NSTimer永远不会触发

Question

我一直有问题让NSTimer触发，我认为它必须解决多线程问题。为了确保正确创建计时器，我创建了以下测试代码，并将其放入我的主视图控制器的initWithNibName中。令我惊讶的是，它也未能在那里开枪。

NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:@selector(timerTest:paramTwo:paramThree:)]]; 
NSString *a = @"a"; 
NSString *b = @"b"; 
NSString *c = @"c"; 
[invocation setArgument:&a atIndex:2]; //indices 0 and 1 are target and selector respectively, so params start with 2 
[invocation setArgument:&b atIndex:3]; 
[invocation setArgument:&c atIndex:4]; 
[[NSRunLoop mainRunLoop] addTimer:[NSTimer timerWithTimeInterval:5 invocation:invocation repeats:NO] forMode:NSDefaultRunLoopMode]; 

任何关于这段代码有什么问题的线索？它似乎完成文档指定的NSInvocation与NSTimer的使用。

Answer 1

NSInvocations也必须有一个目标，并且除了一个方法签名和参数的选择：

NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:@selector(timerTest:paramTwo:paramThree:)]]; 
NSString *a = @"a"; 
NSString *b = @"b"; 
NSString *c = @"c"; 
[invocation setArgument:&a atIndex:2]; //indices 0 and 1 are target and selector respectively, so params start with 2 
[invocation setArgument:&b atIndex:3]; 
[invocation setArgument:&c atIndex:4]; 
[invocation setTarget:self]; 
[invocation setSelector:@selector(timerTest:paramTwo:paramThree:)]; 
[[NSRunLoop mainRunLoop] addTimer:[NSTimer timerWithTimeInterval:1 invocation:invocation repeats:NO] forMode:NSDefaultRunLoopMode];