Programmatical segue to new viewcontroller - ios

Question

In an if/else function depending on the conditions that're met I want to show some string as result to the user. I'm trying to do this by changing to a new viewController programatically. I have created a method 'showresult' that will be taking one variable 'result' as argument and then changing viewController and showing the content of 'result' on there.
For changing the viewController I now have:
Defined in .h as:
Then I'm trying to call this getData method in an if/else function:
Here I get 'no visible #interface for 'NSString' declares the selector 'getData'
I assume the error lies in my definition of the method, I just can't see why
--UPDATED Part--
I have now reached a point where the following way of changin viewController works for me:
[self performSegueWithIdentifier:#"gotoresult" sender:self];
Now I just need the last part, which is to pass on a variable to the new viewController. I have found other threads about passing something on, but just didn't understand how to apply this.
One suggestion I found was this one, but prepareforSegue isn't recognized in my Xcode
-(void)prepareforSegue:(UIStoryboardSegue *)segue sender:(id)sender{
GTImageView * viewController = segue.destinationViewController;
viewController.someData = 99;
}
I just need to be able to show some string on to that new viewController

Answer 1

The compiler is not complaining about self because the identifier is unknown but because the way you declare your method is wrong. In Objective-C you define methods like this:
- (returnType)doSomethingWithTheFirstParameter:(param1Type)param1 secondParameter:(param2Type)param2 {
// body
}
The name of your method would be -doSomethingWithFirstParameter:secondParamter:.
In the same manner you can add as many parameters as you like. So in your case the correct method definition would be:
- (NSString *)showResult:(NSString *)result {
// body
}
As this is very basic stuff I suggest you first read an introduction to Objective-C or do a tutorial in order to get familiar with the syntax, e.g. Programming with Objective-C.
Question has been edited. Answer to your new question:
The compiler tells you what's wrong with that code: In your if-branch you call the message getData on the object result which seems to be of class NSString. But you added the getData method to your view controller class. So when you want to call that method from inside the view controller you need to use
[self getData:result];
instead.
Furthermore you should not return 0 for a method of return type NSString. If you do not want the method to return anything change the method definition to:
- (void)showResult:(NSString *)result {
// body
}
and remove the line
return 0;
or return some NSString object.
Note: Please do not include screenshots of your code but copy the code and paste the text to your post instead. Besides other advantages you give other users the option to copy your code and try it out.