How to handle unexpected data types with Mantle

Question

In my MTLModel subclass I have this:

@property (assign, nonatomic) NSInteger catId;

And of course this in the implementation:

+ (NSDictionary *)JSONKeyPathsByPropertyKey {
    return @{

             @"catId" : @"cat_id"

             };

}

But what if my server friends decide to change cat_id to a string in the JSON response? How can I handle this case, and convert it to an int so that I don't get Mantle errors?

Answer 1

if([obj isKindOfClass:NSClassFromString(@"__NSCFNumber")])
{
//if it is int or number
}
else
{

}

May be above method will help you

Answer 2

We also used Mantle for quite some time, but at the end migrated to handwritten parser/serializers, as the task itself seem to be trivial.

Though, we also have this kind of problems: what if server return something we do not expect (e.g. NSDictionary instead of NSString).

To prevent our app from crashing we use this simple tool: Fuzzer.

Basically the tool provides a method that takes a sample and a block. The block evaluates several times, each time bringing slightly mutated version of the sample. You can check behaviour of the models/parsers/serializers using the mutants, to ensure that your code handles unexpected data gracefully.

Here is example taken from project's README:

- (void)test {
  NSDictionary *sample = @{
    @“name” : @“John Doe”,
    @“age” : @42
  };

  UserDeserializer *deserializer = [UserDeserializer new];

  FZRRunner *runner = [FZRRunner runnerWithBuiltinMutationsForSample:sample];

  NSArray *reports = [runner enumerateMutantsUsingBlock:^(NSDictionary *mutant) {
    [deserializer deserializeUser:mutant];
  }];

  XCTAssertEqual(reports.count, 0);
}