- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSCharacterSet *charSet = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] invertedSet];
NSString *filteredStr = [[string componentsSeparatedByCharactersInSet:charSet] componentsJoinedByString:@""];
if ([string isEqualToString:filteredStr]) {
return YES;
}
return NO;
}