cocoa - 如何将 GCD 对象放入 CF 集合(CFArray、CFDictionary)中？

Question

部署目标是10.6，因此需要手动内存管理。该集合应该负责保留/释放 GCD 对象。

我相信 CFDictionary 的 CFArray 的自定义回调会有所帮助，但是我正在寻找一个简单的、经过充分测试的解决方案

Answer 1

回调和集合创建非常简单:

static const void * dispatchObjectRetainCallBack(CFAllocatorRef allocator, const void *value)
{
    if (value) {
        dispatch_retain(value);
    }
    return value;
}

static void dispatchObjectReleaseCallBack(CFAllocatorRef allocator, const void *value)
{
    if (value) {
        dispatch_release(value);
    }
}

CFMutableArrayRef CreateDispatchHoldingArray()
{
    CFArrayCallBacks callBacks = {
        0,
        dispatchObjectRetainCallBack,
        dispatchObjectReleaseCallBack,
        NULL,
        NULL
    };
    return CFArrayCreateMutable(kCFAllocatorDefault, 0, &callBacks);
}

CFMutableDictionaryRef CreateDispatchHoldingDictionary()
{
    CFDictionaryValueCallBacks valueCallBacks = {
        0,
        dispatchObjectRetainCallBack,
        dispatchObjectReleaseCallBack,
        NULL,
        NULL
    };
    return CFDictionaryCreateMutable(kCFAllocatorDefault, 0, &kCFTypeDictionaryKeyCallBacks, &valueCallBacks);
}

稍微棘手的部分是将 dispatch_object_t 放入和取出集合。您不能简单地将 dispatch_object_t 类型的变量转换为 void *，因为 dispatch_object_t 是联合的 typedef。编译器报错:

Operand of type 'dispatch_object_t' where arithmetic or pointer type is required

您必须遍历 dispatch_object_t 内的联合类型之一，如下所示:

void AddDispatchObjectToArray(CFMutableArrayRef array, dispatch_object_t obj)
{
    void* voidPtrObj = obj._do;
    CFArrayAppendValue(array, voidPtrObj);
}

dispatch_object_t GetDispatchObjectAtIndex(CFMutableArrayRef array, CFIndex index)
{
    dispatch_object_t result;
    result._do = (struct dispatch_object_s *)CFArrayGetValueAtIndex(array, index);
    return result;
}