手动释放 NSValue
是否可以使用指向 C 结构的指针实例化 NSValue 而无需创建自动释放池？目前，我这样做：
NSValue* val = [NSValue valueWithPointer:(const void*)structure];
但这是由自动释放池释放的。我想控制它并能够在需要时释放它。这可能吗？我尝试过这个：
NSValue* value = [[NSValue alloc] initWithBytes:(const void*)structure objCType:@encode(const void*)];
[value release];
但由于某种原因它崩溃了。还有什么办法可以立即释放吗？ 谢谢！
Is it possible to instantiate a NSValue with a pointer to a C structure without having to create a autorelease pool? For the moment, I do this:
NSValue* val = [NSValue valueWithPointer:(const void*)structure];
but this is release by the autorelease pool. I would like to take control of this and be able to dealloc it when I want. Is this possible? I tried this:
NSValue* value = [[NSValue alloc] initWithBytes:(const void*)structure objCType:@encode(const void*)];
[value release];
but it is crashing for some reason. Any other way to be able to release immediately?
Thanks!
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您应该传递一个指向为 objCType: 参数指定的类型的指针。您正在传递类型的变量。因此，例如，如果您想将变量
int foo存储在 NSValue 中，则可以编写[[NSValue alloc] initWithBytes:&foo objCType:@encode( int)]。因此，如果要存储指针，则需要将指针作为字节传递给该指针。传递指针本身将导致 NSValue 尝试跟随指针，然后将其指向的字节也视为指针。You're supposed to be passing a pointer to the type that's given for the
objCType:argument. You're passing a variable of the type. So, for example, if you have a variableint foothat you want to store in an NSValue, you'd write[[NSValue alloc] initWithBytes:&foo objCType:@encode(int)]. So if you want to store a pointer, you need to pass a pointer to that pointer as the bytes. Passing the pointer itself will cause NSValue to try to follow the pointer and then treat the bytes that it's pointing to as a pointer as well.