如何根据“清洁代码”原则处理按钮点击？

Question

I have the following, seemingly simple piece of code handling button taps in an iOS application:

- (IBAction)tapKeypadButton:(UIButton *)sender {
    NSString *buttonLabel = sender.titleLabel.text;

    if ([buttonLabel isEqualToString:@"<"]) {
        [self _tapBackButton];
    } else {
        [self _tapDigitButton:buttonLabel];
    }
}

To completely follow the Clean Code principles by Robert C. Martin, would I need a ButtonTapFactory or something in the same line?

Answer 1

You have two types of buttons, with different behaviors (back button and digit button). To make this code clean, you should have two actions for each type. The type should not be determined by the contents of the text inside the button, but through a semantically meaningful way. (ie subclass). Further, an action method should only contain a call to another method that does the actual logic. Everything else is not testable. In code:

- (IBAction) tapBackButton:(id) sender
{
    [self _tapBackButton:sender];
}

- (IBAction) tapDigitButton:(id) sender
{
    [self _tapDigitButton:sender];
}

This way you can have unit tests calling your methods without your UI code interfering. Please also note that I removed the label from the call to _tapDigitButton . The digit should not be parsed from the label, but be passed in a more semantically stable way, for example using the tag property.