part_2.md

Part 2: Sort the list of movies (15 points)

On the list of all movies page, make the column headings for "Movie Title" and "Release Date" into clickable links. Clicking one of them should cause the list to be reloaded but sorted in ascending order on that column. For example, clicking the "release date" column heading should redisplay the list of movies with the earliest-released movies first; clicking the "title" header should list the movies alphabetically by title. (For movies whose names begin with non-letters, the sort order should match the behavior of String#<=>.)

When the listing page is redisplayed with sorting-on-a-column enabled, the column header that was selected for sorting should appear with a yellow-orange background, as shown below. The selected column header should also have 2 additional CSS classes added to it: 1) hilite, and 2) a utility class from the Bootstrap Colors set. You should do this by setting controller variables that are used to conditionally set the CSS class of the appropriate table heading to these new classes.

The result should look something like this:

Note. Initially, you will probably find that when you click on a sort column, the app will "forget" which checkboxes have been checked. Similarly, when you sort on a column but then you change which checkboxes are checked, the app will "forget" the desired sort order. We'll fix these cases next.

IMPORTANT for grading purposes:

The link (that is, the <a> tag) for sorting by "title" should have the HTML element id title_header, and the link for sorting by release date should have the HTML element id release_date_header. The table containing the list of movies should have the HTML element id movies (this has already been set for you by the starter code).

Hint: Adding parameters to existing RESTful routes

The current RottenPotatoes views use the Rails-provided "resource-based routes" helper movies_path to generate the correct URI for the movies index page. You may find it helpful to know that if you pass this helper method a hash of additional parameters, those parameters will be parsed by Rails and available in the params[] hash. To play around with this behavior, you can test out routes in the Rails console. (How did I find this secret information? I Googled "test routes in rails console".)

So, when you are converting those column headers into clickable links (for which it's best to use the link_to helper) that point to the RESTful route for fetching the movie list (best done using the route helper movies_path(), think about how you might modify the call that generates the route helper in order to include information visible in params that would tell you which column header was clicked. Hint: Remember that every parameter in a route has a key and a value, so any argument you pass to movies_path would have to be a hash.

Hint: displaying things in the right order

• Databases are pretty good at returning collections of rows in sorted order according to one or more attributes. Before you rush to sort the collection returned from the database, look at the documentation for ActiveRecord.order and see if you can get the database to do the work for you.

Don't put code in your views! The view shouldn't have to sort the collection itself—its job is just to show stuff. The controller should spoon-feed the view exactly what is to be displayed.

Remembering both the sort order and filtering order

At this point, you should have sort columns working, but you probably noticed that sorting on a column "forgets" the values of which checkboxes were checked. Let's fix that.

The key to fixing it is to remember that when we constructed the form for the checkboxes in part 1, the only thing that was needed to pass the info to the controller about which checkboxes were checked. For example, if the boxes whose field names were ratings_G and ratings_PG were checked, params[:ratings] would contain a hash {'G': '1', 'PG': '1'}. (HTML allows a checked box to be given any value, but we chose "1" which is conventional since the value is usually irrelevant, since if the checkbox is not checked, it doesn't appear in the submitted form values at all.)

So if we could also include this info in the link when the user clicks a column name, the info would be passed into the controller action along with the column name itself!

Now, the view already knows that the value @ratings_to_show is an array containing only the values for the boxes that were checked--for example, something like ['G','R']. But to make it look right for params, we need to pass movies_path() something that looks more like ['G':'1', 'R':'1'] (or really, any value other than '1' is fine, since it's just the presence of the key that matters).

Judiciously using Google, find a concise way to derive a hash whose keys are the values of an array, and whose value for all the keys is some constant like '1'. With that in hand,, modify the arguments to the movies_path() route helper already used by your column headers to include that hash, such that the information about which checkboxes were checked on the form appears as part of the route.

At this point, you should be able to refresh the view by either clicking on a column header or clicking the Refresh button, and both types of changes should be "remembered".

Submission

You'll submit the code for this part after you deploy on Heroku and when you supply your Heroku deployment URL in part 3.

For now, commit all the changes you have made so far, and deploy them to check that they work on Heroku before moving on to the next section:

git commit -am "part 2 complete"
git push heroku master

Next: Part 3: Remember the sorting and filtering settings