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Franciscello
Franciscello

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A Crystal Mint Lemonade๐Ÿน๐Ÿƒ

#mint #crystal #webdev #tutorial

Hi everyone!๐Ÿ‘‹
It's been a while since my last post, but I have a good reason: I was on vacations! Yeah! ๐Ÿ˜โ˜€๏ธ๐Ÿ–

And now it is time for a new Mint/Crystal recipe: we are going to build a Client/Server application using Mint for the frontend (this post) and Crystal for the backend (the next post)!

So let's start ... but first:
may I have a Crystal Mint Lemonade? โ˜๏ธ๐Ÿน๐Ÿƒ

The Application

We are going to build an application that will list four (not 3, nor 5 but 4!) non-alcoholic summer drinks (as shown in the post 4 Refreshing Summer Drinks)

The Frontend

In this post we are going to build the frontend of our application ... uh oh! wait! We don't have a name for our application ... mmm let me think ... it will be called: Summer drinks! ๐Ÿน

And as we already mention, we are going to build the frontend using Mint!

We won't be doing a step-by-step tutorial but instead we are going to show the highlights of the source code.

The Structure

The project's structure is inspired by Mint Realworld and is the following:

mint-front
  |
  |- public
  |- source
  |   |- components
  |   |- entities
  |   |- pages
  |   |- stores
  |   |- Main.mint
  |   |- Routes.mint
  |
  |- mint.json

Routing

Routing in Mint is really simple. For our application we need 3 routes:

mint-front/source/Routes.mint

routes {
  / {
    Application.navigateTo(Page::Home)
  }

  /drinks {
    parallel {
      Application.navigateTo(Page::Drinks)
      Stores.Drinks.load()
    }
  }

  * {
    Application.navigateTo(Page::NotFound)
  }
}

What's important here is that when navigating to /drinks:

  • we start loading the drinks
  • and in parallel we start rendering the view.

In the Application store we are going to save the current page:

mint-front/source/stores/Application.mint

store Application {
  state page : Page = Page::Home

  fun navigateTo (page : Page) : Promise(Never, Void) {
    sequence {
      next { page = page}
      Http.abortAll()
    }
  }
}

And the Main component will be responsible for rendering the correct view given the current page:

mint-front/source/Main.mint

component Main {
  connect Application exposing { page }

  fun render : Html {
    <Layout>
      case (page) {
        Page::Home =>
          <Pages.Home/>

        Page::Drinks =>
          <Pages.Drinks/>

        Page::NotFound =>
          <div>"Where am I?!"</div>
      }
    </Layout>
  }
}

Entities

We will be working with just one entity: the Drink itself! Here's the definition and the way to create an empty one:

mint-front/source/entities/Drink.mint

record Drink {
  id : Number,
  icon : String,
  name : String,
  url : String
}

module Drink {
  fun empty : Drink {
    {
      id = 0,
      icon = "",
      name = "",
      url = ""
    }
  }
}

Requesting the drinks

Here's an excerpt of the function #Stores.Drinks.load() showing the request we send to the server:

mint-front/source/stores/Drinks.mint

  fun load() : Promise(Never, Void) {
    sequence {
      next { status = Stores.Status::Loading }

      response = "https://demo5780178.mockable.io/drinks"
                |> Http.get()
                |> Http.header("Content-Type", "application/json")
                |> Http.send()

      newStatus = case (response.status) {
                    404 => Stores.Status::Error("Not Found")
                        =>  try {
                              /* parse JSON */
                              object = Json.parse(response.body)
                                      |> Maybe.toResult("")

                              /* JSON to Drinks */
                              drinks = decode object as Stores.Status.Drinks

                              Stores.Status::Ok(drinks)

                            } catch Object.Error => error {
                              Stores.Status::Error("Could not decode the response.")
                            } catch String => error {
                              Stores.Status::Error("Could not parse the response.")
                            }
                  }

      next { status = newStatus }

...

In sequence, we will:

  • update the status to loading.
  • send the request (waiting for the response).
  • define the new status given the response. If the response was successful then we try to parse the drinks in the response.
  • and finally, we change the status.

Another important element here is how we implement the different status. We use enums like this:

enum Stores.Status(a) {
  Initial
  Loading
  Error(String)
  Ok(a)
}

Notice how easy is to send the request and handle the response (parse and decode the JSON data)! ๐Ÿค“

Listing the drinks (the Drinks component)

This component will be responsible of showing the list of drinks. So first it needs to connect to the store:

mint-front/source/components/Drinks.mint

component Drinks {
  connect Stores.Drinks exposing { status }

  ...
}

Then the rendering depends on the current status (here we only show the cases Loading and Ok):

component Drinks {
  connect Stores.Drinks exposing { status }

  ...

  fun render : Html {
    case (status) {
      ...

      Stores.Status::Loading =>
        <div::base>
          <div::message>
            "Loading drinks..."
          </div>
        </div>

      ...

      Stores.Status::Ok =>
        <div>
          <{ drinksItems }>
        </div>
    }
  }
}

drinkItems and drinks are computed properties that extract the data from the status:

  get drinks : Array(Drink) {
    case (status) {
      Stores.Status::Ok data => data.drinks
      => []
    }
  }

  get drinksItems : Array(Html) {
    drinks
    |> Array.map((drink : Drink) : Html { <Drinks.Item drink={drink}/> })
    |> intersperse(<div::divider/>)
  }

Notice that each drink is rendered by the component Drinks.Item.

The Full Client Application ๐Ÿค“๐Ÿน

Alt Text

Here is the source code of the recipe! And remember that we run the application using: ๐Ÿš€

$ mint-lang start
Mint - Running the development server
โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”โ”
โš™ Ensuring dependencies... 279ฮผs
โš™ Parsing files... 19.301ms
โš™ Development server started on http://127.0.0.1:3000/

Mocking the Backend

We still have not implemented the backend but we may use Mockable.io to mock it. Here is the response we need:

{
 "drinks": [{
    "id": 1,
    "icon": "๐Ÿ“",
    "name": "Strawberry Limeade",
    "url": "https://www.youtube.com/watch?v=SqSZ8po1tmU"
 }, {
    "id": 2,
    "icon": "โ›ฑ",
    "name": "Melon Sorbet Float",
    "url": "https://www.youtube.com/watch?v=hcqMtASkn8U"
 }, {
    "id": 3,
    "icon": "๐Ÿจ",
    "name": "Raspberry Vanilla Soda",
    "url": "https://www.youtube.com/watch?v=DkARNOFDnwA"
 }, {
    "id": 4,
    "icon": "๐ŸŒด",
    "name": "Cantaloupe Mint Agua Fresca",
    "url": "https://www.youtube.com/watch?v=Zxz-DYSKcIk"
 }]
}

Also notice that the request URL is hardcoded in mint-front/source/stores/Drinks.mint ๐Ÿ™ˆ

Farewell and see you later. Summing up.

We've reached the end of the recipe!๐Ÿ‘จโ€๐Ÿณ We have implemented our second application in Mint๐Ÿƒ:

  • using stores for saving the state of our application (current page and drinks)
  • using enums to implement the different status.
  • using components with conditional rendering (given the current status)

And remember that, in the next recipe, we will implement the server in Crystal! ๐Ÿ’ช๐Ÿค“

Hope you enjoyed it! Until next recipe!๐Ÿ‘จโ€๐Ÿณ๐Ÿน

Photo by Jamie Street on Unsplash

Top comments (1)

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Szikszai Gusztรกv •

Very nice post! I'm always psyched to see posts about Mint ๐Ÿƒ