Groups of routes

Groups of routes

Imagine we are building an application that allows managing the members of our study group. There’s a way to

• list all the members
• look at a member’s details
• add a new member
• update a member’s details
• remove a member

That’s exactly what a lot of web applications do, with certain variations.

Almost all web applications that you use on a daily basis will, in some way or the other, have lists of things. Amazon has lists of goods, and so has Ebay. Facebook has lists of posts, and so has Twitter. Gmail obviously has lists of emails, and so on, and so on. Usually there’s a way to display details for these things, to create new instances (e.g. by publishing a post on Facebook), editing, and deleting them.

Because this is such a common scheme, Rails has added a first class concept for this. And, as we do, we are going to re-implement it in Sinatra. This way you’ll have a great understanding of what a “resource” is in Rails once you get started with that framework.

Also, for our purposes we’ll deviate from Rails just a little bit. And we’ll explain that later.

In a nutshell, Rails defines a resource as a collection of routes that deal with the same “thing”. In our example we deal with “members”, so our resource will be members.

Here’s what the routes that make up our resouce look like:

• GET /members displays a list of all members
• GET /members/:id displays the details for a single member
• GET /members/new displays a form for creating a new member
• POST /members creates a new member from that form
• GET /members/:id/edit displays a form for editing a member’s details
• PUT /members/:id updates a member’s details from that form
• GET /members/:id/delete asks for confirmation to delete the member
• DELETE /members/:id deletes the member

Here’s the same information as a table. Note that we also give names to these routes [1]:

These names are the same as the ones that Rails uses, too. We’ll use these names for our templates, in case we need a template. Naming them the same for every resource that we write, ever, helps others to understand what we’re talking about in an instant.

So lets look at the routes more. If you look at the purpose of our routes, there are 4 groups:

• index and show are used to display existing data.
• new and create are used to create a new member.
• edit and update are used to update a member.
• delete and destroy are used to delete a member

The two pairs new and create as well as edit and update would follow the same pattern that we’ve discussed in the chapter about Validations:

• The first one request GETs an HTML form for the user to enter some data.
• This form is then submitted as another request, using POST or PUT, to the second route.
• The second route validates the data.
• If the data is valid it creates/updates the member, and redirects to the show view, passing a confirmation message.
• If the data is not valid it re-renders the form with an error message.

For the last pair there’s no validation, of course. Instead we just delete the object and redirect to the index view.

However there’s a problem with all this:

Today’s browsers still do not allow sending HTTP requests using any other verb than GET and POST.

Ouch.

So what do we do?

We fake that. Let’s see …

Footnotes

[1] For our purposes here we have deviated from Rails a little, and added an 8th route: GET /members/:id/delete. This route displays a page that asks for a confirmation to delete. In Rails this is solved with a little Javascript box that pops up and asks this question. However, we don’t want to get into Javascript too much just yet, and adding this route is a just as valid solution, too. In fact, some web applications out there prefer this over the Javascript solution.