IOS开发之Block

IOS开发之Block

1.什么是block,block的作用

  UI开发和网络常见功能实现回调,按钮的事件处理方法是回调方法,网络下砸后的回调处理

  (1)按钮target-action  一个方法传入按钮中

  (2)表格视图   传入一个指针self,回调视图控制器重的方法

  (3)block   语句块,解决回调,理解为“匿名函数”,这个函数定义在方法里面

 

2.block的基本使用(语法)

  定义block变量

  定义block语句块

//block 理解匿名函数
    //void func()
    //{
    //}
    
    //1.block变量的定义
    //技巧:   语法诡异带来男鞋的问题
    //void func();
    
    //定义block变量,^表示定义block
    //技巧:  函数名左右家括号,在函数名前面加^
    void (^block)();
    
    //定义block语句块,存储到block变量中
    block = ^void ()
    {
        NSLog(@"I am block");
    };
    
    //执行
    block();

  block参数和返回值

 //2.带有参数和返回值block
    //实例    实现计算两数之和block
//    int myAdd(int x ,int y);
    
    int (^myAdd)(int x ,int y) = ^int (int x ,int y)
    {
        return x+y;
    };
    int s = myAdd(10,20);
    NSLog(@"s = %d",s);

 

  block捕获外部变量

  block的注意事项

@interface ViewController (){

    int _page;
}

@property (copy,nonatomic) NSString *url;
@end


 //3.block是捕获外部变量
    //  block使用block外面的变量的注意事项
    
    int num = 10;
    __block int val = 100;
    void (^bbbb)() = ^void()
    {
        //能使用和修改实例变量
        _page = 1;
        
        // block中不能修改局部变量的值,但可以使用
        //num++;
        
        //block中能修改__block修饰的局部变量
        val++;
        
        //有可能有警告,因为内存问题引起,注意
//        __weak typeof(self) weakSelf = self;
//        weakSelf.url = @"text";
        self.url = @"text";
        
    };
    bbbb();

 

3.block在开发中应用(OC,UI,网络)

1.NSMutableArray排序

2.UIView动画

3.block实现界面反向传值

-(void)blockDelelopApply{
    //oc中的应用
    //1.NSMutableArray排序
    
    Dog *ahua = [[Dog alloc]init];
    ahua.nikeName = @"ahua";
    ahua.age = 4;
    
    Dog *amiao = [[Dog alloc]init];
    amiao.nikeName = @"amiao";
    amiao.age = 3;
    
    Dog *dahuang = [[Dog alloc]init];
    dahuang.nikeName = @"dahuang";
    dahuang.age = 5;
    
    NSMutableArray *marr = [[NSMutableArray alloc]initWithArray:@[ahua,amiao,dahuang]];
    //marr sortUsingSelector:<#(SEL)#>
    [marr sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        Dog *aDog = obj1;
        Dog *bDog = obj2;
//        return aDog.age > bDog.age;
        return [aDog.nikeName compare:bDog.nikeName] > 0;
    }];
    
    for (Dog *d  in marr) {
        NSLog(@"name = %@,age = %d",d.nikeName,d.age);
    }
    
    //2.UIView动画
    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(10, 200, 100, 100)];
    label.text = @"kkkk";
    label.backgroundColor = [UIColor redColor];
    [self.view addSubview:label];
    
    //向下移动200
//    [UIView animateWithDuration:<#(NSTimeInterval)#> animations:<#^(void)animations#>]
    [UIView animateWithDuration:2 animations:^{
        CGRect frame = label.frame;
        frame.origin.x +=200;
        label.frame = frame;
    } completion:^(BOOL finished) {
        NSLog(@"finish");
        
        [UIView animateWithDuration:1 animations:^{
            label.transform = CGAffineTransformMakeRotation(M_PI);
        } completion:^(BOOL finished) {
            [UIView animateWithDuration:2 animations:^{
                label.frame = CGRectMake(10, 200, 100, 100);
                label.transform = CGAffineTransformMakeRotation(M_PI);

            }];
            
        }];
    }];
    
    //3.block实现界面反向传值
    
    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    button.frame = CGRectMake(0, 20, 320, 10);
    [button setTitle:@"change" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonact:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    
}

-(void)buttonact:(UIButton *)but{

    SecondViewController *svc = [[SecondViewController alloc]init];
    
    //设置block
    [svc setChangeBackGroundColor:^(NSString *color) {
        if ([color isEqualToString:@"blue"]) {
            self.view.backgroundColor = [UIColor blueColor];
        }
    }];
    
    
    
    [self presentViewController:svc animated:YES completion:nil];
}

  反向传值:

    使用block实现界面传值

    若有两个界面A界面, B界面, A界面创建B界面, B界面值传递到A界面

    A界面设置block,B界面保存block

      a.在第二个界面定义block

//为了给第二个界面传入block
-(void)setChangeBackGroundColor:( void (^)(NSString *color) )action;

//@property (nonatomic,copy) setChangeBackGroundColor ( void (^__)(NSString *__color) );

      b.第二个界面实现block

@interface SecondViewController (){
    //定义block变量,为了保存传入的参数
    void (^_action)(NSString *color);
}

@end

@implementation SecondViewController

-(void)setChangeBackGroundColor:(void (^)(NSString *))action{
    _action = action;
}

      c.第二个界面给block赋值

 //改变住界面的颜色
    if (_action) {
        _action(@"blue");
    }

      d.第一个界面设置block


    SecondViewController *svc = [[SecondViewController alloc]init];

//设置block
    [svc setChangeBackGroundColor:^(NSString *color) {
        if ([color isEqualToString:@"blue"]) {
            self.view.backgroundColor = [UIColor blueColor];
        }
    }];

    [self presentViewController:svc animated:YES completion:nil];


 

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