Handling NSAsserts in Restkit throws

I am using Restkit's object manager to handle a good chunk of my remote API calls.

It throws NSAssert for a wide range of errors. For example, if the server returns a error page as opposed to well-formed JSON, it will raise an NSAssert, even if there is nothing wrong with the code.

There are a few things I am confused about (most of which has to do 开发者_Go百科with general handling of exceptions and nsasserts).

1. How should we handle these NSAsserts errors? For example, we would want to retry again for a few times, then show a "something went wrong" message (as opposed to crashing the application).

2. I tried to use a catch-try block to catch the errors (code below), but the errors are not being caught. So my app just keeps failing. Furthermore, I am not comfortable using try-catch in release mode anyway.

3. Just for my understanding, why do Restkit use NSAsserts, as opposed to other failure?

Code:

// code to catch NSAssert that sharedManager throws
@try{
    [sharedManager loadObjectsAtResourcePath:self.resourcePath delegate:self];
}

@catch (NSException *ex) {
    NSLog(@"exception caught");
}

In general, you should NOT try to catch NSAssert errors, as they mean that something went horribly wrong - e.g. an application internal state become inconsistent, your are using library incorrectly etc., - and so application needs to quit.[1]

The reason your errors are not being caught is because NSAssert raises an NSInternalInconsistencyException[2], which is a string and not an instance of NSException. You can still catch them as per[3], e.g. with

    @catch (id ex)

but it's not recommended for the reasons listed above.

To answer your 3rd question, please provide more details around which NSAssert is raised etc.

[1] What's the point of NSAssert, actually?

[2] http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_Functions/Reference/reference.html#//apple_ref/c/macro/NSAssert

[3] http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Exceptions/Tasks/HandlingExceptions.html