java与c语言中的bool类型有true和false两种两个值，bool是用来存储真／假值的类型。
1.Object-C也提供了一个类似的BOOL类型，它又YES和NO两个值。
2.BOOL和bool在同一个程序中可以共同存在，但是如果是Cocoa代码则只能用BOOL。
1.BOOL
它是对带符号的字符类型的类型定义，用8位的存储空间，通过宏定义
#define YES = 1
#define NO = 0
如果将大于8位的整型值赋值给BOOL类型的变量，一定要小心，它只会去后8位即低位的一个字节
如8960十六进制为0x2300，则转换为BOOL值为0认做是NO值。
//
// main.m
// Hello Project-c
//
// Created by Bin Wang on 2018/6/4.
// Copyright © 2018年 Isan. All rights reserved.
//
#import <Foundation/Foundation.h>
BOOL areIntsDifferent(int var1,int var2){
if(var1 == var2){
return NO;
}else{
return YES;
}
}
//返回值是指向NSString的指针，用%@来输出
NSString *boolString(BOOL yesNo){
if(yesNo == NO){
return (@"NO");
}else{
return (@"YES");
}
}
int main(int argc, const char * argv[]) {
@autoreleasepool {
// insert code here...
NSLog(@"Hello, World!");
}
NSLog(@"Hello,Objective-C !");
BOOL areTheyDifferent;
areTheyDifferent = areIntsDifferent(10, 24);
NSLog(@ "are %d and %d different? %@",10,24,boolString(areTheyDifferent));
areTheyDifferent = areIntsDifferent(15, 15);
NSLog(@ "are %d and %d different? %@",15,15,boolString(areTheyDifferent));
return 0;
}
运行结果：
2018-06-20 01:01:55.945924+0800 Hello Project-c[843:293486] Hello, World!
2018-06-20 01:01:55.946146+0800 Hello Project-c[843:293486] Hello,Objective-C !
2018-06-20 01:01:55.946199+0800 Hello Project-c[843:293486] are 10 and 24 different? YES
2018-06-20 01:01:55.946223+0800 Hello Project-c[843:293486] are 15 and 15 different? NO
Program ended with exit code: 0
