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Adding Maps to the Front End

Add Maps to the Front End

To render a map within our front end, we will be using another third party library, react-map-gl.

cd ClientApp
npm install --save react-map-gl
cd ..

Getting another license key for our front-end code.

We will be using mapbox as our mapping information provider. We will visit their website and register for an API key.

We will create a file .env.development.local in the ClientApp directory in the same location as our package.json to store our API key in development. This file defines environment variables for our application. An environment variable is a set of string-based keys and text values associated with the execution of our application. Environment variables control many aspects of our command prompt as well as our running applications. Since these are a per-app configuration, they also serve as a location for values such as API keys.

NOTE: This is a different approach than dotnet takes for its local configuration data. Both are good solutions, each with their issues and benefits. We are using an environment variable since this is the approach that our front-end app setup prefers.

REACT_APP_MAPBOX_TOKEN=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

NOTE: Replace xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx with your token assigned to your mapbox.com account

NOTE: After changing this file, you should stop and restart your dotnet watch run

Once we have installed the library, signed up for a key, and set our API key in configuration, we will update our Restaurants.jsx component to show a map.

Adding the map to the UI

First, we will import ReactMapGL from our library:

import ReactMapGL from 'react-map-gl'

Then, set a state variable to store information about the map's zoom level, size, and coordinates of the center of the map. Here we will use the coordinates of the SDG campus as our map center.

const [viewport, setViewport] = useState({
latitude: 27.77101804911986,
longitude: -82.66090611749074,
zoom: 9.8,
})

With this state, we can replace the static map image with our dynamic map. Inside the ReactMapGL we include a NavigationalControl component, also from mapbox-gl, that shows a small zoom control interface. We also set the map's style to be absolutely positioned to work with our CSS.

<section className="map">
<ReactMapGL
{...viewport}
style={{ position: 'absolute' }}
width="100%"
height="100%"
mapboxApiAccessToken={process.env.REACT_APP_MAPBOX_TOKEN}
>
<div style={{ position: 'absolute', left: 10 }}>
<NavigationControl />
</div>
</ReactMapGL>
</section>

You will notice that we are taking all the attributes of our viewport state and spreading them into the ReactMapGL. We carefully chose the name of this state variable's properties to correspond to the various properties of the map we wish to control. Also, notice that we provide the mapboxApiAccessToken here as well. To access the value we placed in the .env.development.local file, we use process.env, which is an object containing all the environment variables configured for the current process (app).

Moving around the map

You may notice that we cannot adjust the map by dragging while we can render a map and see a particular area. Using mouse dragging is a standard interface, so we will add that feature. Luckily, again, our viewport state is set up correctly to allow us to handle this.

The ReactMapGL expects a property for onViewportChange that is a method that takes new values for a viewport change. And since our setViewport is exactly such a function we can use it by adding this to ReactMapGL

<ReactMapGL
{...viewport}
onViewportChange={setViewport}
mapboxApiAccessToken={process.env.REACT_APP_MAPBOX_TOKEN}
></ReactMapGL>

Try dragging, pinching, and zooming the map!

Adding pins to the map

If we wish to add pins to the map, we must render an array of <Marker> components inside our ReactMapGL component. A <Marker> is another map-gl component. It requires a latitude and longitude property. Luckily for us, our restaurants state now has that information from our api!

We can use our old friend the JavaScript map() function to generate these markers.

When generating the array of <Marker> elements, we specify the latitude and longitude from the specific restaurant. We then render each marker's visual as anything we like; here, we just use the existing emoji character. We could use text, an image, or any other react component as the marker representation.

<ReactMapGL
{...viewport}
onViewportChange={setViewport}
mapboxApiAccessToken={process.env.REACT_APP_MAPBOX_TOKEN}
>
{restaurants.map(restaurant => (
<Marker
key={restaurant.id}
latitude={restaurant.latitude}
longitude={restaurant.longitude}
>
<span role="img" aria-label="taco">
🌮
</span>
</Marker>
))}
</ReactMapGL>

Adding interaction to the map

Next, we will show details of a restaurant when the user clicks its marker.

To do that, we will add another state variable to track the selectedMapRestaurant and initially set that value to null. When this variable is null, no restaurant is selected on the map. When this variable is not null, the value is the restaurant we want to show.

const [selectedMapRestaurant, setSelectedMapRestaurant] = useState(null)

Then just before we render our array of <Marker>, we will add this code:

{
selectedMapRestaurant ? (
<Popup
latitude={selectedMapRestaurant.latitude}
longitude={selectedMapRestaurant.longitude}
closeButton={true}
closeOnClick={false}
onClose={() => setSelectedMapRestaurant(null)}
offsetTop={-5}
>
<div>
<p>{selectedMapRestaurant.name}</p>
<p>{selectedMapRestaurant.description}</p>
</div>
</Popup>
) : null
}

If there is a selectedMapRestaurant, a map-gl based Popup component is rendered at the coordinates of the selected restaurant. We also define an onClose, which the popup will use to dismiss itself. For that, we simply set the selectedMapRestaurant to null. Inside the popup, we will render a few details of the restaurant.

Lastly, we need to add an onClick for our <Marker> so we can set the value of selectedMapRestaurant

<span
role="img"
aria-label="taco"
onClick={() => setSelectedMapRestaurant(restaurant)}
>
🌮
</span>

When clicking on markers, you may notice that the popup appears behind other markers on the page. To resolve this, add the following CSS to your project:

.mapboxgl-popup {
z-index: 1;
}

Now we have a zoomable, draggable, and clickable map that represents data pulled from our API.

NOTE: If you are going to deploy this with Heroku, you'll need to run heroku config:set REACT_APP_MAPBOX_TOKEN="xxxx" with your specific key in place of xxxx at least once before you deploy.

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