Default Cocoa Application ViewController.m issue?

Question

Newbie question follows...

I am learning Objective C based OS X Cocoa app development. Most of the books and videos I have are for iOS, so I am converting some simple iOS code examples to OS X.

When I create a new OS X "Cocoa Application" project, with the "use Storyboards" box checked, the default ViewController.m in my newly created project does NOT have an @interface section. Is this expected?

A reply to my recent question Cocoa ViewController.m vs. Cocoa Touch ViewController.m indicates that another user's default ViewController.m DOES have an @interface section.

Currently, I am manually typing the @interface section for IBOutlets. Is that what others are doing? Or do I have some configuration issue?

I am using Xcode 6.3.2 on Yosemite.

Here is my default ViewController.m

//
//  ViewController.m
//  testME
//
//  Created by ME on 6/19/15.
//  Copyright (c) 2015 ME. All rights reserved.
//

#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // Do any additional setup after loading the view.
}

- (void)setRepresentedObject:(id)representedObject {
    [super setRepresentedObject:representedObject];

    // Update the view, if already loaded.
}

@end

LOP_Luke LOP_Luke · Accepted Answer · 2015-06-19T19:46:35

Typically the interface for a class (ViewController in your case) is in the header file (.h).

However some developers use the convention of putting a class extension at the top of implementation files as a way of "faking" private methods (which Objective C doesn't have.)

So you could see this in a .m file:

//The parenthesis here indicate a class extension.
@interface ViewController ()

//Only the ViewController class sees this method.
-(void) method;

@end

@implementation ViewController

-(void) method{
    //Do stuff here 
}

@end

This is not specific to iOS or MacOS but rather Objective C. You can see more about Objective C class extensions here.

The default Xcode project does not add a class extension for the created ViewController class. However if you create a new NSViewController subclass (by going to File->New->File->Cocoa Class, then create a class that is a subclass of NSViewController, you will notice the new NSViewController subclass will have a class extension generated at the top of the implementation file. This however is not required or necessary, just used as a way of defining the closest thing Objective C allows to a private interface.

You can also check out this answer for more details about implementing psuedo-private methods.

Default Cocoa Application ViewController.m issue?

1 Answers