使用块回调时如何释放对象
这可能是关于内存管理的新手问题。
在 Objective C 中使用块作为回调时如何释放对象？
（更新的代码）
@implementation ObjectWithCallback
- (void)dealloc {
[_completionHandler release];
[super dealloc];
}
- (void)doTaskWithCompletionHandler:(void(^)(void))handler {
_completionHandler = [handler copy];
// Start tasks...
}
- (void)tasksDone {
// Do callback block
_completionHandler();
// Delete reference to block
[_completionHandler release];
_completionHandler = nil;
}
// Use of the ObjectWithCallback
ObjectWithCallback *request = [[ObjectWithCallback alloc] init];
[request doTaskWithCompletionHandler:^(void){
// Callback called and task is ready.
}];
this is probably a newbie question regarding memory manegment.
How can i release an object when using blocks as callback in objective c?
(Updated code)
@implementation ObjectWithCallback
- (void)dealloc {
[_completionHandler release];
[super dealloc];
}
- (void)doTaskWithCompletionHandler:(void(^)(void))handler {
_completionHandler = [handler copy];
// Start tasks...
}
- (void)tasksDone {
// Do callback block
_completionHandler();
// Delete reference to block
[_completionHandler release];
_completionHandler = nil;
}
// Use of the ObjectWithCallback
ObjectWithCallback *request = [[ObjectWithCallback alloc] init];
[request doTaskWithCompletionHandler:^(void){
// Callback called and task is ready.
}];
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快速、不完整的答案：
[request autorelease]这样做的问题是块隐式保留块体内引用的任何对象。因此，该块保留了
request，而request保留了该块，从而导致保留周期并且没有人被释放。为了解决这个问题，您可以将
request变量声明为__block，这可以防止块保留捕获的对象：推荐阅读：
Quick, incomplete answer:
[request autorelease]The problem with this is that blocks implicitly retain any objects that are referenced inside the body of the block. So the block retains
request, andrequestretains the block, leading to a retain cycle and nobody getting deallocated.To remedy that, you declare your
requestvariable as__block, which prevents the block from retaining the captured object:Recommended reading: