簡單枚舉類型

enum EOCConnectionState {
    EOCConnectionStateDisconnected,
    EOCConnectionStateConnecting,
    EOCConnectionStateConnected,
}
typedef enum EOCConnectionState EOCConnectionState;

這樣就可以簡寫的EOCConnectionState來代替完整的enum EOCConnectionState。

指定底層數(shù)據(jù)類型

enum EOCConnectionState : NSInteger {/* ... */}

或者向前聲明：

enum EOCConnectionState : NSInteger;

彼此組合的枚舉

各選項之間可以通過”按位或操作符”。

enum UIViewAutoresizing {
    UIViewAutoresizingNone = 0,
    UIViewAutoresizingFlexibleLeftMargin = 1 << 0,
    UIViewAutoresizingFlexibleWidth = 1 << 1,
    UIViewAutoresizingFlexibleRightMargin = 1 << 2,
    UIViewAutoresizingFlexibleTopMargin = 1 << 3,
    ...
}

Foundation框架輔助宏

這些宏具有向后兼容能力。

typedef NS_ENUM(NSUInteger, EOCConnectionState) {
    EOConnectionStateDisconnected,
    ...
}

typedef NS_OPTIONS(NSUInteger, EOCPermittedDirection) {
    EOCPermittedDirectionUp = 1 << 0,
    ...
}

用枚舉定義定義狀態(tài)機，最好不要有default分支。

switch(_currentState) {
    case EOCConnectionStateDisconnected:
        break;
    case EOCConnectionStateConnecting:
        break;
    case EOCConnectionStateConnected:
        break;
}