BOOL类型的本质
typedef signed char BOOL;
BOOL类型的变量有2种取值：YES、NO
#define YES (BOOL)1
#define NO  (BOOL)0
BOOL的输出(当做整数来用)
NSLog(@"%d %d", YES, NO);

BOOL类型的本质
typedef signed char BOOL;
BOOL类型的变量有2种取值：YES、NO
#define YES (BOOL)1
#define NO  (BOOL)0
BOOL的输出(当做整数来用)
NSLog(@"%d %d", YES, NO);