error : 'Attempt to mutate immutable object with appendString:' --

I am getting an error 'Attempt to mutate immutable object with appendString:'

and my code is

NSMutableString *resultString= [[NSMutableString alloc]init];


for (NSMutableString *s in self.ArrayValue)
{
    [resultString appendString:s];
    NSLog(resultString);

}  

Arra开发者_运维问答yValue is NSMutableArray.

I am not able to understand where is the problem

thank you in advance

As posted, the code you have will not give you the error you describe. Probably, somewhere between allocating resultString and the for loop, you are overwriting it with a normal NSSring.

Just do have like this:

It works for me...

    NSMutableString *resultString= [[NSMutableString alloc]init];
NSMutableArray *ArrayValue=[[NSMutableArray alloc]init];
[ArrayValue addObject:@"One"];
[ArrayValue addObject:@"Two"];
[ArrayValue addObject:@"Three"];

for (NSMutableString *s in ArrayValue)
{
    [resultString appendString:s];
    NSLog(@"%@",resultString);------->You should use %@ to print the string otherwise will show your warning.

}  

O/P on Console:

2011-03-08 19:13:02.243 iPadMables[4557:207] One

2011-03-08 19:13:06.224 iPadMables[4557:207] OneTwo

2011-03-08 19:13:09.388 iPadMables[4557:207] OneTwoThree

    ArrayValue = [NSMutableArray arrayWithObjects:@"b",@"o",@"n",nil];
NSMutableString *resultString= [[NSMutableString alloc]init];

for (NSMutableString *s in self.ArrayValue)
{
    [resultString appendString:s];
    NSLog(resultString);

}  

works for me..