Get JSON string for my object with RestKit - ios

Question

I want to create a json string to save in NSUserDefaults and then get it back from it.
I've already added RestKit to my project, to send and receive objects from the server.
However, now i want to flatten and save the data.
How do i use restkit to get a JSON string of my object?

Answer 1

I needed the same functionality (in my case to send he JSON as a multipart attribute), so after a while searching, I get the solution.
You can get the JSON data (and JSON string) using RestKit with that code, you have to pass the object you want to convert, and the mapping you want to use to convert.
RKRequestDescriptor *descriptorObject = ...
Custom *object = ...
NSDictionary *parametersForObject = [RKObjectParameterization parametersWithObject:object requestDescriptor:descriptorObject error:nil];
NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:parametersForObject
options:NSJSONWritingPrettyPrinted //Pass 0 if you don't care about the readability of the generated string
error:&error];
NSString *jsonString;
if (! jsonData) {
NSLog(#"Got an error: %#", error);
}
else {
jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}
I have not find this documented, I just find it browsing the code, I am not sure if it is a public API or a private one. At least, it works for RestKit 0.20

Answer 2

You generally don't. RestKit serialises to JSON only as part of a network communication. In this case you're converting from an internal to external data format. In your case you want an internal data format stored for a while. In this case it's easier to just use NSJSONSerialization. To do this you do need to create a dictionary / array and then use dataWithJSONObject:options:error:.
Technically, to do what you ask you would use RKMappingOperation. This is done using the initWithSourceObject:destinationObject:mapping:, where the source object is the dictionary created from the JSON (JSONObjectWithData), the destination object is a new instance of the object targeted by the mapping and the mapping is your mapping to use.