

#import "NewButton.h"

@implementation NewButton

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    
    return self;
}

-(void)addTarget:(id)target Andaction:(myBlock)block forControlEvents:(UIControlEvents)controlEvents{
    
    
    _block = block;
    [self addTarget:self action:@selector(editBtn:) forControlEvents:UIControlEventTouchUpInside];
}

-(void)editBtn:(id)sender{
    
    _block();
}

3⃣️：调用Button，触发回调。

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	
    
    NewButton *button = [NewButton buttonWithType:UIButtonTypeRoundedRect];
    button.backgroundColor = [UIColor greenColor];
    [button setTitle:@"Pressed" forState:UIControlStateNormal];
    [button setFrame:CGRectMake(110, 100, 100, 100)];
    
    [self.view addSubview:button];
    
    [button addTarget:self Andaction:^{
        
        NSLog(@"PRESSED");
    } forControlEvents:UIControlEventTouchUpInside];
}

[self addTarget:self action:@selector(editBtn:) forControlEvents:UIControlEventTouchUpInside];

这个addTarget：后面是Self，而不是Target，这个Mark一下，纠结我20分钟，蛋碎。