Objective-C 块参数

Objective-C 块参数是一种非常有用的语言特性，它允许我们在代码中以一种简洁、灵活的方式传递和使用代码块。块参数可以作为函数的参数、变量或属性的值，使得我们能够以一种更加直观和便捷的方式处理异步操作、自定义回调和事件处理等场景。

objective-c
- (void)sendRequestWithURL:(NSURL *)url completion:(void (^)(NSData *data, NSError *error))completionBlock {
    NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        if (error) {
            completionBlock(nil, error);
        } else {
            completionBlock(data, nil);
        }
    }];
    [task resume];
}

objective-c
typedef void (^CompletionBlock)(NSInteger result);
@interface Calculator : NSObject
- (void)add:(NSInteger)num1 to:(NSInteger)num2 completion:(CompletionBlock)completionBlock;
@end
@implementation Calculator
- (void)add:(NSInteger)num1 to:(NSInteger)num2 completion:(CompletionBlock)completionBlock {
    NSInteger result = num1 + num2;
    completionBlock(result);
}
@end

objective-c
Calculator *calculator = [[Calculator alloc] init];
[calculator add:2 to:3 completion:^(NSInteger result) {
    NSLog(@"2 + 3 = %ld", (long)result);
}];

objective-c
typedef void (^ButtonActionBlock)(UIButton *button);
@interface ButtonViewController : UIViewController
@property (nonatomic, strong) UIButton *button;
@property (nonatomic, copy) ButtonActionBlock buttonActionBlock;
@end
@implementation ButtonViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.button = [[UIButton alloc] initWithFrame:CGRectMake(100, 100, 100, 40)];
    [self.button setTitle:@"Click Me" forState:UIControlStateNormal];
    [self.button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [self.button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.button];
}
- (void)buttonClicked:(UIButton *)button {
    if (self.buttonActionBlock) {
        self.buttonActionBlock(button);
    }
}
@end

objective-c
ButtonViewController *viewController = [[ButtonViewController alloc] init];
viewController.buttonActionBlock = ^(UIButton *button) {
    NSLog(@"Button Clicked: %@", button.titleLabel.text);
};