Enumeration in Objective C

Enum (enumerated type) is an user-defined type that is used in Objective-C to represent the data that can be stored in one of several predefined values (all of them are int).

Let’s imagine you have to implement a simple UIView that has three different visual modes: default (grey), green and red. Each mode is represented to user by three different pictures: my_mode_grey.png, my_mode_green.png and my_mode_red.png. All of three final views would have some common behavior. 

To understand it , lets take an example:

1) First create an enum

enum myMode {

         

         myViewModeDefault,  //== 0(by default)

         myViewModeGreen,   //  == 1 (incremented by one from previous)

         myViewModeBlue    // ==2 

};

It means that every “mode” is simply described by the unique int value (unique inside current enum). Each next enum mode is incremented by 1 by default. You can also set the enum mode values by yourself (if you really need it):

enum myMode {

         

         myViewModeDefault = 5,  //== 5 (redefined)

         myViewModeGreen,   //  == 6 (incremented by one from previous)

         myViewModeBlue  = 9   // ==2 

};

2) Now lets create a class:

#import <UIKit/UIKit.h>

@interface MyViews:UIView{

    enum myMode mode ;

}

-(id)initWithMode:(enum myMode)amode;

@end

3) implement our custom initializer:

@implementation MyViews

-(id)initWithMode:(enum myMode)amode{

      

             self = [super init];

            

             if(self){

                   mode = amode;

             

       //to store different images

      NSString  *imageName;

    

         switch(amode){

             

       case myViewModeDefault:

                               imageName = @"tom.png"

                                break; 

       case myViewModeDefault:

                               imageName = @"jery.png"

                                break; 

     case myViewModeDefault:

                               imageName = @"draculla.png"

                                break; 

     default:

                  imageName = @"sorry.png"

                                break; 

}

      UIImageView *imageView = [UIImageView alloc]initWithImage:[UIImage imageNamed: imageName]];

     [self addSubview:imageView];

}

return self;

}

@end

Thats it, how easy it is.