Merge pull request #1 from trevorblades/example

Example

README.md

@@ -4,14 +4,14 @@
 [![Donate](https://img.shields.io/beerpay/trevorblades/countries.svg)](https://beerpay.io/trevorblades/countries)
 
 
-A public GraphQL API for information about countries, continents, and languages. This project uses [Countries List](https://annexare.github.io/Countries/) as a data source, so the schema follows the shape of that data, with a couple exceptions:
+A public GraphQL API for information about countries, continents, and languages. This project uses [Countries List](https://annexare.github.io/Countries/) as a data source, so the schema follows the shape of that data, with a few exceptions:
 
 1. The codes used to key the objects in the original data are available as a `code` property on each item returned from the API.
 2. The `continent` and `languages` properties are now objects and arrays of objects, respectively.
 
-Check out the [playground](https://countries.trevorblades.com) to explore the schema and test out some queries.
+## Querying
 
-## Example
+In:
 
 ```graphql
 {
@@ -28,6 +28,8 @@ Check out the [playground](https://countries.trevorblades.com) to explore the sc
 }
 ```
 
+Out:
+
 ```json
 {
   "data": {
@@ -46,3 +48,97 @@ Check out the [playground](https://countries.trevorblades.com) to explore the sc
   }
 }
 ```
+
+Check out [the playground](https://countries.trevorblades.com) to explore the schema and test out some queries.
+
+## Example
+
+One practical use of this API is to create a country select field that fetches its options dynamically. Normally, you would need to install an npm package or create a file in your project containing the necessary data -- usually country codes and names -- and bundle that data with your app code. This results in a lot of extra kilobytes hanging around in your bundle for a feature that might not always get rendered or used. Here's what that data size looks like:
+
+- **50.1 KB** with the `countries` export from [Countries List](https://annexare.github.io/Countries/)
+- **14.2 KB** with this API (~70% smaller)
+
+In this example, I'll be using [React](https://reactjs.org/) and some [Apollo](https://apollographql.com) tools. Apollo's GraphQL client and React components make it simple to execute, handle, and cache GraphQL queries. You can also accomplish this by sending a POST request to this API using `fetch` or your favourite request library, but I won't cover that in this example.
+
+### 1. Install dependencies
+
+```shell
+$ npm install react react-dom react-apollo apollo-boost graphql graphql-tag
+```
+
+### 2. Build a React component
+
+```js
+import ApolloClient from 'apollo-boost';
+import React, {Component} from 'react';
+import ReactDOM from 'react-dom';
+import gql from 'graphql-tag';
+import {Query} from 'react-apollo';
+
+// initialize a GraphQL client
+const client = new ApolloClient({
+  uri: 'https://countries.trevorblades.com'
+});
+
+// write a GraphQL query that asks for names and codes for all countries
+const GET_COUNTRIES = gql`
+  {
+    countries {
+      name
+      code
+    }
+  }
+`;
+
+// create a component that renders an API data-powered select input
+class CountrySelect extends Component {
+  constructor(props) {
+    super(props);
+
+    // set a default value
+    this.state = {
+      country: 'US'
+    };
+  }
+  
+  // set the selected country to the new input value
+  onCountryChange(event) {
+    this.setState({country: event.target.value});
+  }
+
+  render() {
+    return (
+      <Query query={GET_COUNTRIES} client={client}>
+        {({loading, error, data}) => {
+          if (loading) return <p>Loading...</p>;
+          if (error) return <p>{error.message}</p>;
+          return (
+            <select
+              value={this.state.country}
+              onChange={this.onCountryChange.bind(this)}
+            >
+              {data.countries.map(country => (
+                <option key={country.code} value={country.code}>
+                  {country.name}
+                </option>
+              ))}
+            </select>
+          );
+        }}
+      </Query>
+    );
+  }
+}
+
+ReactDOM.render(<CountrySelect />, document.getElementById('root'));
+```
+
+### 3. ???
+
+### 4. Profit 🎉
+
+![faa4bd37fe24eed92b9e4453910b95b3](https://user-images.githubusercontent.com/1216917/48295448-add11200-e440-11e8-8215-95ed3b031cf9.gif)
+
+Now you've got a slick, self-contained country select component that only fetches its data when it's mounted. That means that if it exists within an unmounted route or the falsey end of a condition, it doesn't request any data or take up any extra space in your bundle.
+
+This is just one of many interesting things that you can build with this API. If you create something cool using this, let me know and I'll give you a shoutout here.