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Apple's iOS documentation on NSMutableURLRequest says:

NSURLConnection makes a deep copy of each NSMutableURLRequest object passed to one of its initializers.

How is this implemented? I don't see any documented way of performing deep copy of NSMutableURLRequest objects. Field by field copying is not good enough, as NSMutableURLRequest can be subclassed.

My use case: I'm implementing NSURLProtocol for a custom protocol built on top of http. My NSURLProtocol implementation will do its custom stuff, then use NSURLConnection with a slightly modified NSURLRequest.

noamtm
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    NSMutableURLRequest implements the NSCopying and NSMutableCopying protocols, you probably should use the copy methods to create a deep copy – Felix Nov 20 '12 at 21:32
  • @phix23: `copy` does not ordinarily perform a deep copy. – Peter Hosey Nov 20 '12 at 22:41
  • I tested NSURLConnection and found that it does not create a copy of the request at all. I used the properties originalRequest and currentRequest and logged them with NSLog(@"request: %p", request). – Felix Nov 20 '12 at 23:03
  • @phix23 it only copies the mutable variant. Which have you tested? In my tests it created an immutable copy of my mutable request. – noamtm Nov 21 '12 at 04:52

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When you want to make deep copies of objects you can use NSKeyedArchiver.

Basically use NSKeyedArchiver to save the object into a NSData object

Load it back with NSKeyedUnarchiver

Pochi
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  • That's apparently not what it uses - I created an NSMutableURLRequest subclass and overrid all the methods for NSCopying, NSMutableCopying and NSCoding (along with a few other random guesses), and none of those are called. So it's either using something very propertiary (and thus possibly not safe to subclass) or the docs are inaccurate and it's not actually making copies. I doubt it's the latter. – Wade Tregaskis Nov 21 '12 at 05:58
  • I am not sure of what you mean, but I didn't say NSCopying uses this. I'm saying that you can use this to make a deep copy. I don't even understand why you would override those methods, they are class dependent and will copy the properties that are considered relevant in each class, which is why the result differs depending on which you use it on. – Pochi Nov 21 '12 at 06:12
  • @WadeTregaskis: it possible that you're right and it's not safe to subclass; I just noticed that the docs say if you want to add properties for your custom protocol you should do so "using NSURLProtocol’s propertyForKey:inRequest: and setProperty:forKey:inRequest: methods". As for actually making copies: copies *are* made, that's for sure. – noamtm Nov 21 '12 at 12:09
  • @LuisOscar my question kind-of implied that I want to know what "they" do. In reality however your answer *does* answer the question in the title, although it seems like NSMutableCopying will solve my particular problem in a better way. – noamtm Nov 21 '12 at 12:13
  • @noamtm i thought you had already tried that method and you were not still getting everything you wanted. the diference between copying and doing this one is that when you copy you "immitate" the object, this one really copies everything it has. nsmutablecopy is not a deep copy though. – Pochi Nov 21 '12 at 13:22
  • @LuisOscar haven't tried it before, I somehow missed the NSMutableCopying stuff. But like I wrote in the above comment, I didn't really need a deep copy; still, I think I'll accept your answer because it's good to know. – noamtm Nov 21 '12 at 14:43