NSMutableArray *array =@[@"111",@"4444",@"33333"].mutableCopy;
// 数组转字符串
NSString *str = [array componentsJoinedByString:@","];
NSLog(@"%@",str);
// 字符串转数组
NSArray * ar = [str componentsSeparatedByString:@","];
NSLog(@"%@",ar);