iOS block常见用法

1.首先看看block的定义

返回值类型 (^blockName)(参数列表) = ^返回值类型 (参数类型 参数名) { // ... 
};
blockName(var);

2.block当做对象的属性

@property(nonatomic, copy) 返回值类型(^属性名)(参数列表);

///1️⃣ block当做属性(无返回值，无参）
@property(nonatomic, copy) void(^test1Block)(void);
///2️⃣ block当做属性（无返回值，有参数）
@property(nonatomic, copy) void(^test2Block)(NSString *Str1,NSString *Str2);

3.block当做OC方法的参数

- (void)methodName:(返回值类型(^)(参数类型 *参数名))block名;
 // 其中参数名可省略，为了在引用的时候能自动添加，最好写上

@interface ViewController : UIViewController

/// 3️⃣ block当做方法的参数（无返回值无参数）
- (void)method1:(void(^)(void))block1;
/// 4️⃣ block当做方法的参数（无返回值有参数）
- (void)method2:(void(^)(NSString *str1,NSString *str2))block2;
/// 5️⃣ block当做方法的参数（有返回值有参数）
- (void)method3:(NSString *(^)(NSString *str1, NSString *str2))block3;
@end

4.使用typedef定义block

typedef void(^compleBlock)(void);
@interface ViewController : UIViewController

@property(nonatomic, copy) compleBlock test1;
- (void)method4:(compleBlock)test2;
@end

1.常见用法

进行回调

@interface SecondViewController : UIViewController

@property(nonatomic, copy) void(^test1Block)(void);
- (void)method2:(void(^)(NSString *str1,NSString *str2))block2;
@property(nonatomic, copy) void(^block3)(NSString *str1,NSString *str2);
@end

@implementation SecondViewController
- (IBAction)test3Click:(UIButton *)sender {
    if (self.test1Block) {
        self.test1Block();
    }
}

- (void)method2:(void (^)(NSString * _Nonnull, NSString * _Nonnull))block2 {
    
    NSLog(@"block2 = %@",block2);
    if (block2) {
        self.block3 = ^(NSString *str1, NSString *str2) {
            block2(str1,str2);
        };
//      self.block3 = block2;
    }
}

- (IBAction)test4Click:(UIButton *)sender {
    if (self.block3) {
        self.block3(@"abc", @"123efg");
    }
}
@end

//******************************************
#import "SecondViewController.h"
@implementation ViewController

- (IBAction)test1Click:(UIButton *)sender {
    SecondViewController *secondVC = [[UIStoryboard storyboardWithName:@"Main" bundle:nil] instantiateViewControllerWithIdentifier:@"secondVC"];
    
    secondVC.test1Block = ^{
        NSLog(@"收到了seconVC 的 block1 属性回调");
    };
    
    [secondVC method2:^(NSString * _Nonnull str1, NSString * _Nonnull str2) {
        NSLog(@"从secondVC的method2方法中返回的 str1 = %@，str2 = %@",str1, str2);
    }];
    
    [self.navigationController pushViewController:secondVC animated:YES];
}

@end

2.进行链式编程

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface NumberManager : NSObject

@property(nonatomic, copy) NumberManager*(^add)(CGFloat number);

@property(nonatomic, copy) NumberManager*(^multiply)(CGFloat number);

@property(nonatomic, assign) CGFloat resultNumber;
//- (instancetype)
@end

NS_ASSUME_NONNULL_END

@implementation NumberManager

- (NumberManager * _Nonnull (^)(CGFloat))add {
    
    __weak typeof(self) weakSelf = self;
    return  ^NumberManager * _Nonnull(CGFloat number) {
        weakSelf.resultNumber += number;
        return weakSelf;
    };
}

- (NumberManager * _Nonnull (^)(CGFloat))multiply {
    __weak typeof(self) weakSelf = self;
    
    return  ^NumberManager * _Nonnull(CGFloat number) {
        weakSelf.resultNumber *= number;
        return weakSelf;
    };
}

@end

调用

#import "NumberManager.h"
@implementation ViewController
- (IBAction)test2Click:(UIButton *)sender {
    
    NumberManager *testManager = [[NumberManager alloc] init];
    
    testManager.add(123).multiply(4).add(5).multiply(2);
    
    NSLog(@"结果=%f",testManager.resultNumber);
}
@end

2019-05-27 16:31:42.278 LearnBlock[3062:659032] 结果=994.000000

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