Converting iOS5 app to ARC

Question

I am integrating some third party code into my app, and at the same time, trying to convert the app to ARC.

I'm attaching a screen shot to show the only two errors. If this is obvious to someone how to recode this section, I would be most grateful.

enter image description here

I have one more pita to solve. What's the most pragmatic way to solve this one:

value =  (NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(kCFAllocatorDefault,
                                                                                             (CFStringRef)value,
                                                                                             CFSTR(" "),
                                                                                             kCFStringEncodingUTF8);

This gives this error:

"Cast of Objective-C pointer type 'NSString *' to C pointer type 'CFStringRef' (aka 'const struct __CFString *') requires a bridged cast"

Thanks again.. I will lose this code asap...

Fabian Kreiser Fabian Kreiser · Accepted Answer · 2011-11-06T19:10:40

You shouldn't use -performSelector: anyway. Use objc_msgSend(target, selector, ...) instead. If you call -respondsToSelector: you can just use [vc setDelegate:self.delegate] after the if-statement. The same is true for the first line. Replace it with:

UIViewController *vc = [vcClass alloc]; // vc = [[vcClass alloc] initWithSomething:[specifier file] ...]; if the initSelector is known at compile time

If the initSelector is dynamically generated:

objc_msgSend(vc, initSelector, [specifier file], ...);

Hope this helps.

Update: Answer to the second question

If you transfer CF objects to Objective-C objects, ARC needs to know how the memory management is handled. You have to insert __bridge, __bridge_retained or __bridge_transfer before the cast:

NSString *value;
value = (__bridge_transfer NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(kCFAllocatorDefault, (__bridge CFStringRef)value, CFSTR(" "), kCFStringEncodingUTF8);

You use __bridge if you only want to cast between CF and Objective-C, __bridge_retained if it's a retained value and you handle that later using CFRelease and __bridge_transfer if you want to transfer the object from CF to Objective-C or vice-versa.

Converting iOS5 app to ARC

3 Answers