Objective-C 中的 sizeof 运算符和三元运算符

Objective-C 语言还支持一些其他重要的运算符，包括sizeof 和?:。

运算符	描述	示例
sizeof()	返回变量的大小。	如果 a 是整数，sizeof(a) 将返回 4。
&	返回变量的地址。	&a; 将给出变量的实际地址。
*	指向变量的指针。	*a; 将指向一个变量。
? :	条件表达式	如果条件为真？则值为 X：否则值为 Y

示例

尝试以下示例以了解 Objective-C 编程语言中所有杂项运算符：

在线演示

#import <Foundation/Foundation.h>

int main() {
   int a = 4;
   short b;
   double c;
   int* ptr;

   /* example of sizeof operator */
   NSLog(@"Line 1 - Size of variable a = %d\n", sizeof(a) );
   NSLog(@"Line 2 - Size of variable b = %d\n", sizeof(b) );
   NSLog(@"Line 3 - Size of variable c= %d\n", sizeof(c) );

   /* example of & and * operators */
   ptr = &a;	/* 'ptr' now contains the address of 'a'*/
   NSLog(@"value of a is  %d\n", a);
   NSLog(@"*ptr is %d.\n", *ptr);

   /* example of ternary operator */
   a = 10;
   b = (a == 1) ? 20: 30;
   NSLog(@"Value of b is %d\n", b );

   b = (a == 10) ? 20: 30;
   NSLog(@"Value of b is %d\n", b );
}

编译并执行上述程序后，将产生以下结果：

2013-09-07 22:46:22.702 demo[24593] Line 1 - Size of variable a = 4
2013-09-07 22:46:22.703 demo[24593] Line 2 - Size of variable b = 2
2013-09-07 22:46:22.703 demo[24593] Line 3 - Size of variable c= 8
2013-09-07 22:46:22.703 demo[24593] value of a is  4
2013-09-07 22:46:22.703 demo[24593] *ptr is 4.
2013-09-07 22:46:22.703 demo[24593] Value of b is 30
2013-09-07 22:46:22.703 demo[24593] Value of b is 20

objective_c_operators.htm

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