Dogs API

note

This tutorial has been kindly provided by @tatadan and forms part of their Wails Examples Repository.

In this tutorial we are going to develop an application that retrieves photos of dogs from the web and then displays them.

Create the project

Let's create the application. From a terminal enter: wails init -n dogs-api -t svelte

Note: We could optionally add -ide vscode or -ide goland to the end of this command if you wanted to add IDE support.

Now let's cd dogs-api and start editing the project files.

Remove unused code

We will start by removing some elements that we know we will not use:

• Open app.go and remove the following lines:

// Greet returns a greeting for the given name
func (a *App) Greet(name string) string {
    return fmt.Sprintf("Hello %s, It's show time!", name)
}

• Open frontend/src/App.svelte and delete all lines.
• Delete the frontend/src/assets/images/logo-universal.png file

Creating our application

Now let's add our new Go code.

Add the following struct declarations to app.go before the function definitions:

type RandomImage struct {
    Message string
    Status  string
}

type AllBreeds struct {
    Message map[string]map[string][]string
    Status  string
}

type ImagesByBreed struct {
    Message []string
    Status  string
}

Add the following functions to app.go (perhaps after the existing function definitions):

func (a *App) GetRandomImageUrl() string {
    response, err := http.Get("https://dog.ceo/api/breeds/image/random")
    if err != nil {
        log.Fatal(err)
    }

    responseData, err := ioutil.ReadAll(response.Body)
    if err != nil {
        log.Fatal(err)
    }

    var data RandomImage
    json.Unmarshal(responseData, &data)

    return data.Message
}

func (a *App) GetBreedList() []string {
    var breeds []string

    response, err := http.Get("https://dog.ceo/api/breeds/list/all")
    if err != nil {
        log.Fatal(err)
    }

    responseData, err := ioutil.ReadAll(response.Body)
    if err != nil {
        log.Fatal(err)
    }

    var data AllBreeds
    json.Unmarshal(responseData, &data)

    for k := range data.Message {
        breeds = append(breeds, k)
    }

    sort.Strings(breeds)

    return breeds
}

func (a *App) GetImageUrlsByBreed(breed string) []string {

    url := fmt.Sprintf("%s%s%s%s", "https://dog.ceo/api/", "breed/", breed, "/images")
    response, err := http.Get(url)
    if err != nil {
        log.Fatal(err)
    }

    responseData, err := ioutil.ReadAll(response.Body)
    if err != nil {
        log.Fatal(err)
    }

    var data ImagesByBreed
    json.Unmarshal(responseData, &data)

    return data.Message
}

Modify the import section of app.go to look like this:

import (
    "context"
    "fmt"
    "encoding/json"
    "io/ioutil"
    "log"
    "net/http"
    "sort"
)

Add the following lines to frontend/src/App.svelte:

<script>
  import { GetRandomImageUrl } from "../wailsjs/go/main/App.js";
  import { GetBreedList } from "../wailsjs/go/main/App.js";
  import { GetImageUrlsByBreed } from "../wailsjs/go/main/App.js";

  let randomImageUrl = "";
  let breeds = [];
  let photos = [];
  let selectedBreed;
  let showRandomPhoto = false;
  let showBreedPhotos = false;

  function init() {
    getBreedList();
  }

  init();

  function getRandomImageUrl() {
    showRandomPhoto = false;
    showBreedPhotos = false;
    GetRandomImageUrl().then((result) => (randomImageUrl = result));
    showRandomPhoto = true;
  }

  function getBreedList() {
    GetBreedList().then((result) => (breeds = result));
  }

  function getImageUrlsByBreed() {
    init();
    showRandomPhoto = false;
    showBreedPhotos = false;
    GetImageUrlsByBreed(selectedBreed).then((result) => (photos = result));
    showBreedPhotos = true;
  }
</script>

<h3>Dogs API</h3>
<div>
  <button class="btn" on:click={getRandomImageUrl}>
    Fetch a dog randomly
  </button>
  Click on down arrow to select a breed
  <select bind:value={selectedBreed}>
    {#each breeds as breed}
      <option value={breed}>
        {breed}
      </option>
    {/each}
  </select>
  <button class="btn" on:click={getImageUrlsByBreed}>
    Fetch by this breed
  </button>
</div>
<br />
{#if showRandomPhoto}
  <img id="random-photo" src={randomImageUrl} alt="No dog found" />
{/if}
{#if showBreedPhotos}
  {#each photos as photo}
    <img id="breed-photos" src={photo} alt="No dog found" />
  {/each}
{/if}

<style>
  #random-photo {
    width: 600px;
    height: auto;
  }

  #breed-photos {
    width: 300px;
    height: auto;
  }

  .btn:focus {
    border-width: 3px;
  }
</style>

Testing the application

To generate the bindings and test the application, run wails dev.

Compiling the application

To compile the application to a single, production grade binary, run wails build.