Objective-c里各种布尔类型什么区别

Question

boolean_t t;
Boolean tt;
BOOL ttt;
bool tttt;

这四种布尔类型有什么区别？
我看很多框架里的方法都用 BOOL 为什么？

Answer 1

bool 是int
BOOL 是char

bool b1 当b1>0 就＝YES
BOOL b2 当b2=1 才＝YES

所以框架都用BOOL

Boolean mac os上有历史意义的类型

Boolean types and values
    
        Boolean         Mac OS historic type, sizeof(Boolean)==1
        bool            Defined in stdbool.h, ISO C/C++ standard type
        false           Now defined in stdbool.h
        true            Now defined in stdbool.h

boolean_t i386

/*
 *	File:	boolean.h
 *
 *	Boolean type, for I386.
 */

#ifndef	_MACH_I386_BOOLEAN_H_
#define _MACH_I386_BOOLEAN_H_

#if defined(__x86_64__) && !defined(KERNEL)
typedef unsigned int	boolean_t;
#else
typedef int		boolean_t;
#endif

#endif	/* _MACH_I386_BOOLEAN_H_ */

Answer 2

boolean_t t1 = 1;//int type
Boolean t2 = 1; //unsigned char type
BOOL t3 = 4;//YES or NO
bool t4 = 1;//true or false

NSAssert(t1, @"boolean_t t1 is NO");//通过测试
NSAssert(t2, @"boolean_t t2 is NO");//通过测试
NSAssert(t3, @"boolean_t t3 is NO");//通过测试
NSAssert(t4, @"boolean_t t4 is NO");//通过测试

Answer 3

补充一下
typedef signed char BOOL;
// BOOL is explicitly signed so @encode(BOOL) == "c" rather than "C"
// even if -funsigned-char is used.

• define OBJC_BOOL_DEFINED

• define YES (BOOL)1
• define NO (BOOL)0