嵌套if语句（nested if statements）

在Objective-C编程中nest if-else语句总是合法的，这意味着你可以在另一个if或else if语句中使用if或else if语句。

语法 (Syntax)

nested if语句的语法如下 -

if( boolean_expression 1) {
   /* Executes when the boolean expression 1 is true */
   if(boolean_expression 2) {
      /* Executes when the boolean expression 2 is true */
   }
}

您可以使用与嵌套if语句类似的方式嵌套if else if...else 。

例子 (Example)

#import <Foundation/Foundation.h>
int main () {
   /* local variable definition */
   int a = 100;
   int b = 200;
   /* check the boolean condition */
   if( a == 100 ) {
      /* if condition is true then check the following */
      if( b == 200 ) {
         /* if condition is true then print the following */
         NSLog(@"Value of a is 100 and b is 200\n" );
      }
   }
   NSLog(@"Exact value of a is : %d\n", a );
   NSLog(@"Exact value of b is : %d\n", b );
   return 0;
}

编译并执行上述代码时，会产生以下结果 -

2013-09-07 22:08:19.984 demo[18141] Value of a is 100 and b is 200
2013-09-07 22:08:19.985 demo[18141] Exact value of a is : 100
2013-09-07 22:08:19.985 demo[18141] Exact value of b is : 200