Question

I am trying to make this program so that the only time that there is a decimal is when the decimal is .5. I have been trying to use [string substringToIndex:[string length] - 2] but it does nothing. Is is because it cannot append the float?

float inchesInField = [sizeField.text floatValue];
float shoeSize = inchesInField * 3 - 22;
NSMutableString *appendedShoeSize = [[NSMutableString alloc]
                                            initWithFormat:@"%.1f", shoeSize];

if ([appendedShoeSize hasSuffix:@".3"] || [appendedShoeSize hasSuffix:@".5"] ||
    [appendedShoeSize hasSuffix:@".4"] || [appendedShoeSize hasSuffix:@".6"])
{
    [appendedShoeSize substringToIndex:[appendedShoeSize length] - 2];
    [appendedShoeSize appendString:@" ½"];
} 

if ([appendedShoeSize hasSuffix:@".0"] || [appendedShoeSize hasSuffix:@".1"] ||
    [appendedShoeSize hasSuffix:@".2"])
{
    [appendedShoeSize substringToIndex:[appendedShoeSize length] - 2];
}

Answer 1

it is because substringToIndex: method of NSString returns the new string, it doesn’t modify the original string. appendString: is fine, but substringToIndex: is a method of NSString so it will not edit the original string.

This should do it:

float inchesInField = [sizeField.text floatValue];
float shoeSize = inchesInField * 3 - 22;
NSMutableString *appendedShoeSize = [[NSMutableString alloc] initWithFormat:@"%.1f", shoeSize];

if ([appendedShoeSize hasSuffix:@".3"] || [appendedShoeSize hasSuffix:@".5"] || [appendedShoeSize hasSuffix:@".4"] || [appendedShoeSize hasSuffix:@".6"]) {

    appendedShoeSize = [[appendedShoeSize substringToIndex:[appendedShoeSize length] - 2] mutableCopy];
    [appendedShoeSize appendString:@" ½"];
} 

if ([appendedShoeSize hasSuffix:@".0"] || [appendedShoeSize hasSuffix:@".1"] || [appendedShoeSize hasSuffix:@".2"]) {

    appendedShoeSize = [[appendedShoeSize substringToIndex:[appendedShoeSize length] - 2] mutableCopy];
}