Question

im learning cocos2d [open gl wrapper for objective C on iPhone], and now playing with sprites have found this in a example,

 enum {  
easySprite =   0x0000000a,
mediumSprite = 0x0000000b,
hardSprite =   0x0000000c,
backButton =   0x0000000d,
magneticSprite = 0x0000000e,
magneticSprite2 = 0x0000000f
};

…

 -(id) init
 {...
  /second sprite
    TSprite *med = [TSprite spriteWithFile:@"butonB.png"]; //blue
    [med SetCanTrack:YES];
    [self addChild: med z:1 tag:mediumSprite];
    med.position=ccp(299,230);
    [TSprite track:med];

so the variable defined in the enum is used in the tag name of the created sprite object,

but i don understand

1. why give values in hexa to the tags to use
2. the enum with out tags

as I knew this enum in obj C and C

     typedef enum {
     JPG,
     PNG,
      GIF,
     PVR
     } kImageType;

thanks!

Answer 1

Enums are automatically assigned values, incremented from 0 but you can assign your own values.

If you don’t specify any values they will be starting from 0 as in:

typedef enum {
 JPG,
 PNG,
 GIF,
 PVR
 } kImageType;

But you could assign them values:

typedef enum {
 JPG = 0,
 PNG = 1,
 GIF = 2,
 PVR = 3
 } kImageType;

or even

typedef enum {
 JPG = 100,
 PNG = 0x01,
 GIF = 100,
 PVR = 0xff
 } kImageType;

anything you want, repeating values are ok as well.

I’m not sure why they are given those specific values but they might have some meaning related to use.