| Name | Typedef | Header | True Value | False Value |
|---|---|---|---|---|
| BOOL | signed char | objc.h | YES | NO |
| bool | _Bool (int) | stdbool.h | true | false |
| Boolean | unsigned char | MacTypes.h | TRUE | FALSE |
| NSNumber | __NSCFBoolean | Foundation.h | @(YES) | @(NO) |
| CFBooleanRef | struct | CoreFoundation.h | kCFBooleanTrue | kCFBooleanFalse |
注意：
返回值不一样，所以判断的时候：
//这样写
if ([a isEqual:b] )
if ([a isEqual:b] == YES) //不能这样写