Most search requirements are pretty simple and can be satisfied without a search backend. Keeping the code clean and testable is easier with this manager based design pattern.
Not every search feature requires a third-party search system, like Haystack coupled with ElasticSearch. In fact a great many are served sufficiently well by basic SQL querying: A case-insensitive similarity query on a single character field, e.g. a title or description. Not even full-text search is required.
In a simple search view you might write something like this to let a user search for and filter a list of countries:
There’s nothing too complex here, but with additional filtering fields or more complicated logic, it might not be something you want left to the view function. Especially when testing is considered.
Since this deals with pulling from an entire database table it makes sense to consider a manager for our solution.
Moving the search operations out of the view makes the view simpler, keeps like functionality together, makes the code portable, and makes testing much saner.
One of the goals is a clean interface, so to keep this simple we should be able to pass in a dictionary of search and filtering parameters. Turns out our search form already provides just the dictionary we want.
Now all the search and filtering logic can be encapsulated in the manager method, and tested separately from the view.
Again, this small example might not look like it needs much testing, but more complicated filtering scenarios typically do. Maintaining the logic in the manager (or queryset) method makes it testable without needing to go through the exercise of loading views with HTTP requests and examining the responses.
Now the logic in the view is far simpler and will remain this simple regardless of what’s added to the search form.
You don’t have to use the form to validate the data, instead passing the request GET dictionary to the search method directly, however it’s good practice to clean this before sending it to our query.
Our view could be made yet more compact by adding and calling a method on the form class like so:
This is how Haystack’s
SearchForm works. Here however it only serves
to move a single conditional statement down the chain and doesn’t
provide any significant benefits beyond one more level of “porcelain”.