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我对块和 objective-c很新,我试图用两者写我的第一个类别.我的想法是在NSTimer上创建一个类别,它将接收一个块作为参数,这个块将用于选择器调用.现在我有这个.

// NSTimer+Additions.h

#import <Foundation/Foundation.h>

typedef void (^VoidBlock)();

@interface NSTimer (NSTimer_Additions)


+ (NSTimer *)scheduleTimerWithTimeInterval:(NSTimeInterval)theseconds repeats:(BOOL)repeats actions:(VoidBlock)actions;
@end

#import "NSTimer+Additions.h"

static VoidBlock _voidBlock;

@interface NSTimer (AdditionsPrivatE) // Private stuff
- (void)theBlock;
@end


@implementation NSTimer (NSTimer_Additions)


+ (NSTimer *)scheduleTimerWithTimeInterval:(NSTimeInterval)theseconds repeats:(BOOL)repeats actions:(VoidBlock)actions {

    [_voidBlock release];
    _voidBlock = [actions copy];

    NSTimer* timer = [[NSTimer alloc] initWithFireDate:[NSDate date] 
                                          interval:theseconds
                                            target:self 
                                          SELEctor:@SELEctor(theBlock) 
                                          userInfo:nil 
                                           repeats:repeats];
    [timer fire];

    return [timer autorelease];
}


- (void)theBlock {
    _voidBlock();
}

@end

代码要点：https://gist.github.com/1065235

一切都编译好但我有以下错误：

2011-07-05 14：35：47.068 TesteTimer [37716：903] *由于未捕获的异常’NSInvalidArgumentexception’终止应用程序,原因：'[NSTimer theBlock]：无法识别的选择器发送到类0x7fff70bb0a18′

我该如何使这个类别工作？

解决方法

除了错误的目标之外,你的主要缺陷是你使用静态变量.除了一个计时器,你将无法支持.

使用block作为被调用方法的参数.

@interface NSTimer (AdditionsPrivatE) // Private stuff
- (void)theBlock:(VoidBlock)voidBlock;
@end


@implementation NSTimer (NSTimer_Additions)

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)theseconds repeats:(BOOL)repeats actions:(VoidBlock)actions {
    NSInvocation * invocation = [NSInvocation invocationWithMethodSignature:[self instanceMethodSignatureForSELEctor:@SELEctor(theBlock:)]];
    NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:theseconds
                                                   invocation:invocation
                                                      repeats:repeats];
    [invocation setTarget:timer];
    [invocation setSELEctor:@SELEctor(theBlock:)];

    Block_copy(actions);
    [invocation setArgument:&actions aTindex:2];
    Block_release(actions);

    return timer;
}


- (void)theBlock:(VoidBlock)voidBlock {
    voidBlock();
}

@end

使用关联引用的问题是泄漏,因为释放块没有好处.

早期的方法使用关联参考

您可以使用associative references将块附加到该特定NSTimer实例.

@implementation NSTimer (NSTimer_Additions)

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)theseconds repeats:(BOOL)repeats actions:(VoidBlock)actions {
    NSInvocation * invocation = [NSInvocation invocationWithMethodSignature:[self instanceMethodSignatureForSELEctor:@SELEctor(theBlock)]];
    NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:theseconds
                                                   invocation:invocation
                                                      repeats:repeats];
    [invocation setTarget:timer];
    [invocation setSELEctor:@SELEctor(theBlock)];

    objc_setAssociatedObject(timer,@"Block",actions,OBJC_ASSOCIATION_COPY);

    return timer;
}


- (void)theBlock {
    VoidBlock _voidBlock = (VoidBlock)objc_getAssociatedObject(self,@"Block");
    _voidBlock();
}

@end