iPhone program crash on float to string conversion

I have an issue in getting a string that has been converted from a float to display in a label in a custom cell in a UITableView.

The program will crash if I try to assign the value of the float to the label. If I leave "strAIAreaIncrease = @"6.5%";" uncommented, the program works fine - but without the calculated value.

strAIAreaIncrease = [NSString stringWithFormat:@"%.2f",fltAreaIncrease];
strAIAreaIncrease = [strAIAreaIncrease stringByAppendingString:@"%"];
DebugLog(@"The value of float num is %.2f", fltAreaIncrease);
DebugL开发者_Python百科og(@"The value of the string is %@", strAIAreaIncrease);
// strAIAreaIncrease = @"6.5%"; 

The Debugger Console shows the following:

2010-11-14 19:52:38.122 Building Use[855:207]  The value of float num is 2.50
2010-11-14 19:52:38.123 Building Use[855:207]  The value of the string is 2.50%

I have used this format on other custom cell labels without issue. Anyone have any idea as to what is going on?

Thanks.

---

I think you should use NSMutableString instead:

e.g.

NSMutableString* straIAreaIncrease 
    = [NSMutableString stringWithFormat:@"%.2f", fltAreaIncreas];
[strAIAreaIncrease appendString:@"%%"];

---

OK, I have tried to implement NSMutabeString without success. It is obvious that I am missing a fundemental understanding of the MSMutableString.

I think that the way that I am creating it is part of the problem. I need to be able to pass the variable to several methods, so I am trying to create it in the header. It seems all of the examples I come across create the string within a method.

In my header I have:

NSMutableString *strAIAreaIncrease;

I think that this is a pert of the problem and I think that I need to assign it a value, but am not sure how. The Debugger Console gives the following:

2010-11-21 07:40:40.456 Building Use[1274:207] *** Terminating app due to uncaught exception
'NSInvalidArgumentException', reason: '+[NSMutableString string:]: unrecognized selector sent to class 0x2317c0'

Another question is this: If I am then using the MSMutableString value in an array, does the array have to be an MSMutable Array?

Thanks.

---

The problem is not in the header. It seems that you are using

strAIAreaIncrease = [NSMutableString string:@"someString"];

But there is no method "string:" in the Class NSMutableString. Try to use

strAIAreaIncrease = [NSMutableString stringWithString:@"someString"];

or

strAIAreaIncrease = [NSMutableString stringWithFormat:@"someString %d", someInteger];

About your second question: No you don't have to use a NSMutableArray, when dealing with NSMutableString. The "Mutable" in NSMutableArray means that you can add and remove objects from the array after it is generated.