Mastering Ruby Closures: A Guide to Blocks, Procs, and Lambdas by Benjamin Tan Wei Hao

Author:Benjamin Tan Wei Hao [Hao, Benjamin Tan Wei]
Language: eng
Format: epub, pdf
Tags: Pragmatic Bookshelf
Publisher: Pragmatic Bookshelf
Published: 2017-08-15T23:00:00+00:00

Implementing a Router DSL

In the previous section, you saw one flavor of object initialization using blocks. Here’s another example, adapted and modified from Rails. Let’s imagine that you want to define a bunch of routes in a web framework, such as Rails. Routes are rules that you declare for an incoming web request. These rules invoke the appropriate controller and controller method, depending on the pattern of the URL of the incoming web request. For example, if the web server receives a request with http://localhost:3000/users, a route would parse the incoming request URL and ensure that the index method of the UsersController will be invoked.

In Rails, this file is located in config/routes.rb. In older versions of Rails, the syntax looked like this:

routes = Router.new do |r|

r.match '/about' => 'home#about'

r.match '/users' => 'users#index'

end

However, as Rails evolved, the way routes were defined also changed:

routes = Router.new do

match '/about' => 'home#about'

match '/users' => 'users#index'

end

In the new syntax, the block no longer expects an argument. With nothing to pass into yield, which object does match belong to? Learning the techniques in creating this variation to object instantiation will also allow you to create DSLs.

Create a file called router.rb, and fill it in with this initial implementation:

routes = Router.new do

match '/about' => 'home#about'

match '/users' => 'users#index'

end

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