stringByReplacingCharactersInRange don't replace It's Append ! - iphone

Question

I Spent 5 hours try to figure a way for that..i'm trying to do a hangman app for iphone and the method below is the method that should be called when the player chooses a character and it match the chosen word..
-(void)replaceTheHiddenTextWithNewText:(NSString*)character{
NSString *fullTextField = fullText.text;
int textCount = [hiddenText.text length];
NSString *theRiddle;
for (int i = textCount-1 ; i>=0; i--) {
NSString *hiddenTextField = [[NSMutableString alloc] initWithString:hiddenText.text];
NSString *aChar=[fullTextField substringWithRange:NSMakeRange(i/3,1)];
if ([aChar isEqualToString:#" "]) {
theRiddle= [hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:#" "];
}else if ([aChar isEqualToString:character]) {
theRiddle =[hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:aChar];
}else{
theRiddle = [hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:#"_"];
}
hiddenTextField = theRiddle;
}
hiddenText.text=theRiddle;
}
the problem is stringByReplacingCharactersInRange doesn't replace the character, it appends it to the underscore what am I doing wrong here?
Best Regards,
M Hegab

Answer 1

Just played around with your code. It does not work, but stringByReplacingCharactersInRange is not your problem.
Your game logic doesn't work like it should. Get a pen and a sheet of paper and "manually" loop through your for loop to see that this must be wrong.
Next time, if you've stared at code for half an hour, take a pen. This will save you at least 4 hours :-)
There are some issues with your code. Assume Kartoffelkäfer is the word you are looking for, and the user enters the letter f.
for (int i = textCount-1 ; i>=0; i--) {
NSString *hiddenTextField = [[NSMutableString alloc] initWithString:hiddenText.text];
// you are creating this string in every loop from the text of a (I guess) UITextField.
// I don't know what the content of this text is but I guess it is suppossed to be `______________`
// in every loop you replace the word where you replaced the _ with the correct letter with the string from the textfield.
// Btw, you are leaking this string.
NSString *aChar=[fullTextField substringWithRange:NSMakeRange(i/3,1)];
// Kartoffelkäfer has 14 chars so i is 13. And 13/3 is 4. And the character at index 4 is o
// In the next loop i is 12. And 12/3 is 4, too.
// next three loops will give you index 3. Then you get three times index 2, and so one.
// you never reach the letter f, anyway.
if ([aChar isEqualToString:#" "]) {
theRiddle= [hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:#" "];
}else if ([aChar isEqualToString:character]) {
theRiddle =[hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:aChar];
}else{
theRiddle = [hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:#"_"];
// You should not replace a unmatched character with a _ . Because already matched letters would be overwritten.
}
hiddenTextField = theRiddle;
}
I assumed that the content of hiddenText.text is #"______"
and the content of fullText.text is #"Kartoffelkäfer". So hiddentext is the exact length as the fullText.
What I had to change to get this to work:
NSString *theRiddle;
NSString *hiddenTextField = [[[NSMutableString alloc] initWithString:hiddenText.text] autorelease];
for (int i = textCount-1 ; i>=0; i--) {
NSString *aChar=[fullTextField substringWithRange:NSMakeRange(i,1)];
if ([aChar isEqualToString:#" "]) {
theRiddle= [hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:#" "];
}else if ([aChar isEqualToString:character]) {
theRiddle =[hiddenTextField stringByReplacingCharactersInRange:NSMakeRange(i, 1) withString:aChar];
}
else {
theRiddle = hiddenTextField;
}
hiddenTextField = theRiddle;
}
hiddenText.text=theRiddle;
Far away from good code, but I tried to change your code as little as possible.