#import <Foundation/Foundation.h>  #pragma mark - 创建可变字符串 void stringCreate(){     NSMutableString *str=[[NSMutableString alloc] initWithCapacity:10];//预分配是个空间,提高效率     //设置字符串的内容     [str setString:@"123"];     //连接字符串     [str appendFormat:@"age is %i and height is %.2f",27,175.5f];     [str appendString:@"添加结束"];     //字符串替换     NSRange range=[str rangeOfString:@"age"]; //找到当前字符串的位置     [str replaceCharactersInRange:range withString:@"年龄"];  //替换字符串     //插入字符串     [str insertString:@"我是插入的字符串" atIndex:2];     NSLog(@"可变字符串是:%@",str);     [str release];//释放对象      }  int main(int argc, const char * argv[]) {      @autoreleasepool {                  stringCreate();     }     return 0; }

结果：

2013-08-02 15:29:58.909 NSMutableString[1145:303] 可变字符串是:12我是插入的字符串3年龄 is 27 and height is 175.50添加结束