Objective-C语言的编程语言允许使用一个循环的另一循环内。下面的部分显示了几个例子来说明这个概念。
嵌套的for循环语句在C的语法如下：
for ( init; condition; increment ) { for ( init; condition; increment ) { statement(s); } statement(s); }
nested while loop 语句的语法在Objective-C编程语言的语句如下：
while(condition) { while(condition) { statement(s); } statement(s); }
嵌套 nested do...while loop 语句语法在Objective-C编程语言的语句如下：
do { statement(s); do { statement(s); }while( condition ); }while( condition );
循环嵌套最后需要说明的是，你可以把任何类型的循环内的任何其他类型的循环。例如，一个for循环，可以在while循环或反之亦然。
下面的程序使用嵌套的for循环找出2〜100中的素数
#import <Foundation/Foundation.h> int main () { /* local variable definition */ int i, j; for(i=2; i<100; i++) { for(j=2; j <= (i/j); j++) if(!(i%j)) break; // if factor found, not prime if(j > (i/j)) NSLog(@"%d is prime ", i); } return 0; }
上面的代码编译和执行时，它会产生以下结果：
2013-09-07 22:40:01.004 demo[1027] 2 is prime 2013-09-07 22:40:01.005 demo[1027] 3 is prime 2013-09-07 22:40:01.005 demo[1027] 5 is prime 2013-09-07 22:40:01.005 demo[1027] 7 is prime 2013-09-07 22:40:01.005 demo[1027] 11 is prime 2013-09-07 22:40:01.005 demo[1027] 13 is prime 2013-09-07 22:40:01.005 demo[1027] 17 is prime 2013-09-07 22:40:01.005 demo[1027] 19 is prime 2013-09-07 22:40:01.005 demo[1027] 23 is prime 2013-09-07 22:40:01.005 demo[1027] 29 is prime 2013-09-07 22:40:01.005 demo[1027] 31 is prime 2013-09-07 22:40:01.005 demo[1027] 37 is prime 2013-09-07 22:40:01.005 demo[1027] 41 is prime 2013-09-07 22:40:01.005 demo[1027] 43 is prime 2013-09-07 22:40:01.005 demo[1027] 47 is prime 2013-09-07 22:40:01.005 demo[1027] 53 is prime 2013-09-07 22:40:01.005 demo[1027] 59 is prime 2013-09-07 22:40:01.005 demo[1027] 61 is prime 2013-09-07 22:40:01.005 demo[1027] 67 is prime 2013-09-07 22:40:01.005 demo[1027] 71 is prime 2013-09-07 22:40:01.005 demo[1027] 73 is prime 2013-09-07 22:40:01.005 demo[1027] 79 is prime 2013-09-07 22:40:01.005 demo[1027] 83 is prime 2013-09-07 22:40:01.005 demo[1027] 89 is prime 2013-09-07 22:40:01.005 demo[1027] 97 is prime
