Textfield Input Validation in iPhone SDK - iphone

Question

I have to put validation on a UITextField for user input.
The user must input into the textfield a value
i.e. 70-80 or 85 mean num-num or num
Right now, I just allow to user to input only digits& - but drawback is that user can also input - number of times.
// My code is as follow
NSCharacterSet * set = [[NSCharacterSet characterSetWithCharactersInString:#"0123456789-"] invertedSet];
if (([txtMarks.text rangeOfCharacterFromSet:set].location != NSNotFound )||[txtMarks.text isEqualToString:#""] ) {
UIAlertView *alt=[[UIAlertView alloc]initWithTitle:#"Error" message:#"Invalid Input" delegate:nil cancelButtonTitle:#"Ok" otherButtonTitles:nil, nil];
[alt show];
[alt release];
}

Answer 1

Simply Try this,
int times = [[txtMarks.text componentsSeparatedByString:#"-"] count]-1;
if(times>1)
{
UIAlertView *alt=[[UIAlertView alloc]initWithTitle:#"Error" message:#"'-' used more than one" delegate:nil cancelButtonTitle:#"Ok" otherButtonTitles:nil, nil];
[alt show];
[alt release];
}
EDIT 1
Using NSPredicate we can do it. Try this,
NSString *regex = #"[0-9]+(-[0-9]+)?";
NSPredicate *testRegex = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", regex];
if([testRegex evaluateWithObject:textField.text])
NSLog(#"Match");
else
NSLog(#"Do not match");
Hope that can help.

Answer 2

Try this first find whether your string contains -
Here subtring is -
if ([txtMarks.text hasPrefix:#"-"]||[txtMarks.text hasSuffix:#"-"])
{
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:#"sorry " message:#"invalid inoput as it has - at start or end" delegate:nil cancelButtonTitle:#"OK" otherButtonTitles: nil];
[alert show];
[alert release];
}
else
{
NSRange textRange;
textRange =[string rangeOfString:substring];
if(textRange.location == NSNotFound)
{
//Does not contain the substring
NSlog(#" string contains only num")
}
else
{
int times = [[txtMarks.text componentsSeparatedByString:#"-"] count];
if(times==2)
{
Nslog(#"num-num input")
}
else
{
UIAlertView *alt=[[UIAlertView alloc]initWithTitle:#"Error" message:#"'-' used more than one" delegate:nil cancelButtonTitle:#"Ok" otherButtonTitles:nil, nil];
[alt show];
[alt release];
}
}
}

Answer 3

Try it using the following regular expression, It restricts user to enter more than one -.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];
NSString *expression = #"^([0-9]{1,}+)?(\\-([0-9]{1,})?)?$";
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:expression
options:NSRegularExpressionCaseInsensitive
error:&error];
NSUInteger numberOfMatches = [regex numberOfMatchesInString:newString
options:0
range:NSMakeRange(0, [newString length])];
if (numberOfMatches == 0)
{
return NO;
}
return YES;
}