Automatic Reference Counting: Pointer to non-const type 'NSError *' with no explicit ownership
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25-10-2019 - |
문제
In updating some of my code to be in compatible with the iOS 5 SDK, I attempted to refactor my code by using "Convert to Objective-C ARC" in Xcode and received an error. The error occurs on an instance variable in my .h file.
NSError **_error;
The error says "Pointer to non-const type 'NSError *' with no explicit ownership." How might I fix this?
해결책
When storing NSError
objects in an instance variable you have to declare it as a simple pointer:
@interface Foo : NSObject
{
NSError *_errror;
}
NSError **
is only used to indirectly return NSError
objects from a method to the caller. It is (probably) an error to store it in an instance variable.
다른 팁
You can use one of the lifetime qualifiers described in the Transitioning to ARC Release Notes
For NSError ** you'd use __autoreleasing so the example provided by Nikolai would then look like this
@interface Foo : NSObject
{
NSError * __autoreleasing *error;
}
The syntax is a little weird and you should follow Nikolais advice, but if you're sure NSError ** is what you want this should work.