Extracting a partial is a technique used for removing complex or duplicated view code from your application. This is the equivalent of using long method and extract method in your views and templates.
- Removes duplicated code from views.
- Avoids shotgun surgery by forcing changes to happen in one place.
- Removes divergent change by removing a reason for the view to change.
- Groups common code.
- Reduces view size and complexity.
- Makes view logic easier to reuse, which makes it easier to avoid duplication.
- Create a new file for partial prefixed with an underscore (_filename.html.erb).
- Move common code into newly created file.
- Render the partial from the source file.
Let's revisit the view code for adding and editing questions.
Note: There are a few small differences in the files (the URL endpoint and the label on the submit button).
` app/views/questions/new.html.erb@cec19d8
` app/views/questions/edit.html.erb@cec19d8
First, extract the common code into a partial, remove any instance variables and
use question and url as local variables:
` app/views/questions/_form.html.erb@57f0f48
Move the submit button text into the locales file:
` config/locales/en.yml@57f0f48
Then render the partial from each of the views, passing in the values for
question and url:
` app/views/questions/new.html.erb@57f0f48
` app/views/questions/edit.html.erb@57f0f48
- Check for other occurrences of the duplicated view code in your application and replace them with the newly extracted partial.