How to declare optional property in Mantle? - ios

Question

Specific situation detail:
In my current photo app, There are such situation : allow user experience first without log in,
but no have some field(e.g:voted,purchased ,etc) in the JSON responded from backend. If user logged in,
the field is added in JSON .
I'll show off my implement details as following:
PhotoListResponseModel (directly inherit MTLModel)
#interface PhotoListResponseModel : MTLModel <MTLJSONSerializing>
...
#property (nonatomic, copy, readonly) NSNumber *foo;
#property (nonatomic, copy, readonly) NSArray<PhotoModel *> *subPhotos;
#end
#interface PhotoModel : MTLModel <MTLJSONSerializing>
#property (nonatomic, copy, readonly) NSNumber *photoID;
#property (nonatomic, copy, readonly) NSURL *imageUrl;
...
#end
#implementation PhotoListResponseModel
+ (NSDictionary *)JSONKeyPathsByPropertyKey {
return #{#"foo": #"foo"
#"subPhotos": #"photos"
};
}
+ (NSValueTransformer *)subPhotosJSONTransformer {
return [MTLJSONAdapter arrayTransformerWithModelClass:PhotoModel.class];
}
#end
#implementation PhotoModel
+ (NSDictionary *)JSONKeyPathsByPropertyKey {
return #{
#"photoID": #"id",
#"userID": #"user_id",
};
}
#end
Correspondly, the JSON example as following:
noAuthPhoto.json
{
"foo": 1,
"photos": [
{
"id": 204748881,
"image_url": "https://foo1/bar1",
},
{
"id": 204996257,
"image_url": "https://foo2/bar2"
}
],
…
…
}
AuthedPhoto.json
{
"foo": 1,
"photos": [
{
"id": 204748881,
"image_url": "https://foo1/bar2”,
"voted": false,
"purchased": false
},
{
"id": 204996257,
"image_url": "https://foo2/bar2”,
"voted": false,
"purchased": false
}
],
...
...
}
So, how let new field can compatible my already existing code?
Optional Property? (I not know how to do this.)
Or add a subclass of inherit from PhotoListResponseModel & PhotoModel?
Or any good idea : )
Update: I noticed this information,but still don't know how to do it.

Answer 1

Optional properties are only available in Swift, but similar idea for the Obj-C — objects with possible nil value — should work well. You can add the following NSNumber properties to your PhotoModel:
#property (nonatomic, strong) NSNumber *voted;
#property (nonatomic, strong) NSNumber *purchased;
And assign your BOOL values from parsed JSON during PhotoModel object creation like this:
photoModelObject.voted = [NSNumber numberWithBool:[parsedJson valueForKey:#"voted"]];
photoModelObject.purchased = [NSNumber numberWithBool:[parsedJson valueForKey:#"purchased"]];
Next, when you reference your photo object, just check if these properties have nil value. If they are — your user is not logged in and you don't need to show them. Otherwise, extract BOOL value from them like this:
if (photoModelObject.voted && photoMobelObject.purchased) {
BOOL isVoted = [photoModelObject.voted boolValue];
BOOL isPurchased = [photoModelObject.purchased boolValue];
// Use booleans to present info for registered users
} else {
// There is no info about votes and purchasing provided for the current user
}