Parse relation string - ios

Question

I'm developing an iOS app to parse data
I have a class called #"name" this class contains a string column [name]
and a class called #"email" this class contains a string column[email]
the class are already related and no have problem with that
In a different ViewController have two TextField and one button, on a TextField the user enters a valid name string (name)
The button display should show in the second TextField the email associated with the name entered. I want to associate this data.
//relation class
PFObject *data = [PFObject objectWithClassName:#"nameContactMe"];
data[#"name"] = _name.text;
PFObject *DataRequest = [PFObjec objectWithClassName:#"mailContactMe"];
DataRequest[#"email"] = _email.text;
DataRequest[#"relation"] = data;
[DataRequest saveInBackground];
here the disaster
//get relation
- (IBAction)GetDate:(id)sender {
PFRelation *relation = [user relationForKey:#"relation"];
[user saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
if (succeeded) {
// The post has been added to the user's likes relation.
} else {
// There was a problem, check error.description
}
}];
PFObject *data = _Visitor.text = #"relation";
[data fetchIfNeededInBackgroundWithBlock:^(PFObject *post, NSError *error) {
emailField.text = data[#"email"];
// do something with your title variable
}];
}

Answer 1

I think you should use PFQuery for fetching the desired email :
PFQuery *query = [PFUser query];
[query whereKey:#"name" equalTo:name];
[query getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) {
NSString *email = [object valueForKey:#"email"];
}
If you want to fetch the email of current user(Logged in user) then you can use this :
NSString *email =[[PFUser CurrentUser] [#"email"];