使用dispatch_async的EXC_BAD_ACCESS

发布于 2024-10-31 01:33:48 字数 943 浏览 2 评论 0原文

我正在尝试通过 Objective-C++ 中的异步调度队列执行块。这是我正在尝试执行的操作的类片段...

class Blah {
public:
    void dispatch(const EventPtr& event) {
        dispatch_queue_t queue = dispatch_queue_create(_queueName.c_str(), NULL);
        dispatch_async(queue, ^{
            this->dispatchEventToSubscribers(event); 
        });
        dispatch_release(queue);
    }
protected:
    Dude _dude;
    void dispatchEventToSubscribers(const EventPtr& event) {
        _dude.dispatchToSubscribers(event);
    }
}

我在dispatchEventToSubscribers 方法中获得了EXC_BAD_ACCESS。当我检查 _dude 的值时，XCode 告诉我它超出了范围。我只能假设我正在以某种方式失去this。检查并发文档：

对于您计划执行的块使用调度队列异步，捕获标量变量是安全的来自父函数或方法并且在块中使用它们。然而，你不应该尝试捕获大结构体或其他基于指针的分配的变量和被调用上下文删除。由当你的块被执行时，该指针引用的内存可能走吧。当然，这是安全的分配内存（或对象）自己并明确地交出该内存对该块的所有权。

那么如何在 this 对象上异步分派方法呢？

谢谢！

原文

I'm attempting to execute a block via an asynchronous dispatch queue in Objective-C++. Here's a class fragment of what I'm trying to do...

class Blah {
public:
    void dispatch(const EventPtr& event) {
        dispatch_queue_t queue = dispatch_queue_create(_queueName.c_str(), NULL);
        dispatch_async(queue, ^{
            this->dispatchEventToSubscribers(event); 
        });
        dispatch_release(queue);
    }
protected:
    Dude _dude;
    void dispatchEventToSubscribers(const EventPtr& event) {
        _dude.dispatchToSubscribers(event);
    }
}

I get a EXC_BAD_ACCESS within the dispatchEventToSubscribers method. When I check to see what the value of _dude is, XCode tells me it is out of scope. I can only assume that I'm losing this somehow. Checking the concurrency docs:

For blocks that you plan to perform
asynchronously using a dispatch queue,
it is safe to capture scalar variables
from the parent function or method and
use them in the block. However, you
should not try to capture large
structures or other pointer-based
variables that are allocated and
deleted by the calling context. By the
time your block is executed, the
memory referenced by that pointer may
be gone. Of course, it is safe to
allocate memory (or an object)
yourself and explicitly hand off
ownership of that memory to the block.

So how do I dispatch asynchronously a method on this object?

Thanks!

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凉月流沐 2024-11-07 01:33:48

由于某种原因，制作 event 的本地实例有效...我不知道为什么...即..

void dispatch(const EventPtr& event) {
    dispatch_queue_t queue = dispatch_queue_create(_queueName.c_str(), NULL);
    EventPtr eventPtr = event;  //local instance...
    dispatch_async(queue, ^{
        this->dispatchEventToSubscribers(eventPtr); 
    });
    dispatch_release(queue);
}

For some reason, making a local instance of event worked...I'm not sure why...i.e...

void dispatch(const EventPtr& event) {
    dispatch_queue_t queue = dispatch_queue_create(_queueName.c_str(), NULL);
    EventPtr eventPtr = event;  //local instance...
    dispatch_async(queue, ^{
        this->dispatchEventToSubscribers(eventPtr); 
    });
    dispatch_release(queue);
}

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