Commit 9f037034 authored by Filipa Lacerda's avatar Filipa Lacerda Committed by Phil Hughes

Adds documentation to use Vuex

parent 365adfa5
...@@ -28,8 +28,9 @@ As always, the Frontend Architectural Experts are available to help with any Vue ...@@ -28,8 +28,9 @@ As always, the Frontend Architectural Experts are available to help with any Vue
All new features built with Vue.js must follow a [Flux architecture][flux]. All new features built with Vue.js must follow a [Flux architecture][flux].
The main goal we are trying to achieve is to have only one data flow and only one data entry. The main goal we are trying to achieve is to have only one data flow and only one data entry.
In order to achieve this goal, each Vue bundle needs a Store - where we keep all the data -, In order to achieve this goal, you can either use [vuex](#vuex) or use the [store pattern][state-management], explained below:
a Service - that we use to communicate with the server - and a main Vue component.
Each Vue bundle needs a Store - where we keep all the data -,a Service - that we use to communicate with the server - and a main Vue component.
Think of the Main Vue Component as the entry point of your application. This is the only smart Think of the Main Vue Component as the entry point of your application. This is the only smart
component that should exist in each Vue feature. component that should exist in each Vue feature.
...@@ -74,6 +75,59 @@ provided as a prop to the main component. ...@@ -74,6 +75,59 @@ provided as a prop to the main component.
Don't forget to follow [these steps.][page_specific_javascript] Don't forget to follow [these steps.][page_specific_javascript]
### Bootstrapping Gotchas
#### Providing data from Haml to JavaScript
While mounting a Vue application may be a need to provide data from Rails to JavaScript.
To do that, provide the data through `data` attributes in the HTML element and query them while mounting the application.
_Note:_ You should only do this while initing the application, because the mounted element will be replaced with Vue-generated DOM.
The advantage of providing data from the DOM to the Vue instance through `props` in the `render` function
instead of querying the DOM inside the main vue component is that makes tests easier by avoiding the need to
create a fixture or an HTML element in the unit test. See the following example:
```javascript
// haml
.js-vue-app{ data: { endpoint: 'foo' }}
document.addEventListener('DOMContentLoaded', () => new Vue({
el: '.js-vue-app',
data() {
const dataset = this.$options.el.dataset;
return {
endpoint: dataset.endpoint,
};
},
render(createElement) {
return createElement('my-component', {
props: {
endpoint: this.isLoading,
},
});
},
}));
```
#### Accessing the `gl` object
When we need to query the `gl` object for data that won't change during the application's lyfecyle, we should do it in the same place where we query the DOM.
By following this practice, we can avoid the need to mock the `gl` object, which will make tests easier.
It should be done while initializing our Vue instance, and the data should be provided as `props` to the main component:
##### example:
```javascript
document.addEventListener('DOMContentLoaded', () => new Vue({
el: '.js-vue-app',
render(createElement) {
return createElement('my-component', {
props: {
username: gon.current_username,
},
});
},
}));
```
### A folder for Components ### A folder for Components
This folder holds all components that are specific of this new feature. This folder holds all components that are specific of this new feature.
...@@ -89,6 +143,29 @@ in one table would not be a good use of this pattern. ...@@ -89,6 +143,29 @@ in one table would not be a good use of this pattern.
You can read more about components in Vue.js site, [Component System][component-system] You can read more about components in Vue.js site, [Component System][component-system]
#### Components Gotchas
1. Using SVGs in components: To use an SVG in a template we need to make it a property we can access through the component.
A `prop` and a property returned by the `data` functions require `vue` to set a `getter` and a `setter` for each of them.
The SVG should be a computed property in order to improve performance, note that computed properties are cached based on their dependencies.
```javascript
// bad
import svg from 'svg.svg';
data() {
return {
myIcon: svg,
};
};
// good
import svg from 'svg.svg';
computed: {
myIcon() {
return svg;
}
}
```
### A folder for the Store ### A folder for the Store
The Store is a class that allows us to manage the state in a single The Store is a class that allows us to manage the state in a single
...@@ -430,11 +507,23 @@ describe('Todos App', () => { ...@@ -430,11 +507,23 @@ describe('Todos App', () => {
}); });
}); });
``` ```
#### `mountComponent` helper
There is an helper in `spec/javascripts/helpers/vue_mount_component_helper.js` that allows you to mount a component with the given props:
```javascript
import Vue from 'vue';
import mountComponent from 'helpers/vue_mount_component_helper.js'
import component from 'component.vue'
const Component = Vue.extend(component);
const data = {prop: 'foo'};
const vm = mountComponent(Component, data);
```
#### Test the component's output #### Test the component's output
The main return value of a Vue component is the rendered output. In order to test the component we The main return value of a Vue component is the rendered output. In order to test the component we
need to test the rendered output. [Vue][vue-test] guide's to unit test show us exactly that: need to test the rendered output. [Vue][vue-test] guide's to unit test show us exactly that:
### Stubbing API responses ### Stubbing API responses
[Vue Resource Interceptors][vue-resource-interceptor] allow us to add a interceptor with [Vue Resource Interceptors][vue-resource-interceptor] allow us to add a interceptor with
the response we need: the response we need:
...@@ -481,6 +570,198 @@ new Component({ ...@@ -481,6 +570,198 @@ new Component({
new Component().$mount(); new Component().$mount();
``` ```
## Vuex
To manage the state of an application you may use [Vuex][vuex-docs].
_Note:_ All of the below is explained in more detail in the official [Vuex documentation][vuex-docs].
### Separation of concerns
Vuex is composed of State, Getters, Mutations, Actions and Modules.
When a user clicks on an action, we need to `dispatch` it. This action will `commit` a mutation that will change the state.
_Note:_ The action itself will not update the state, only a mutation should update the state.
#### File structure
When using Vuex at GitLab, separate this concerns into different files to improve readability. If you can, separate the Mutation Types as well:
```
└── store
├── index.js # where we assemble modules and export the store
├── actions.js # actions
├── mutations.js # mutations
├── getters.js # getters
└── mutation_types.js # mutation types
```
The following examples show an application that lists and adds users to the state.
##### `index.js`
This is the entry point for our store. You can use the following as a guide:
```javascript
import Vue from 'vue';
import Vuex from 'vuex';
import * as actions from './actions';
import * as mutations from './mutations';
Vue.use(Vuex);
export default new Vuex.Store({
actions,
getters,
state: {
users: [],
},
});
```
_Note:_ If the state of the application is too complex, an individual file for the state may be better.
#### `actions.js`
An action commits a mutatation. In this file, we will write the actions that will call the respective mutation:
```javascript
import * as types from './mutation-types'
export const addUser = ({ commit }, user) => {
commit(types.ADD_USER, user);
};
```
To dispatch an action from a component, use the `mapActions` helper:
```javascript
import { mapActions } from 'vuex';
{
methods: {
...mapActions([
'addUser',
]),
onClickUser(user) {
this.addUser(user);
},
},
};
```
#### `getters.js`
Sometimes we may need to get derived state based on store state, like filtering for a specific prop. This can be done through the `getters`:
```javascript
// get all the users with pets
export getUsersWithPets = (state, getters) => {
return state.users.filter(user => user.pet !== undefined);
};
```
To access a getter from a component, use the `mapGetters` helper:
```javascript
import { mapGetters } from 'vuex';
{
computed: {
...mapGetters([
'getUsersWithPets',
]),
},
};
```
#### `mutations.js`
The only way to actually change state in a Vuex store is by committing a mutation.
```javascript
import * as types from './mutation-types'
export default {
[types.ADD_USER](state, user) {
state.users.push(user);
},
};
```
#### `mutations_types.js`
From [vuex mutations docs][vuex-mutations]:
> It is a commonly seen pattern to use constants for mutation types in various Flux implementations. This allows the code to take advantage of tooling like linters, and putting all constants in a single file allows your collaborators to get an at-a-glance view of what mutations are possible in the entire application.
```javascript
export const ADD_USER = 'ADD_USER';
```
### How to include the store in your application
The store should be included in the main component of your application:
```javascript
// app.vue
import store from 'store'; // it will include the index.js file
export default {
name: 'application',
store,
...
};
```
### Vuex Gotchas
1. Avoid calling a mutation directly. Always use an action to commit a mutation. Doing so will keep consistency through out the application. From Vuex docs:
> why don't we just call store.commit('action') directly? Well, remember that mutations must be synchronous? Actions aren't. We can perform asynchronous operations inside an action.
```javascript
// component.vue
// bad
created() {
this.$store.commit('mutation');
}
// good
created() {
this.$store.dispatch('action');
}
```
1. When possible, use mutation types instead of hardcoding strings. It will be less error prone.
1. The State will be accessible in all components descending from the use where the store is instantiated.
### Testing Vuex
#### Testing Vuex concerns
Refer to [vuex docs][vuex-testing] regarding testing Actions, Getters and Mutations.
#### Testing components that need a store
Smaller components might use `store` properties to access the data.
In order to write unit tests for those components, we need to include the store and provide the correct state:
```javascript
//component_spec.js
import Vue from 'vue';
import store from './store';
import component from './component.vue'
describe('component', () => {
let vm;
let Component;
beforeEach(() => {
Component = Vue.extend(issueActions);
});
afterEach(() => {
vm.$destroy();
});
it('should show a user', () => {
const user = {
name: 'Foo',
age: '30',
};
// populate the store
store.dipatch('addUser', user);
vm = new Component({
store,
propsData: props,
}).$mount();
});
});
```
[vue-docs]: http://vuejs.org/guide/index.html [vue-docs]: http://vuejs.org/guide/index.html
[issue-boards]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/app/assets/javascripts/boards [issue-boards]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/app/assets/javascripts/boards
[environments-table]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/app/assets/javascripts/environments [environments-table]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/app/assets/javascripts/environments
...@@ -493,3 +774,7 @@ new Component().$mount(); ...@@ -493,3 +774,7 @@ new Component().$mount();
[vue-test]: https://vuejs.org/v2/guide/unit-testing.html [vue-test]: https://vuejs.org/v2/guide/unit-testing.html
[issue-boards-service]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/boards/services/board_service.js.es6 [issue-boards-service]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/boards/services/board_service.js.es6
[flux]: https://facebook.github.io/flux [flux]: https://facebook.github.io/flux
[vuex-docs]: https://vuex.vuejs.org
[vuex-structure]: https://vuex.vuejs.org/en/structure.html
[vuex-mutations]: https://vuex.vuejs.org/en/mutations.html
[vuex-testing]: https://vuex.vuejs.org/en/testing.html
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