I want to have the user type in something. And I want to verify each character inputed. How could I do this? I want it to be in real time. So as its typed its being verified and color coded.
You could compare what I want to do to an programmers IDE how it checks the syntax as you type it.
Any help is appreciated!
Connect the UITextField delegate to the app delegate and do something like:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if([string isEqual:#"b"]) {
// User typed 'b'
// Insert string with specific color
// [...]
} else {
// User typed something else
// Insert string without specific color
textField.text = [textField.text stringByReplacingCharactersInRange:range withString:string];
}
return YES;
}
Related
I'm writing application in which I need to validate text entered by user to UITextField, char by char with some method.
The difficult thing is that client wants to do all the validation before user see character in the UITextField because there might be situation that his server application doesn't support '$' sign, so in my validation method I should replace it with 'USD' string - and he doesn't want user to see '$', just 'USD' immediately.
I know about events like UIControlEventEditingChanged etc., but still, I don't know 2 things:
how to access character typed by user before it's seen in UITextField and execute validation there
how to subtitute this character 'on the fly' and put it manually to UITextField (but I suppose I'll just append this to [[textField] text] NSString
Thank You in advance for any help :)
Implement the UITextFieldDelegate method textField:shouldChangeCharactersInRange:replacementString:, e.g.:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
BOOL validated = ...; //do your validation
return validated;
}
Similar to omz's answer but more complete code if you need:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSString *filtered;
filtered = [string stringByReplacingOccurrencesOfString:#"$" withString:#"USD"];
//optionally if you want to only have alphanumeric characters
//NSMutableCharacterSet *mcs1 = [[[NSCharacterSet letterCharacterSet] invertedSet] mutableCopy]; //only alphabet character
//[mcs1 removeCharactersInString:#"0123456789"];
//filtered = [[filtered componentsSeparatedByCharactersInSet:mcs1] componentsJoinedByString:#""];
//release mcs1;
return [string isEqualToString:filtered];
}
I am presenting the user with a field that displays the number keyboard and only want them to be able to enter numbers with decimal it should be only one. After decimal it is should be at least 2 digits will be there. There should be at least one digit before the decimal. Then the input can`t be 0 or 0.00. Suppose if user enter the number 123456 it is accepted then 123.56 it also accepted how can I do this one please help me.
you can make a regex for this requirement like:-
NSString *numberRegEx = #"[0-9]+[.]{0,1}+[0-9]{0,2}";
NSPredicate *numberTest = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", numberRegEx];
//Valid email address
if ([numberTest evaluateWithObject:textField.text] == YES)
{
NSLog(#"correct value");
}
else
{
NSLog(#"incorrect value");
}
First, add a target for UIControlEventEditingChanged of your text field:
[textField addTarget:self action:#selector(onEdit:) forControlEvents:UIControlEventEditingChanged];
add a BOOL property to your class:
#property(nonatomic, assign) BOOL formatting;
then create an onEdit: method like this:
-(void)onEdit:(UITextField*)field {
//if you have more than one text field you can check for the one you need to format
if(!self.formatting) {
NSString* formattedText = ...//get the formatted text according to your rules
self.formatting = YES;//infinite loop prevention
field.text = formattedText;
self.formatting = NO;
}
}
You can impose all your conditions in the -(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string method. Here, textField.text will be the most recent text that the user has entered. You can parse it and see whether any of your conditions are not being met. Return NO in that case.
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
if(allConditionsMet)
return YES;
return NO;
}
HTH,
Akshay
I have an UITextField and I would like that for every tap on a character, the first character is deleted. So that I just have one character in my textField every time. Moreover I would like it to display every tap in the console log.
How can I do this?
You need to implement shouldChangeCharactersInRange method in your text field delegate:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:
(NSRange)range replacementString:(NSString *)string{
textField.text = #"";
return YES;
}
You may need to check for range and string values to cover all possible cases (like copy/paste actions). This code just sets the text field's value to the last typed character.
UITextField inherits from UIControl, so you can use the target-action mechanism that is part of the UIControl class:
[textField addTarget:self action:#selector(updateTextField) forControlEvents:UIControlEventValueChanged];
In the action method, you can replace the UITextField's text with only the last character and log that character in the console. Note that since changing the UITextField's text will again result in the "updateTextField" message being sent a second time to the target, you will need some kind of mechanism for determining whether to update or not:
- (void)updateTextField {
if(updateTextField == YES) {
updateTextField = NO;
NSString *lastChar = [textField.text substringFromIndex:[textField.text length]];
[textField setText:lastChar];
NSLog(#"%#", lastChar);
} else {
updateTextField = YES;
}
}
Or something like that anyway...
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (textField.text.length > 8) {
return NO;
}
return YES;
}
i want to let the user type in the name of a new file, so there are certain characters i want to prevent entry on. is there a special keyboard i can use or can i disable certain keys on the iphones keyboard.
is the answer to just run a regular expression on the input text and tell the user the filename is invalid (if so what would that regular expression be?)
ANSWER: (or what i ended up doing)
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
BOOL valid;
//if the user has put in a space at the beginning
if ([string isEqualToString:#" "]){
if (range.location == 0){
valid = NO;
}
else{
valid = YES;
}
}
//otherwise test for alpha numeric
else{
NSCharacterSet *alphaSet = [NSCharacterSet alphanumericCharacterSet];
valid = [[string stringByTrimmingCharactersInSet:alphaSet] isEqualToString:#""];
}
//print the warning label
if (valid == NO){
[errorLabel setText:#"Invalid input"];
}
else{
[errorLabel setText:nil];
}
return valid;
}
You can implement the delegate method
For UITextField,
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string; // return NO to not change text
For UITextview
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text;
and decide weather to append the entered characters or not.
You can implement the UITextFieldDelegate protocol and use textField:shouldChangeCharactersInRange:replacementString: to watch the text entry and prevent unwanted characters by returning NO.
I have a UITextField in my application. I'd like to restrict the set of characters that can be can be entered into the field to a set that I have defined. I could filter the characters entered into the field when the text is committed using the UITextFieldDelegate method:
- (BOOL)textFieldShouldReturn:(UITextField*)textField
However, this gives the user a false impression as although restricted characters are removed from the final value, they were still visibly entered into the text field before pressing Return/Done/etc. What is the best approach that would prevent restricted characters appearing in the text field as they are selected on the keyboard?
Note: I am operating under the assumption that I have little control over which keys are provided by the iPhone keyboard(s). I am aware that I can switch between various keyboard implementations but am under the impression that I can't disable specific keys. This assumption may be incorrect.
I did as marcc suggested and it worked well. Sample implementation follows.
Note: Variable names were selected for brevity and do not reflect my coding standards:
...
myCharSet = [NSCharacterSet characterSetWithCharactersInString:#"xyzXYZ"];
...
}
- (BOOL) textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)textEntered {
for (int i = 0; i < [textEntered length]; i++) {
unichar c = [textEntered characterAtIndex:i];
if (![myCharSet characterIsMember:c]) {
return NO;
}
}
return YES;
}
Look at textField:shouldChangeCharactersInRange
This method is called by the UITextFieldDelegate whenever new characters are typed or existing characters are deleted from the text field. You could return NO to not allow the change.
Here is one of the cleanest approaches to restricting characters entered in a UITextField. This approach allows the use of multiple predefined NSCharacterSets.
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
[allowedCharacters formUnionWithCharacterSet:[NSCharacterSet whitespaceCharacterSet]];
[allowedCharacters formUnionWithCharacterSet:[NSCharacterSet symbolCharacterSet]];
if([string rangeOfCharacterFromSet:allowedCharacters.invertedSet].location == NSNotFound){
return YES;
}
return NO;
}
Look at the UITextViewDelegate method - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string.
It's exactly what you need.
This is what I use to restrict the user to uppercase A-Z. Adjust the regex variable according to taste:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString* regex = #"[^A-Z]";
return ([string rangeOfString: regex
options:NSRegularExpressionSearch].location == NSNotFound);
};
How about this?
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString* regex = #"[^a-z]";
return ([[string lowercaseString] rangeOfString: regex
options:NSRegularExpressionSearch].location == NSNotFound);
};
Note:
I am making all characters to lower case [string lowercaseString] so that you don't need to write in regex for captial/small letters.
You could loop and keep checking if the UITextField.text property has changed once the DidBeginEditing method gets called. If it has, check the text and remove an bad characters.