Validation for numbers (0-9) in textfield

Question

I am trying to validate textfield for numbers only.

I am using the following method:

if(isnumber(noOfPassengers.text.intValue))
{
    NSLog(@"value entered correctly.");
    return ;
}
else
NSLog(@"Error: Only numerica values are accepted");

isnumber() function is not working as expected. I would like to validate for numbers only. Got stuck here. Any other inbuilt function to check for numbers or even characters?

Does this work? If not, what happens that is not as expected? Please be specific in where you are having difficulty. — PengOne, Jan 11 '12 at 19:26
possible duplicate of [iPhone how to check that a string is numeric only](http://stackoverflow.com/questions/1320295/iphone-how-to-check-that-a-string-is-numeric-only) — PengOne, Jan 11 '12 at 19:33
Please could you give more information ie. what is wrong with your method that you used. Does the above method work as planned or is it just buggy code. — Keagan Ladds, Jan 11 '12 at 19:28

score 4 · Answer 1 · answered Jan 11 '12 at 19:49

You haven't posted any code for your function isnumber, so it's impossible to diagnose the problem there. However, writing the function from scratch, here is what I would do:

-(BOOL)isNumeric:(NSString*)inputString{
    NSCharacterSet *alphaNumbersSet = [NSCharacterSet decimalDigitCharacterSet];
    NSCharacterSet *stringSet = [NSCharacterSet characterSetWithCharactersInString:inputString];
    return [alphaNumbersSet isSupersetOfSet:stringSet];
}

Ben S · Answer 2 · 2012-01-11T19:35:36.980

3

The correct thing to do here is to implement the UITextFieldDelegate's textField:shouldChangeCharactersInRange:replacementString: to only accept numeric characters.

In the delegate method, return YES and strip any characters that aren't in the decimal character set.

edited Jan 11 '12 at 19:35

answered Jan 11 '12 at 19:28

Ben S

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The `isnumber()` function takes a C `char` and returns `1` if the char represents a decimal digit, otherwise it returns `0`. It can't do what you're asking for. – Ben S Jan 11 '12 at 19:54
I like this better. Better to fix it on the front end instead of letting the user enter something wrong and warning them. Using this alongside a numeric keyboard presentation sounds good to me. – LJ Wilson Jan 11 '12 at 20:37

score 1 · Accepted Answer · answered Jan 11 '12 at 19:38

Use NSScanner:

int iValue;

if (noOfPassengers.text.length > 0 && [[NSScanner scannerWithString:noOfPassengers.text] scanInt:&iValue]) {
    //do smomething with iValue (int value from noOfPassengers.text)
    NSLog(@"value entered correctly.");
    return ;
}
else
    NSLog(@"Error: Only numerica values are accepted");

score -2 · Answer 4 · answered Jan 11 '12 at 19:25

-2

for iOS, you should allow only numeric keyboard to appear instead. user will have no choice to input any other value except numbers..

answered Jan 11 '12 at 19:25

Saurabh Passolia

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score -2 · Answer 5 · answered Jan 11 '12 at 19:50

-2

Simple answer to your question is just show Numeric keyboard and check the value then. You don't have to implement UITextFieldDelegate's @Ben.s suggested.

answered Jan 11 '12 at 19:50

AAV

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Users can still paste non-numeric text or use an external keyboard. If the code assumes a numeric input, this could break the app. – Ben S Jan 11 '12 at 19:55

Validation for numbers (0-9) in textfield

5 Answers5