Chapter 4: Creating a new project
Up until now we’ve used the crystal
command to only run our code.
Actually crystal
command is pretty useful and does lot more than that. (check crystal --help
for more)
For example we can use it to create a new Crystal project.
Awesome. crystal
helped us create a new project. Let’s see what it did for us.
Created a new folder named sample
Created a LICENSE
Created
shard.yml
for dependency management.Initialized an empty Git repository
Created a README for our project
Created
src
andspec
folders to put our code and tests(ssh..we’ll talk about it soon) in it.
Let’s run it.
Nothing! Yay :)
Now that we create our first project. Let’s use some external libraries.
Using Shards for dependency management
To manage dependencies of a project we use shards
. shards
is like bundler
and shard.yml
is like Gemfile
.
awesome-crystal has a curated list of Crystal shards.
crystalshards.org lists all of the available Crystal shards on GitHub (similar to rubygems.org)
Let’s open up shard.yml
.
This is a default shard.yml
and it contains the minimal necessary information about our project. Those are
name
specifies the name of the projectversion
specifies the version of the project. Crystal itself uses semver for version management so it’s a good convention for you to follow.authors
section specifies the authors of the project. By default this is taken from your globalgit
configuration.crystal
specifies the version of Crystal that the project is using.license
specifies the type of your project license. By default this isMIT
.
Okay. That’s great but what can we do with this shard.yml
? Well we can use this file to add external libraries(we call it dependency) and manage them without even worrying about any folders / paths e.g.. Sweet isn’t it?
Now that we know the true power of shards
let’s add Kemal to our shard.yml
and build a simple web application :)
Open up shard.yml
. First we need to add Kemal
as a dependency to our project. We do this by including
That’s great! Now we added Kemal
to our project. First, we need to install it.
Okay now we are ready to use Kemal
in our project. Open up src/sample.cr
Look how we used require
to access Kemal
in our program.
Let’s run.
Go to localhost:3000
and see it in action!
Now you know how to add dependencies and use others’ shard
s :)
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