NSString 和 NSArray相互转化用componentsJoinedByString和componentsSeparatedByString

将array数组转换为string字符串

 NSString *tempString = [mutableArray componentsJoinedByString:@","];

将string字符串转换为array数组

 NSArray  *array = [str componentsSeparatedByString:@","]; // 意思是通过“,”来切割字符串

将字符串切割成数组

- (void)viewDidLoad

{

NSString *a = [[NSString alloc] initWithString : @"冬瓜，西瓜，火龙果，大头，小狗" ];

    NSArray *b = [a componentsSeparatedByString:@"，"];

     NSString *a3 = [b objectAtIndex:2];

     NSLog(@"\n  b的第三个东东是： %@", a3);

}

b的第三个东东是： 火龙果