UITextField restriction-iphone - iphone

Question

I'm having 4 textfields in my application
1.username
2.Email
3.Age
4.Password
User names are 3-25 characters and contain only the characters [a-z0-9]
Age must be between 1-100 inclusive.
Passwords are between 4-12 characters and use only the characters [a-zA-Z0-9]
how can i restrict the textfield with above requirements
please anyone help me out to do this..
Thank you for your effort and consideration.

Answer 1

You can use the methods in the UITextFieldDelegate protocol to validate your fields' content.
More concretely, either you use:
– textFieldShouldEndEditing:
- textFieldShouldReturn:
or you can use:
- textField:shouldChangeCharactersInRange:replacementString:
In the first case, you only validate when the user ends editing the text field; in the second case, you can do the validation at each keystroke.
In all of those methods, you receive an argument textField which you can access like this:
NSString* text = textField.text;
NSUInterger length = [text length];
if (length.....) {
// -- show alert or whatever
return NO;
}

Answer 2

You can validate numbers as the user type by implementing -[UITextField textField:shouldChangeCharactersInRange:replacementString:] method. Do note that this method is called before the change is made, so you need to construct the text that could be the result of the users actions yourself. For example:
-(BOOL)textField:(UITextField*)textField: shouldChangeCharactersInRange:(NSRange*)range
replacementString:(NSString*)string;
{
NSString* text = [textField.text stringByReplacingCharactersInRange:range
withString:string];
// text is now the potential string you should check against.
}
What you do from there is up to your own. Some examples could be:
// Too short?
if ([text length] < 4) ...
// Invalid character?
NSCharacterSet* invalidChars = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
if ([text rangeOfCharacterInSet:invalidChars].location != NSNotFound) ...
For more complex number validation I would use NSNumberFormatter, that has support for validating ranges and more.

Answer 3

You can use UITextFieldDelegate to get done what you want. Assign different values to textfield.tag for each field in - (void)viewDidLoad method and match those tag values to find the relevant field in the (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string.
#define USERNAME_FIELD_TAG 1
#define PASSWORD_FIELD_TAG 2
#define EMAIL_FIELD_TAG 3
#define AGE_FIELD_TAG 4
#pragma mark - UITextFieldDelegate
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
if (textField.tab == USERNAME_FIELD_TAG)
{
if([[NSPredicate predicateWithFormat:#"SELF MATCHES[cd] %#", #"[a-z0-9]{3,35}"] evaluateWithObject:string] == FALSE)
{
textField.text = [textField.text stringByReplacingOccurrencesOfString:string withString:#"" options:NSCaseInsensitiveSearch range:range];
[self selectTextForInput:textField atRange:range];
return NO;
}
}
else if (textField.tab == PASSWORD_FIELD_TAG)
{
if([[NSPredicate predicateWithFormat:#"SELF MATCHES[cd] %#", #"[a-zA-Z0-9]{4,12}"] evaluateWithObject:string] == FALSE)
{
textField.text = [textField.text stringByReplacingOccurrencesOfString:string withString:#"" options:NSCaseInsensitiveSearch range:range];
[self selectTextForInput:textField atRange:range];
return NO;
}
}
else if (textField.tab == EMAIL_FIELD_TAG)
{
if([[NSPredicate predicateWithFormat:#"SELF MATCHES[cd] %#", #"[A-Z0-9a-z._%+-]+#[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}"] evaluateWithObject:string] == FALSE)
{
textField.text = [textField.text stringByReplacingOccurrencesOfString:string withString:#"" options:NSCaseInsensitiveSearch range:range];
[self selectTextForInput:textField atRange:range];
return NO;
}
}
else if (textField.tab == AGE_FIELD_TAG)
{
if([[NSPredicate predicateWithFormat:#"SELF MATCHES[cd] %#", #"[1-100]"] evaluateWithObject:string] == FALSE)
{
textField.text = [textField.text stringByReplacingOccurrencesOfString:string withString:#"" options:NSCaseInsensitiveSearch range:range];
[self selectTextForInput:textField atRange:range];
return NO;
}
}
return YES;
}
// place the cursor at given possition
-(void)selectTextForInput:(UITextField *)input atRange:(NSRange)range {
UITextPosition *start = [input positionFromPosition:[input beginningOfDocument]
offset:range.location];
UITextPosition *end = [input positionFromPosition:start
offset:range.length];
[input setSelectedTextRange:[input textRangeFromPosition:start toPosition:end]];
}