如何在Objective-C中定义和使用ENUM？

Question

I declared an enum in my implementation file as shown below, and declared a variable of that type in my interface as PlayerState thePlayerState; and used the variable in my methods. But I am getting errors stating that it is undeclared. How do I correctly declare and use a variable of type PlayerState in my methods?:

In the .m file

@implementation View1Controller

    typedef enum playerStateTypes
        {
            PLAYER_OFF,
            PLAYER_PLAYING,
            PLAYER_PAUSED
        } PlayerState;

in the .h file:

@interface View1Controller : UIViewController {

    PlayerState thePlayerState;

in some method in .m file:

-(void)doSomethin{

thePlayerState = PLAYER_OFF;

}

Answer 1

Apple provides a macro to help provide better code compatibility, including Swift. Using the macro looks like this.

typedef NS_ENUM(NSInteger, PlayerStateType) {
  PlayerStateOff,
  PlayerStatePlaying,
  PlayerStatePaused
};

Documented here

Answer 2

Your typedef needs to be in the header file (or some other file that's #import ed into your header), because otherwise the compiler won't know what size to make the PlayerState ivar. Other than that, it looks ok to me.

Answer 3

In the .h:

typedef enum {
    PlayerStateOff,
    PlayerStatePlaying,
    PlayerStatePaused
} PlayerState;

Answer 4

With current projects you may want to use the NS_ENUM() or NS_OPTIONS() macros.

typedef NS_ENUM(NSUInteger, PlayerState) {
        PLAYER_OFF,
        PLAYER_PLAYING,
        PLAYER_PAUSED
    };

Answer 5

This is how Apple does it for classes like NSString:

In the header file:

enum {
    PlayerStateOff,
    PlayerStatePlaying,
    PlayerStatePaused
};

typedef NSInteger PlayerState;

Refer to Coding Guidelines at http://developer.apple.com/

Answer 6

I recommend using NS_OPTIONS or NS_ENUM. You can read more about it here: http://nshipster.com/ns_enum-ns_options/

Here's an example from my own code using NS_OPTIONS, I have an utility that sets a sublayer (CALayer) on a UIView's layer to create a border.

The h. file:

typedef NS_OPTIONS(NSUInteger, BSTCMBorder) {
    BSTCMBOrderNoBorder     = 0,
    BSTCMBorderTop          = 1 << 0,
    BSTCMBorderRight        = 1 << 1,
    BSTCMBorderBottom       = 1 << 2,
    BSTCMBOrderLeft         = 1 << 3
};

@interface BSTCMBorderUtility : NSObject

+ (void)setBorderOnView:(UIView *)view
                 border:(BSTCMBorder)border
                  width:(CGFloat)width
                  color:(UIColor *)color;

@end

The .m file:

@implementation BSTCMBorderUtility

+ (void)setBorderOnView:(UIView *)view
                 border:(BSTCMBorder)border
                  width:(CGFloat)width
                  color:(UIColor *)color
{

    // Make a left border on the view
    if (border & BSTCMBOrderLeft) {

    }

    // Make a right border on the view
    if (border & BSTCMBorderRight) {

    }

    // Etc

}

@end