Value Transformer Reference¶

This is the reference documentation for all the NSValueTransformers that Hydrant implements as conveniences for you. Currently, these transformers are intended to be used with HYDMapReflectively.

They are also publicly exposed if you need or prefer to use these classes for other purposes.

HYDBlockValueTransformer¶

This value transformer is a simple abstraction to allow custom blocks instead of having to implement a custom value transformer. The Block Value Transformer simply accepts two blocks: one for transforming and another for reverse transforming.

Due to the limitation of the NSValueTransformer contract, the block value transformer always returns YES for +[allowsReverseTransformation].

Example:

HYDBlockValueTransformer *transformer = [[HYDBlockValueTransformer alloc] initWithBlock:^id(id value){
    return [value componentsSeparatedByString:@"-"];
} reversedBlock:^id(id transformedValue){
    return [value componentsJoinedByString:@"-"];
}];

[transformer transformValue:@"foo-bar"] // => @[@"foo", @"bar"];
[transformer reverseTransformedValue:@[@"foo", @"bar"]] // => @"foo-bar"

HYDIdentityValueTransformer¶

This value transformer is a no-op, simply returning the value it has received. When used with HYDMapReflectively, this can be an easy way to make your objects map directly to the source objects.

Example:

HYDIdentityValueTransformer *transformer = [HYDIdentityValueTransformer new];

[transformer transformValue:@"foo"] // => @"foo"
[transformer reverseTransformedValue:@1] // => @1

HYDReversedValueTransformer¶

This value transformer reverses another value transformer. Essentially, this transformer converts:

-[transformValue:] into -[reverseTransformedValue:]

and -[reverseTransformedValue:] into -[transformValue:]

The given value transformer should be reversable.

HYDCamelToSnakeCaseValueTransformer¶

This value transformer converts camel case to snake case. You can optionally specific if it is UpperCamelCase or lowerCamelCase by specifying one of the following enums:

HYDCamelCaseLowerStyle // default when not specified
HYDCamelCaseUpperStyle

This transformer expects NSStrings. This is useful for HYDMapReflectively to convert snake-cased JSON keys into the more familiar Objective-C style of lower camel-case:

HYDCamelToSnakeCaseValueTransformer *transformer = [[HYDCamelToSnakeCaseValueTransformer alloc] initWithStyle:HYDCamelCaseUpperStyle];

[transformer transformValue:@"foo_bar"] // => @"FooBar"
[transformer reverseTransformedValue:@"FooBar"] // => @"foo_bar"