Dogs API

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.