(POST Request) Parse JSON elements from a URL response in Objective-C - ios

Question

I am having trouble with parsing/returning JSON from a URL response. Here is an example
lets say I submit this to a server [POST not GET]
firstname=first&lastname=last&age=99
and the response from the server is this
{
"person":{
"firstname":"first",
"lastname":"last",
"info":{
"age":"99"
}
}
}
how would I retrieve this information (certain elements)
lets say I JUST want the persons age so the return string should be just "99"
or how do I JUST return the lastname or JUST the firstname, another thing how would I pass the returned element into the next POST request without the user having to type it again?
if anyone can find an example that would be fantastic :)
Thank You!

Answer 1

lets say the name of this data is json (you called it response). This is a dictionary. What this means is that it has key/value pairs. To access it do the following:
To get any of this information in the dictionary, all you need is a one line of code!!
To get detail of a person's first name,
[response valueForKeyPath:#"person.firstname"];
To get last name :
[response valueForKeyPath:#"person.lastname"];
To get age :
[response valueForKeyPath:#"person.info.age"];

Answer 2

Hmm... If it were me, I would just get the NSDictionary, then look inside the NSDictionary.
To get age:
You would want to get { "firstname":"first", "lastname":"last", "info":{ "age":"99" } }, so do:
[responseObject objectForKey:#"person"];
After you do that, you would want to get { "age":"99" }. To do that, you should use
[[responseObject objectForKey:#"person"]objectForKey:#"info"];
After that, 1 last step to get the value for age:
[[[responseObject objectForKey:#"person"]objectForKey:#"info"]objectForKey:#"age"];
And then, you have age.
To get firstname
Just find the object for key firstname by doing:
[[responseObject objectForKey:#"person"]objectForKey:#"firstname"];
To get lastname
[[responseObject objectForKey:#"person"]objectForKey:#"lastname"];
... The rest should follow the same rule.
How to pass it back to a POST request
Well, the POST request takes in an id parameters. This is where you would put the dictionary. To do this correctly without having to deal with any asynchrony, you would have to make the POST request inside the GET request. For example:
[manager GET:<your GET url>
parameters:nil
success:^(AFHTTPRequestOperation *operation, id responseObject) {
[manager POST:<your POST url>
parameters:responseObject
success:^(AFHTTPRequestOperation *operation, id responseObject) { NSLog(#"Success!"); }
failure:^(AFHTTPRequestOperation *operation, NSError *error) { NSLog(#"Error: %#", error); }];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) { NSLog(#"Error: %#", error); }];
Well, that's pretty much it. Hope this helped :)