微信發紅包UITextField金額輸入格式化

UITextField是iOS上常用的輸入框，對其輸入進行格式化顯示是常態，這兒羅列兩種常用格式化:
微信發紅包UITextField金額輸入格式化，
銀行卡格式化
消化後就可以自己寫其他格式化樣式。

微信發紅包UITextField金額輸入格式化

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSString *text             = _textField.text;
    NSString *decimalSeperator = @".";
    NSCharacterSet *charSet    = nil;
    NSString *numberChars      = @"0123456789";

    if ([string isEqualToString:decimalSeperator] && [text length] == 0) {
        return NO;
    }

    NSRange decimalRange = [text rangeOfString:decimalSeperator];
    BOOL isDecimalNumber = (decimalRange.location != NSNotFound);
    if (isDecimalNumber) {
        charSet = [NSCharacterSet characterSetWithCharactersInString:numberChars];
        if ([string rangeOfString:decimalSeperator].location != NSNotFound) {
            return NO;
        }
    }
    else {
        numberChars = [numberChars stringByAppendingString:decimalSeperator];
        charSet = [NSCharacterSet characterSetWithCharactersInString:numberChars];
    }

    NSCharacterSet *invertedCharSet = [charSet invertedSet];
    NSString *trimmedString = [string stringByTrimmingCharactersInSet:invertedCharSet];
    text = [text stringByReplacingCharactersInRange:range withString:trimmedString];

    if (isDecimalNumber) {
        NSArray *arr = [text componentsSeparatedByString:decimalSeperator];
        if ([arr count] == 2) {
            if ([arr[1] length] > 2) {
                return NO;
            }
        }
    }

    textField.text = text;
    return NO;
}

銀行卡格式化

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    NSString *text = [textField text];

    NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
    string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];
    if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {
        return NO;
    }

    text = [text stringByReplacingCharactersInRange:range withString:string];
    text = [text stringByReplacingOccurrencesOfString:@" " withString:@""];

    NSString *newString = @"";
    while (text.length > 0) {
        NSString *subString = [text substringToIndex:MIN(text.length, 4)];
        newString = [newString stringByAppendingString:subString];
        if (subString.length == 4) {
            newString = [newString stringByAppendingString:@" "];
        }
        text = [text substringFromIndex:MIN(text.length, 4)];
    }

    newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];

    if (newString.length >= 24) {
        return NO;
    }
    textField.text = newString;

    return NO;
}