Creating an API with fez, Kemal and Crystal

This is a very basic example on using fez to generate a Kemal API, running on Crystal

1. Install Crystal

    $ brew install crystal-lang --with-llvm
   

   Using --with-llvm can be added to participate in the language development.

2. Clone fez to use it as a generator

    $ git clone git@github.com:jwoertink/fez.git
    $ cd fez/
    $ make
   

   You can also use homebrew to install fez.

3. Create a sample API

    $ bin/fez crystal_kemal_api -t api -d ~/dev/crystal
   

   Will create an API in ~/dev/crystal

4. Your app will have 2 primary dependencies to run.

   • Ruby
   • Crystal

   If you have those two installed, then your next step is to cd in to your new app’s directory and run make install.

    $ cd crystal_kemal_api
    $ make install
   

5. To run the app, you can either:

   • make run - This compiles your assets in to their natural form, and then boots kemal.
   • guard - This will boot your kemal and then watch for any changes to the files.

   Both of these options will boot a server on localhost:3001. The difference is that using guard allows you to do live-reloading.

   An output example of running make run:

    $ make run
    crystal app.cr
    [development] Kemal is ready to lead at http://0.0.0.0:3001
   

6. Let’s make the “controller” (on src/crystal_kemal_api.cr) slightly more interesting

    api("v1") do
      # /v1/test.json
      get "/health" do |env|
        {"message" => "Welcome to Kemal running on Crystal :)"}.to_json
      end
    end
   

7. Re-run and check the output

    $ curl 'localhost:3001/v1/health.json' | jq .
   

   Should return

    {
      "message": "Welcome to Kemal running on Crystal :)"
    }
   

Enjoy! ;)