Question

I want to group the numbers entered into my amount field, using “.” as the grouping seperator, like 100.000

I implemented shouldChangeCharactersInRange method of my view controller so that only numbers and one comma is allowed for the decimal part, which can be only 2 digits.

Now I want to put the grouping seperator as the user enters the digits, in real time. When I think of the implementation, I am confused about things like the user deleting the digits or things like the user placing the cursor at the beginning and typing 0 in the front of the entered number, and so…

What would be the cleanest implementation?

Answer 1

OK, here is how:

First, you implement a UITextField category.
Then you say to yourself:

[self addTarget:self action:@selector(formatTextAsNumber) forControlEvents:UIControlEventEditingChanged];

And here is the formatTextAsNumber method that does the charm:

- (void)formatTextAsNumber {

    [self removeTarget:self action:@selector(formatTextAsNumber) forControlEvents:UIControlEventEditingChanged];

    if ([self.text length] > 0) {
        NSString *currentText = [NSString stringWithString:self.text];

        currentText = [currentText stringByReplacingOccurrencesOfString:kGroupingSeperator withString:@""];
        currentText = [currentText stringByReplacingOccurrencesOfString:@"," withString:@"."];

        NSString *suffix = [currentText substringFromIndex:[currentText length] - 1];

        NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
        NSLocale *trLocale = [[[NSLocale alloc] initWithLocaleIdentifier:@"tr_TR"] autorelease];
        [formatter setLocale:trLocale];

        NSNumber *number = [NSNumber numberWithDouble:[currentText doubleValue]];
        [formatter setNumberStyle:NSNumberFormatterDecimalStyle];
        [formatter setGroupingSeparator:@"."];

        NSString *finalText = [formatter stringFromNumber:number];

        if ([suffix isEqualToString:@"."]) {
            finalText = [finalText stringByAppendingString:@","];
        }

        self.text = finalText;
        [formatter release];
    }

    [self addTarget:self action:@selector(formatTextAsNumber) forControlEvents:UIControlEventEditingChanged];
}