How to get same JSON string output on iOS and Rails? - objective-c

Question

I have a JSON document on iOS and an identical document in Rails. When I serialize it on iOS, I need it to be character-for-character equivalent to the serialized string from Rails. However, when I try this, the outputs are mostly the same, but not quite.
On iOS:
id jsonObj;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonObj options:0 error:nil];
NSString *string = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
On the Ruby side:
jsonObj // contains exactly the same content as the objc version
string = JSON.generate(jsonObj)
The issue I'm having is that Ruby's JSON.generate() doesn't output a JSON string in the same format as NSJSONSerialization on iOS. Is there any way to make them behave the same? Or is there another serialization method I can use to get consistent results on iOS and Rails?
One difference between the two that I spotted was that the original object had the text "N/A" in it. Rails outputs this as-is, while iOS escapes it to "N\ /A". Is there another string encoding option I can use on the iOS side to fix this?
Edit:
Here's a better example:
id json = #{ #"str": #"N/A" };
NSError *error = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:json options:0 error:&error];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
NSLog(#"jsonString = '%#'", jsonString);
// prints "jsonString = '{"str":"N\/A"}'"
And the ruby equivalent:
json = { "str" => "N/A" }
jsonString = JSON.generate(json)
puts "jsonString = '#{jsonString}'"
// prints "jsonString = '{"str":"N/A"}'"
I also wrote both outputs to files and compared them again, with the same results.