IOS開發之Block，iosblock

IOS開發之Block，iosblock
IOS開發之Block1.什麼是block，block的作用

　　UI開發和網路常見功能實現回調，按鈕的事件處理方法是回調方法，網路下砸後的回調處理

　　（1）按鈕target-action  一個方法傳入按鈕中

　　（2）表格視圖   傳入一個指標self，回調視圖控制器重的方法

　　（3）block　　 語句塊，解決回調，理解為“匿名函數”，這個函數定義在方法裡面

 

2.block的基本使用（文法）

　　定義block變數

　　定義block語句塊

//block 理解匿名函數    //void func（）    //{    //}        //1.block變數的定義    //技巧:   文法詭異帶來男鞋的問題    //void func（）;        //定義block變數,^表示定義block    //技巧:  函數名左右家括弧，在函數名前面加^    void (^block)();        //定義block語句塊,儲存到block變數中    block = ^void ()    {        NSLog(@"I am block");    };        //執行    block();

　　block參數和傳回值

 //2.帶有參數和傳回值block    //執行個體    實現計算兩數之和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捕獲外部變數

　　block的注意事項

@interface ViewController (){    int _page;}@property (copy,nonatomic) NSString *url;@end //3.block是捕獲外部變數    //  block使用block外面的變數的注意事項        int num = 10;    __block int val = 100;    void (^bbbb)() = ^void()    {        //能使用和修改執行個體變數        _page = 1;                // block中不能修改局部變數的值，但可以使用        //num++;                //block中能修改__block修飾的局部變數        val++;                //有可能有警告，因為記憶體問題引起，注意//        __weak typeof(self) weakSelf = self;//        weakSelf.url = @"text";        self.url = @"text";            };    bbbb();

 3.block在開發中應用（OC，UI，網路）

1.NSMutableArray排序

2.UIView動畫

3.block實現介面反向傳值

-(void)blockDelelopApply{    //oc中的應用    //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動畫    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(10, 200, 100, 100)];    label.text = @"kkkk";    label.backgroundColor = [UIColor redColor];    [self.view addSubview:label];        //向下移動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實現介面反向傳值        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];        //設定block    [svc setChangeBackGroundColor:^(NSString *color) {        if ([color isEqualToString:@"blue"]) {            self.view.backgroundColor = [UIColor blueColor];        }    }];                [self presentViewController:svc animated:YES completion:nil];}

　　反向傳值:

　　　　a.在第二個介面設定block

//為了給第二個介面傳入block-(void)setChangeBackGroundColor:( void (^)(NSString *color) )action;//@property (nonatomic,copy) setChangeBackGroundColor ( void (^__)(NSString *__color) );

　　　　b.第二個介面實現block

@interface SecondViewController (){    //定義block變數，為了儲存傳入的參數    void (^_action)(NSString *color);}@end@implementation SecondViewController-(void)setChangeBackGroundColor:(void (^)(NSString *))action{    _action = action;}

　　　　c.第二個介面給block賦值

 //改變住介面的顏色    if (_action) {        _action(@"blue");    }

　　　　d.第一個介面設定block

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

//設定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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