Objective-C 關係運算符

下表列出了所有支持Objective-C語言的關係運算符。假設變量A=10和變量B=20，則：

運算符

描述

示例

==

檢查是否兩個操作數的值等於或不等於，如果是的話那麼條件爲真。

(A == B) is not true.

!=

檢查兩個操作數的值等於或不相等，如果值不相等，則條件爲真。

(A != B) is true.

>

檢查是否左操作數的值大於右操作數的值，如果是的話那麼條件爲真。

(A > B) is not true.

<

檢查是否左操作數的值小於右操作數的值，如果是的話那麼條件爲真。

(A < B) is true.

>=

檢查是否左操作數的值大於或等於右操作數的值，如果是的話那麼條件爲真。

(A >= B) is not true.

<=

檢查是否左操作數的值小於或等於右邊的操作數的值，如果是的話那麼條件爲真。

(A <= B) is true.

例子

嘗試下面的例子就明白了在Objective-C編程語言的所有關係運算符：

#import <Foundation/Foundation.h> main() { int a = 21; int b = 10; int c ; if( a == b ) { NSLog(@"Line 1 - a is equal to b
" ); } else { NSLog(@"Line 1 - a is not equal to b
" ); } if ( a < b ) { NSLog(@"Line 2 - a is less than b
" ); } else { NSLog(@"Line 2 - a is not less than b
" ); } if ( a > b ) { NSLog(@"Line 3 - a is greater than b
" ); } else { NSLog(@"Line 3 - a is not greater than b
" ); } /* Lets change value of a and b */ a = 5; b = 20; if ( a <= b ) { NSLog(@"Line 4 - a is either less than or equal to b
" ); } if ( b >= a ) { NSLog(@"Line 5 - b is either greater than or equal to b
" ); } }

當編譯和執行上述程序，它會產生以下結果：

2013-09-07 22:42:18.254 demo[9486] Line 1 - a is not equal to b
2013-09-07 22:42:18.254 demo[9486] Line 2 - a is not less than b
2013-09-07 22:42:18.254 demo[9486] Line 3 - a is greater than b
2013-09-07 22:42:18.254 demo[9486] Line 4 - a is either less than or equal to b
2013-09-07 22:42:18.254 demo[9486] Line 5 - b is either greater than or equal to b