Refactoring question: Extract as widget/method/variable... What are pros and cons?

Question

All three of them do basically the same thing. What are the best practices? In which case shall I use which extracting way? What is the standard?

I guess these could be some points that could matter:

• readability
• performance
• number of lines

Example:

Extract the Container. Which way would you prefer and why?

class Example extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

1. Extract Container as Widget (+6 lines):

class Example extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ExtractedAsWidget();
  }
}

class ExtractedAsWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

2. Extract Container as Method (+1 (in some cases 3) line):

class Example extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return buildContainer();
  }

  Container buildContainer() => Container();
}

3. Extract Container as Variable (+1 line):

class Example extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var container = Container();
        return container;
  }
}

Solution

Extracting as Widget is the best practice as the Flutter framework can optimize widgets rather than methods or variables. But for this particular case, I would extract Container as method. Extracting as Widget would be too overkill.

Extracting as Variable

Extracting as variable should only be done when your widget is fixed, being used only in a single file & doesn't need any parameters.

Extracting as Method

Extracting as method should be done when your widget is being used only in a single file (and it can also use some parameters for additional customization). It also increases code readability.

Extracting as Widget

Extracting as Widget is the most optimal way to create a widget that is being used multiple times in different files. Flutter recommends creating as much StatelessWidget as possible.

The most simple example that I can suggest is the use of buttons. Every app has a fixed primary color button that we use. So, instead of creating a variable or method, we should create a StatelessWidget of that button & use that in multiple screens of our app.