Convert null values to NSNull using the array transformer

[mantle]

Convert null values to NSNull using the array transformer

[jspahrsummers]

CC @ursachec @orta

[orta]

Think this makes sense to me. 👍

[ursachec]

pretty and 👍

[akashivskyy]

yep 👍

[wlisac]

Is there a recommended way to opt out of this behavior?

My current solution is to subclass MTLJSONAdapter.

+ (NSValueTransformer<MTLTransformerErrorHandling> *)arrayTransformerWithModelClass:(Class)modelClass
{
    NSValueTransformer<MTLTransformerErrorHandling> *transformer = [super arrayTransformerWithModelClass:modelClass];

    return [MTLValueTransformer transformerUsingForwardBlock:^id(id value, BOOL *success, NSError *__autoreleasing *error) {
        NSArray *models = [transformer transformedValue:value success:success error:error];
        if ([models containsObject:[NSNull null]]) {
            if (error != NULL) {
                NSDictionary *userInfo = @{ NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert JSON array to model array", @""),
                                            NSLocalizedFailureReasonErrorKey: NSLocalizedString(@"Array contained a null object. This is not supported.", nil) };

                *error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
            }
            *success = NO;
            return nil;
        }
        return models;
    } reverseBlock:^id(id value, BOOL *success, NSError *__autoreleasing *error) {
        if ([transformer respondsToSelector:@selector(reverseTransformedValue:success:error:)]) {
            return [transformer reverseTransformedValue:value success:success error:error];
        }
        return nil;
    }];
}

[robb]

That seems like a sensible approach to me 👍