ios 块而不是 performSelector:withObject:afterDelay:
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Blocks instead of performSelector:withObject:afterDelay:
提问by Rits
I often want to execute some code a few microseconds in the future. Right now, I solve it like this:
我经常想在未来几微秒内执行一些代码。现在，我是这样解决的：
- (void)someMethod
{
// some code
}
And this:
和这个：
[self performSelector:@selector(someMethod) withObject:nil afterDelay:0.1];
It works, but I have to create a new method every time. Is it possible to use blocks instead of this? Basically I'm looking for a method like:
它有效，但我每次都必须创建一个新方法。是否可以使用块来代替这个？基本上我正在寻找一种方法，如：
[self performBlock:^{
// some code
} afterDelay:0.1];
That would be really useful to me.
那对我真的很有用。
回答by John Calsbeek
There's no built-in way to do that, but it's not too bad to add via a category:
没有内置的方法可以做到这一点，但通过类别添加还不错：
@implementation NSObject (PerformBlockAfterDelay)
- (void)performBlock:(void (^)(void))block
afterDelay:(NSTimeInterval)delay
{
block = [[block copy] autorelease];
[self performSelector:@selector(fireBlockAfterDelay:)
withObject:block
afterDelay:delay];
}
- (void)fireBlockAfterDelay:(void (^)(void))block {
block();
}
@end
Credit to Mike Ashfor the basic implementation.
归功于Mike Ash的基本实现。
回答by Nick Moore
Here's a simple technique, based on GCD, that I'm using:
这是我正在使用的基于 GCD 的简单技术：
void RunBlockAfterDelay(NSTimeInterval delay, void (^block)(void))
{
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC*delay),
dispatch_get_current_queue(), block);
}
I'm not a GCD expert, and I'd be interested in comments on this solution.
我不是 GCD 专家，我对对此解决方案的评论很感兴趣。
回答by ninjaneer
Another way (perhaps the worst way to do this for many reasons) is:
另一种方法（可能出于多种原因是最糟糕的方法）是：
[UIView animateWithDuration:0.0 delay:5.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{
} completion:^(BOOL finished) {
//do stuff here
}];
回答by Greg Combs
If you specifically need a longer delay, the solutions above work just fine. I've used @nick's approach with great success.
如果您特别需要更长的延迟，上述解决方案就可以正常工作。我已经成功地使用了@nick 的方法。
However, if you just want your block to run during the next iteration of the main loop, you can trim it down even further with just the following:
但是，如果您只想让您的块在主循环的下一次迭代中运行，您可以使用以下命令进一步减少它：
[[NSOperationQueue mainQueue] addOperationWithBlock:aBlock];
This is akin to using performSelector: with afterDelay of 0.0f
这类似于使用 performSelector: with afterDelay 0.0f
回答by Despotovic
I used similar code like this:
我使用了类似的代码：
double delayInSeconds = 0.2f;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
//whatever you wanted to do here...
});
回答by Duane Fields
There's a nice, complete category that handles this situation here:
这里有一个很好的完整类别可以处理这种情况：
