Question

如何创建自己的方法，将块作为参数并稍后调用？

我试过以下事情。

#import <UIKit/UIKit.h>
typedef void (^viewCreator)(void);

@interface blocks2ViewController : UIViewController
{
}
-(void)createButtonUsingBlocks:(viewCreator *)block;

@end


- (void)viewDidLoad {
  [super viewDidLoad];
  [self createButtonUsingBlocks:^(NSString * name) {
        UIButton *dummyButton = [[UIButton alloc]initWithFrame:CGRectMake(50, 50, 200, 100)];
        dummyButton.backgroundColor = [UIColor greenColor];
        [self.view addSubview:dummyButton];
  }];
}

-(void)createButtonUsingBlocks:(viewCreator *)block
{
    //    Do something
    NSLog(@"inside creator");
}

我也尝试将块变量传递给我的自定义方法但没有任何成功。为什么会这样呢？这样做的正确方法是什么？

更新

这是文件is.h：

 #import <UIKit/UIKit.h>

typedef void (^viewCreator)(void);

@interface blocks2ViewController : UIViewController
{

}
- (void)createButtonUsingBlocks:(viewCreator)block;
@end

这是.m文件：

#import "blocks2ViewController.h"

@implementation blocks2ViewController
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
        [self createButtonUsingBlocks:^(NSString * name) {
        UIButton *dummyButton = [[UIButton alloc]initWithFrame:CGRectMake(50, 50, 200, 100)];
        dummyButton.backgroundColor = [UIColor greenColor];
        [self.view addSubview:dummyButton];
        [dummyButton release];
    }];
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

// ...

-(void)createButtonUsingBlocks:(viewCreator)block
{
//    viewCreator;
    NSLog(@"inside creator");
}
@end

Answer 1

首先如果你想让你的块采用字符串参数，那么typedef是关闭的：

typedef void (^viewCreator)(NSString*);

其次块的类型是：

ReturnType (^)(ParameterTypes...)

而不是

ReturnType (^*)(ParameterTypes...)

因此无需添加指向viewCreator类型的指针：

- (void)createButtonUsingBlocks:(viewCreator)block;

第三次如果你还没有这样做，你实际上必须调用该块：

-(void)createButtonUsingBlocks:(viewCreator *)block {
    block(@"button name");
    // ...

第四，最后，UIButton被过度保留 - 您应release或autorelease：

UIButton *dummyButton = [[UIButton alloc] initWithFrame:...];
// ...    
[self.view addSubview:dummyButton];
[dummyButton release];

投掷所有这些：

#import <UIKit/UIKit.h>
typedef void (^viewCreator)(NSString*);

@interface blocks2ViewController : UIViewController {}
-(void)createButtonUsingBlocks:(viewCreator)block;      
@end

@implementation blocks2ViewController
- (void)viewDidLoad {
    [super viewDidLoad];  
    [self createButtonUsingBlocks:^(NSString *name) {
        UIButton *dummyButton = 
            [[UIButton alloc] initWithFrame:CGRectMake(50, 50, 200, 100)];
        dummyButton.backgroundColor = [UIColor greenColor];
        [self.view addSubview:dummyButton];
        [dummyButton release];
    }];
}

-(void)createButtonUsingBlocks:(viewCreator)block {
    block(@"my button name");
}
@end

Answer 2

您也可以这样做而无需预先定义方法：

@interface blocks2ViewController : UIViewController
-(void)createButtonUsingBlocks:(void (^)(NSString *name))block;
@end

- (void)viewDidLoad {
    [super viewDidLoad];
    [self createButtonUsingBlocks:^(NSString * name) {
        UIButton *dummyButton = [[UIButton alloc]initWithFrame:CGRectMake(50, 50, 200, 100)];
        dummyButton.backgroundColor = [UIColor greenColor];
        [self.view addSubview:dummyButton];
    }];
}

-(void)createButtonUsingBlocks:(void (^)(NSString *name))block
{
    block(@"My Name Here");
}

我如何创建自己的方法，将块作为参数，以后可以调用？

2 个答案: