How to specify child objects type in an NSArray wi

问题:

If I have a dictionary like

{
  name: "Bob",
  cars: [
    { make: "ford", year: "1972" },
    { make: "mazda", year: "2000" }
  ],
}

and two models like:

@interface CarModel : MTLModel

@property (nonatomic, strong) NSString *make;
@property (nonatomic, strong) NSString *year;

@end

@interface PersonModel : MTLModel

@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSArray *cars;

@end

How do I use Mantle so that my array of cars in my person model are CarModels?

回答1:

Ah figured it out. I needed to add a private method:

+ (NSValueTransformer *)carsTransformer
{
    return [NSValueTransformer mtl_externalRepresentationArrayTransformerWithModelClass:[CarModel class]];
}

and make sure I used:

[PersonModel modelWithExternalRepresentation:dict];

回答2:

+[NSValueTransformer mtl_externalRepresentationArrayTransformerWithModelClass:] is deprecated. The new API is +[NSValueTransformer mtl_JSONArrayTransformerWithModelClass:].

After switching to the new API, the models can be initialized with the default initializers provided by, e.g., MTLJSONAdapter.

回答3:

A note on:

[NSValueTransformer mtl_JSONArrayTransformerWithModelClass:CarModel.class];

This methods seems to now be deprecated. I'm using this new method in my code and it appears to be working just fine:

[MTLJSONAdapter arrayTransformerWithModelClass:CarModel.class];

回答4:

+ (NSValueTransformer *)carsJSONTransformer {
    return [NSValueTransformer mtl_JSONArrayTransformerWithModelClass:CarModel.class];
}

Read more here

回答5:

+[NSValueTransformer mtl_JSONArrayTransformerWithModelClass:]

This method is deprecated. New method is:

  + (NSValueTransformer *)carsTransformer
    {
        return [MTLJSONAdapter arrayTransformerWithModelClass:[CarsModel class]];
    }