Replace " in string with \" - objective-c

Question

I am trying to send a string to the server. I encode it and set it as the body of an HTTP request using
[request setHTTPBody:[body dataUsingEncoding:NSUTF8StringEncoding]];
Where body is the string.It has to be in json format.
For example
body = [NSString stringWithFormat:#"{\"emailBody\":\"%#\"}",string] ;
should be valid
But i accept string from user and it may contain double quotes.Therefore i have to escape double quotes(") in it.
For example if want to send just one "
{\"emailBody\":\"\\\"\"}
(harddcoded) returns positive response from server.
So i would like to create such a string from the original string.I tried the following
string = [string stringByReplacingOccurencesOfString:#"\"" withString:#"\\\\\""];
But it did not work.I got \" in my test email.Thats as far as i have been able to get.
Am I taking the right approach ??I would appreciate it if someone would point me in the right direction.Thanks

Answer 1

You should generate your JSON directly from a dictionary. That'll take care of all the encoding automatically for you:
NSDictionary *body = #{#"emailBody": string};
NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:body options:0 error:&error];
if (!jsonData) {
NSLog(#"Got an error: %#", error);
} else {
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
[request setHTTPBody:jsonString];
}