将数组拼接成字符串

//字符串转变为数组1

NSMutableString

• str=[[
  NSMutableString
  alloc]initWithFormat:@
  "1,1,1,1,1,1"
  ];

//字符串转变为数组2

NSMutableArray

• array=[
  NSMutableArray
  arrayWithArray:[str componentsSeparatedByString:@
  ","
  ]];

//替换数组中的某个值

[array replaceObjectAtIndex:4 withObject:@
"2"
];

//把数组转换成字符串

NSString
*ns=[array componentsJoinedByString:@
","
];