Calling an instance method when subclassing NSURLProtocol

Question

So I've had to subclass NSURLProtocol because I am using a UIWebView and want to intercept ajax calls which works fine as per this example. I have to get the data from the request from + (BOOL)canInitWithRequest:(NSURLRequest *)request which causes a problem, I now need to call instance methods to do things with the data, but I can't because it's a class method.

How could I call an instance method based on the contents of what is in the request?

Do these methods you need to call need to access instance variables or can you refactor those methods so they are in turn class methods? — DarkDust, Aug 08 '13 at 07:45

score 0 · Answer 1 · answered Aug 08 '13 at 11:35

You cannot call instance methods from a class method without having an instance first. This is true for all object-oriented systems, AFAIK. After all, the instance methods (usually) use data that the class method cannot have. Imagine an object with a property name, and you now have one thousand objects with different names. How should the class method know which name to use?

So you need to find a way to somehow query instances of your class based on your request, or find a way to get at the information in a way that does not involve instance variables (if a method doesn't use instance variable you can turn it into a class method or even C function). There are many different ways to solve the "query problem", which to chose is highly dependent on your design and even taste.

score 0 · Answer 2 · answered Mar 31 '14 at 08:49

0

canInitWithRequest: shouldn't do any work whatsoever, it should just respond with "YES" or "NO". "startLoading" is where you do the work.

answered Mar 31 '14 at 08:49

gnasher729

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Calling an instance method when subclassing NSURLProtocol

2 Answers2