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Value transformers are not applied on POST body data #1949

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emlynmac opened this issue Jun 11, 2014 · 10 comments · May be fixed by #2475
Closed

Value transformers are not applied on POST body data #1949

emlynmac opened this issue Jun 11, 2014 · 10 comments · May be fixed by #2475
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@emlynmac
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I use NSManagedObjects to replicate a remote endpoint. One of these parameters is passed from the server as BASE64 encoded binary data, which I have implemented a custom NSObject RKValueTransforming class to handle. The API also uses a UNIX time convention, which works well when retrieving the object.

When POSTing back to the server, these values are not transformed, and in some cases will cause a crash in the JSON serialization layer - when it does not adhere to NSCoding.

After digging a little through the code, I see that RKMappingOperations handle the work of transforming the parameters in the - (BOOL)transformValue:(id)inputValue toValue:(__autoreleasing id *)outputValue withPropertyMapping:(RKPropertyMapping *)propertyMapping error: method.

I'm going to see how hard it would be to add this to the outgoing POST requests so that values are transformed on the way out too.
@segiddins
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Create a custom RKValueTransformer for this attribute.

@emlynmac
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I guess the markdown destroyed the part where I said I had a custom RKValueTransformer.

The issue is that the RKValueTransformers are NOT used prior to the JSON serialization layer on the way out. Please re-open the issue, or provide me with a code path to follow 'cas I can't see it.

@segiddins segiddins reopened this Jun 11, 2014
@segiddins
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Please share the code in which you assign the transformer to the mapping?

@emlynmac emlynmac mentioned this issue Jun 11, 2014
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@emlynmac
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The transformer is global:

 // Initialize RestKit
 RKObjectManager *objectManager = [[RKObjectManager alloc] initWithHTTPClient:client];
    objectManager.requestSerializationMIMEType = RKMIMETypeJSON;

    // Add Base64 image transformer
    RKCompoundValueTransformer *valueTransformer = [RKValueTransformer defaultValueTransformer];

    [valueTransformer removeValueTransformer:[RKValueTransformer iso8601TimestampToDateValueTransformer]];
    [valueTransformer addValueTransformer:[MyBase64ImageTransformer new]];

@emlynmac
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Following the code path for creating a POST request, it looks like the issue is in RKObjectParameterization.m

- (BOOL)transformValue:(id)inputValue toValue:(__autoreleasing id *)outputValue withPropertyMapping:(RKPropertyMapping *)propertyMapping error:(NSError *__autoreleasing *)error
{
    if (! inputValue) {
        *outputValue = nil;
        // We only want to consider the transformation successful and assign nil if the mapping calls for it
        return propertyMapping.objectMapping.assignsDefaultValueForMissingAttributes;
    }
    Class transformedValueClass = propertyMapping.propertyValueClass ?: [self.objectMapping classForKeyPath:propertyMapping.destinationKeyPath];
    if (! transformedValueClass) {
        *outputValue = inputValue;
        return YES;
    }
    RKLogTrace(@"Found transformable value at keyPath '%@'. Transforming from class '%@' to '%@'", propertyMapping.sourceKeyPath, NSStringFromClass([inputValue class]), NSStringFromClass(transformedValueClass));
    BOOL success = [propertyMapping.valueTransformer transformValue:inputValue toValue:outputValue ofClass:transformedValueClass error:error];
    if (! success) RKLogError(@"Failed transformation of value at keyPath '%@' to representation of type '%@': %@", propertyMapping.sourceKeyPath, transformedValueClass, *error);
    return success;
}

Issue is in

Class transformedValueClass = propertyMapping.propertyValueClass ?: [self.objectMapping classForKeyPath:propertyMapping.destinationKeyPath];

This consistently returns nil for the value class, so no transform is done. If this returned a NSString class type, then the value transformer should get invoked - if I understand this correctly...

@segiddins
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@blakewatters this should probably change to use a value transformer for everything so it is customizable...

@emlynmac
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I figured out what is up. From the documentation on RKPropertyMapping:

/**
 Specifies the class used to represent the value of the mapped property. A value of `Nil` (which is the default value) indicates the property class is to be determined by runtime introspection.

 In cases where run-time type introspection cannot be performed (such as during object parameterization) you can specify the class used to represent the value of the property being mapped.
 */
@property (nonatomic, strong) Class propertyValueClass;

I was able to set this for value I have, which invokes the value transformer.

@SuperTango
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@emlynmac: Can you post a Gist or something of your final code? I'm trying to do the same thing with a NSURL, and there are a couple of missing pieces that I'm not following.

@rplankenhorn
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@emlynmac Can you elaborate on your fix? I am having a similar issue and can't get my custom transformer to be used at the serialization layer.

@gastonmorixe
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In my case I needed to convert for responses and requests millisecond timestamps. Responses worked by default after set a custom value transformer.

The problem was that it wasn't taken into consideration at request time.

In request mapping I solved it by setting the propertyValueClass as specified above.

[mapping addAttributeMappingsFromDictionary:@{ @"content"               : @"content",
                                               @"messageLocalID"        : @"local_id",
                                               @"createdLocallyAt"      : @"created_locally_at",
                                               }];

[mapping.propertyMappings enumerateObjectsUsingBlock:^(RKAttributeMapping*  _Nonnull attributeMapping, NSUInteger idx, BOOL * _Nonnull stop) {
    if ([attributeMapping.sourceKeyPath isEqualToString:@"createdLocallyAt"]) {
        attributeMapping.propertyValueClass = [NSNumber class];
        *stop = YES;
    }
}];

Custom Value Transformer

- (RKBlockValueTransformer*)timeIntervalSince1970ToDateValueTransformerDouble
{

    if(!_timeIntervalSince1970ToDateValueTransformerDouble){
        _timeIntervalSince1970ToDateValueTransformerDouble = [RKBlockValueTransformer valueTransformerWithValidationBlock:^BOOL(__unsafe_unretained Class inputValueClass, __unsafe_unretained Class destinationClass){

            return ((([inputValueClass isSubclassOfClass:[NSString class]] || [inputValueClass isSubclassOfClass:[NSNumber class]]) && [destinationClass isSubclassOfClass:[NSDate class]]) || ([inputValueClass isSubclassOfClass:[NSDate class]] && ([destinationClass isSubclassOfClass:[NSNumber class]] || [destinationClass isSubclassOfClass:[NSString class]])));

        } transformationBlock:^BOOL(id inputValue,
                                    __autoreleasing id *outputValue,
                                    __unsafe_unretained Class outputClass,
                                    NSError *__autoreleasing *error) {

            static dispatch_once_t onceToken;
            static NSArray *validClasses;
            static NSNumberFormatter *numberFormatter;
            dispatch_once(&onceToken, ^{
                validClasses = @[ [NSNumber class], [NSString class], [NSDate class] ];
                numberFormatter = [NSNumberFormatter new];
                numberFormatter.numberStyle = NSNumberFormatterDecimalStyle;
            });

            RKValueTransformerTestInputValueIsKindOfClass(inputValue, validClasses, error);
            RKValueTransformerTestOutputValueClassIsSubclassOfClass(outputClass, validClasses, error);

            if ([outputClass isSubclassOfClass:[NSDate class]]) {
                if ([inputValue isKindOfClass:[NSNumber class]]) {
                    *outputValue = [NSDate dateWithTimeIntervalSince1970:([inputValue doubleValue] / 1000.0f)];
                } else if ([inputValue isKindOfClass:[NSString class]]) {
                    if ([[inputValue stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0) {
                        *outputValue = nil;
                        return YES;
                    }
                    NSString *errorDescription = nil;
                    NSNumber *formattedNumber;
                    BOOL success = [numberFormatter getObjectValue:&formattedNumber forString:inputValue errorDescription:&errorDescription];
                    RKValueTransformerTestTransformation(success, error, @"%@", errorDescription);
                    *outputValue = [NSDate dateWithTimeIntervalSince1970:[formattedNumber doubleValue]];
                }
            } else if ([outputClass isSubclassOfClass:[NSNumber class]]) {
                *outputValue = @((long long)([inputValue timeIntervalSince1970] * 1000.0f));
            } else if ([outputClass isSubclassOfClass:[NSString class]]) {
                *outputValue = [numberFormatter stringForObjectValue:@([inputValue timeIntervalSince1970])];
            }
            return YES;

        }];
    }

    return _timeIntervalSince1970ToDateValueTransformerDouble;
}

@rafaelnobrepd rafaelnobrepd mentioned this issue Nov 4, 2016
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Inverse transformer introspection devprodoctor/RestKit
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@rplankenhorn @gastonmorixe @SuperTango @segiddins @emlynmac