Having trouble retaining a CGPath object (warning appears)
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I have an instance variable `CGMutablePathRef _mutablePath` which I set as `@property (nonatomic) CGMutablePathRef mutablePath;` . I override the setter method:

    - (void) setMutablePath:(CGMutablePathRef)mutablePath
    {
        if (_mutablePath)
        {
            CGPathRelease(_mutablePath);
            _mutablePath = NULL;
        }
        
        _mutablePath = CGPathRetain(mutablePath);
    }

However I am getting a warning on this line: `_mutablePath = CGPathRetain(mutablePath);` that says:

    Assigning to 'CGMutablePathRef' (aka 'struct CGPath *') from 'CGPathRef' (aka 'const struct CGPath *') discards qualifiers

Why would this not work? This seems to work with CT (core text) objects when I do it. I've tried a bunch of different casts but can't get the error to go away, any advice would be appreciated.