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Objective-C關係運算子

2019-10-16 23:15:40

下表顯示了Objective-C語言支援的所有關係運算子。假設變數A=10，變數B=20，則 -

運算子 描述 範例
== 比較兩個運算元的值是否相等; 如果相等，則條件成立。 (A == B)結果為：false
!= 比較兩個運算元的值是否相等; 如果不相等，則條件成立。 (A != B)結果為：true
> 比較左運算元的值是否大於右運算元的值; 如果是，則條件成立。 (A > B)結果為：false
< 比較左運算元的值是否小於右運算元的值; 如果是，則條件成立。 (A < B)結果為：true
>= 比較左運算元的值是否大於等於右運算元的值; 如果是，則條件成立。 (A >= B)結果為：false
<= 比較左運算元的值是否小於等於右運算元的值; 如果是，則條件成立。 (A <= B)結果為：true

例子

嘗試以下範例來了解Objective-C程式設計語言中可用的所有關係運算子 -

 Live Demo
#import <Foundation/Foundation.h>

int main() {
   int a = 21;
   int b = 10;

   if( a == b ) {
      NSLog(@"Line 1 - a is equal to b\n" );
   } else {
      NSLog(@"Line 1 - a is not equal to b\n" );
   }

   if ( a < b ) {
      NSLog(@"Line 2 - a is less than b\n" );
   } else {
      NSLog(@"Line 2 - a is not less than b\n" );
   } 

   if ( a > b ) {
      NSLog(@"Line 3 - a is greater than b\n" );
   } else {
      NSLog(@"Line 3 - a is not greater than b\n" );
   }

   /* 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\n" );
   }

   if ( b >= a ) {
      NSLog(@"Line 5 - b is either greater than  or equal to b\n" );
   }
}

執行上面範例程式碼，得到以下結果：

2018-11-14 05:01:20.415 main[49282] Line 1 - a is not equal to b
2018-11-14 05:01:20.417 main[49282] Line 2 - a is not less than b
2018-11-14 05:01:20.417 main[49282] Line 3 - a is greater than b
2018-11-14 05:01:20.417 main[49282] Line 4 - a is either less than or equal to  b
2018-11-14 05:01:20.417 main[49282] Line 5 - b is either greater than  or equal to b