在Objective-C编程嵌套if-else语句，它始终是合法，这意味着你可以使用一个或else if语句if或else if语句放在另一个里面。

语法：

嵌套的if语句语法如下：

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

你可以嵌套else if...else其他类似的方法在已经嵌套 if语句。 

例子：

#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
" );
       }
   }
   NSLog(@"Exact value of a is : %d
", a );
   NSLog(@"Exact value of b is : %d
", b );
 
   return 0;
}

让我们编译和运行上面的程序，这将产生以下结果：

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