Declare interface inside implementation file (Objective-C)

Question

In the last verson ox xCode (4.3) I've seen that prefdefined templates (such us Master/Detail template) in which the interface declaration is made in the .m file. For example, in the file MyFile.h there is:

@interface MyFile

@property (nonatomic, retain) NSString *someProp;

@end

And in the MyFile.m file there is:

@implementation MyFile

@interface MyFile {
    NSString * anotherProp;
}

- (id) init...

Why it's made on this way? Why the anotherProp isn't declared into the MyFile.h file?

Thanks in advance

That's not what it looks like, because that's invalid code. It's probably this: @interface MyFile () { NSString * anotherPropt } @end @implementation MyFile - (id) init {..., in which case see: stackoverflow.com/questions/9751057/… — jscs
– jscs, Commented May 18, 2012 at 6:47
You're right, I posted it from memory and I forgot the parenthesis — rai212
– rai212, Commented May 18, 2012 at 7:03

Abhishek Singh · Accepted Answer · 2012-05-18 07:00:44Z

5

Well its not declared this way but this way :-

@interface ClassName() {

    Declarations;

}

Methods;

@end

These are called class extension.They are similar to categories but can be declared only in implementation of the class not in any other class.The use of extensions is to redeclare property that is public or readwrite , also declare newer ones , if needed.They simply allow you to declare properties and variables in places other than @interface so the name extensios.

It was inrtoduced to tackle the problem with categories as they make the methods public and data hiding capability of classes is compensated but a class extension effectively extends the class’s primary interface which the declared methods have the same requirements as methods declared in the class’s oft public primary interface.

edited May 18, 2012 at 7:00

answered May 18, 2012 at 6:52

Abhishek Singh

6,1761 gold badge26 silver badges27 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

rai212 Over a year ago

You're right, I forgot the parenthesis. Thank you for your explanation, I understand it now

jscs Over a year ago

Categories can make non-public methods too (as far as any method is "non-public" in ObjC, anyways), as long as their declaration is hidden. The differences are that methods declared in extensions must be defined in the class's primary @implementation block, and that extensions can (as of a few compiler revisions ago) declare ivars.

SnakingPrabhu Over a year ago

@roronoa How to access interface class methods inside other class implementation? i try to declare that interface class name in other view class that class name not populated....

Collectives™ on Stack Overflow

Declare interface inside implementation file (Objective-C)

1 Answer 1

3 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Linked

Related