How can i destroy this watcher? I need it only one time in my child component, when my async data has loaded from the parent component.
export default {
...
watch: {
data: function(){
this.sortBy();
},
},
...
}
gregor ;)
If you construct a watcher dynamically by calling vm.$watch function, it returns a function that may be called at a later point in time to disable (remove) that particular watcher.
Don't put the watcher statically in the component, as in your code, but do something like:
created() {
var unwatch = this.$watch(....)
// now the watcher is watching and you can disable it
// by calling unwatch() somewhere else;
// you can store the unwatch function to a variable in the data
// or whatever suits you best
}
More thorough explanation may be found from here: https://codingexplained.com/coding/front-end/vue-js/adding-removing-watchers-dynamically
Here is an example:
<script>
export default {
data() {
return {
employee: {
teams: []
},
employeeTeamsWatcher: null,
};
},
created() {
this.employeeTeamsWatcher = this.$watch('employee.teams', (newVal, oldVal) => {
this.setActiveTeamTabName();
});
},
methods: {
setActiveTeamTabName() {
if (this.employee.teams.length) {
// once you got your desired condition satisfied then unwatch by calling:
this.employeeTeamsWatcher();
}
},
},
};
</script>
If you are using vue2 using the composition-api plugin or vue3, you can use WatchStopHandle which is returned by watch e.g.:
const x = ref(0);
setInterval(() => {
x.value++;
}, 1000);
const unwatch = watch(
() => x.value,
() => {
console.log(x.value);
x.value++;
// stop watch:
if (x.value > 3) unwatch();
}
);
For this kind of stuff, you can investigate the type declaration of the API, which is very helpful, just hover the mouse on it, and it will show you a hint about what you can do:
Related
Mey be it is simple, but I'm new in frontend. I have a page component. And I need to fetch data before component calculated.
import {mapActions, mapGetters} from 'vuex'
export default {
name: "notFoundPage",
methods: {
...mapActions([
'GET_SUBCATEGORIES_FROM_CATEGORIES'
]),
},
computed: {
...mapGetters([
'SUBCATEGORIES'
]),
subCategories() {
// doing some calculations with already updated SUBCATEGORIES in store
}
return result;
}
},
created() {
this.GET_SUBCATEGORIES_FROM_CATEGORIES()
> **// from here we go to store**
},
mounted() {
this.GET_SUBCATEGORIES_FROM_CATEGORIES()
}
}
store:
let store = new Vuex.Store({
state: {
categories: [],
subcategories: []
},
mutations: {
SET_CATEGORIES_TO_STATE: (state, categories) => {
state.categories = categories;
},
SET_SUBCATEGORIES_TO_STATE: (state, subcategories) => {
state.subcategories = subcategories;
}
},
actions: {
GET_CATEGORIES_FROM_API({commit}) {
return axios('http://localhost:3000/categories',
{
method: "GET"
})
But here compiler returns to component. I do not have any idea, why it is not finishing this action. And after calculating the computed block in component it returns to this point. But I need 'SET_CATEGORIES_TO_STATE' already updated
.then((categories) => {
commit('SET_CATEGORIES_TO_STATE', categories.data)
return categories;
}).catch((error) => {
console.log(error);
return error;
})
},
GET_SUBCATEGORIES_FROM_CATEGORIES({commit}) {
this.dispatch('GET_CATEGORIES_FROM_API').then(categories => {
let subs = categories.data.map(function(category) {
return category.subcategories.map(function(subcategory) {
return subcategory.name
})
})
commit('SET_SUBCATEGORIES_TO_STATE', subs)
return subs
})
}
},
getters: {
CATEGORIES(state) {
return state.categories;
},
SUBCATEGORIES(state) {
return state.subcategories;
}
}
if you have difficulties with timings and async tasks, why don't you use async/await?
you want to wait in a async function (for example calling a backend for data) till the data is fetched. then you want to manipulate/delete/change/add, do what ever you want with that data and display the result on screen.
the point is, Vue is a reactive Framework, which means it rerenders (if the setup is correct made) the content by itself after what ever calculation is finished. so don't worry about something like that.
to be honest, the question is asked really weird. and your code is hard to read. sometimes moving two steps back and try a other way isn't false as well.
In my parent component:
<UsersList :current-room="current_room" />
In the child component:
export default {
props: {
currentRoom: Object
},
data () {
return {
users: []
}
},
mounted () {
this.$nextTick( async () => {
console.log(this.currentRoom) // this, weirdly, has the data I expect, and id is set to 1
let url = `${process.env.VUE_APP_API_URL}/chat_room/${this.currentRoom.id}/users`
console.log(url) // the result: /api/chat_room/undefined/users
let response = await this.axios.get(url)
this.users = response.data
})
},
}
When I look at the page using vue-devtools, I can see the data appears:
I've run into this issue in the past – as have many others. For whatever reason, you can't rely on props being available in the component's mounted handler. I think it has to do with the point at which mounted() is called within Vue's lifecycle.
I solved my problem by watching the prop and moving my logic from mounted to the watch handler. In your case, you could watch the currentRoom property, and make your api call in the handler:
export default {
props: {
currentRoom: Object
},
data() {
return {
users: []
}
},
watch: {
currentRoom(room) {
this.$nextTick(async() => {
let url = `${process.env.VUE_APP_API_URL}/chat_room/${room.id}/users`
let response = await this.axios.get(url)
this.users = response.data
})
}
},
}
I don't think you really need to use $nextTick() here, but I left it as you had it. You could try taking that out to simplify the code.
By the way, the reason console.log(this.currentRoom); shows you the room ID is because when you pass an object to console.log(), it binds to that object until it is read. So even though the room ID is not available when console.log() is called, it becomes available before you see the result in the console.
I have a Vuex state that holds a user ID. In my component's mounted(), I try to use that user ID, but it's always null.
How do I get the state from my computed mapGetters into my mounted()?
Here's my computed:
computed: {
...mapGetters('auth', [
'userid'
])
}
And here's my mounted():
mounted () {
HTTP.get('account/' + this.userid + '/')
.then((response) => {
this.account = response.data
})
}
The this.userid is always null.
BTW when I look at the Vue inspector, the auth/userid has the correct value in the getter auth/userid. How do I access auth.userid from mounted()?
userid might not be available at the time component is mounted. You can fix it by watching userid value, and only call HTTP request when userid is changed and available:
computed: {
...mapGetters('auth', [
'userid'
])
},
watch: {
'userid': {
handler (newVal) {
if (newVal) { // check if userid is available
this.getAccountInformation()
}
},
immediate: true // make this watch function is called when component created
}
},
methods: {
getAccountInformation () {
HTTP.get('account/' + this.userid + '/')
.then((response) => {
this.account = response.data
})
}
}
DEBUG
To debug this, first skip the mapGetters, and even getters, and return your state directly.
For example.
computed:{
userId() { return this.$store.state.auth.userid }
}
I don't know how your store or modules are set up, so you might have to change things a bit.
Once that works, add it to your getters and use this.$store.getters.userid, or such.
Finally, when that works, try your original mapGetters and double check your module alias.
POSSIBLE ASYNC ISSUE
Now, on the other hand, if your getter is async, you will also get a null, before the userid promise resolves. You would have to use an asyncComputed, or wait for the result in your mounted.
I would like to assign setter methods via mapState. I currently use a workaround where I name the variable that I am interested in (todo) as a temporary name (storetodo) and then refer to it in another computed variable todo.
methods: {
...mapMutations([
'clearTodo',
'updateTodo'
])
},
computed: {
...mapState({
storetodo: state => state.todos.todo
}),
todo: {
get () { return this.storetodo},
set (value) { this.updateTodo(value) }
}
}
I would like to skip the extra step and define the getter, setter directly within mapState.
Why would I want to do this?
The normal approach would be use mapMutations/mapActions & mapState/mapGetters
without the computed get/set combination that I have illustrated above and to reference the mutation directly in the HTML:
<input v-model='todo' v-on:keyup.stop='updateTodo($event.target.value)' />
The getter/setter version allows me to simply write:
<input v-model='todo' />
You can't use a getter/setter format in the mapState
what you can try is directly return the state in your get() and remove mapState from the computed property
computed: {
todo: {
get () { return this.$store.state.todos.todo},
set (value) { this.updateTodo(value) }
}
}
Here is a related but not same JsFiddle example
This is my current workaround. Copied from my personal working project
// in some utils/vuex.js file
export const mapSetter = (state, setters = {}) => (
Object.keys(state).reduce((acc, stateName) => {
acc[stateName] = {
get: state[stateName],
};
// check if setter exists
if (setters[stateName]) {
acc[stateName].set = setters[stateName];
}
return acc;
}, {})
);
In your component.vue file
import { mapSetter } from 'path/to/utils/vuex.js';
export default {
name: 'ComponentName',
computed: {
...mapSetter(
mapState({
result: ({ ITEMS }) => ITEMS.result,
total: ({ ITEMS }) => ITEMS.total,
current: ({ ITEMS }) => ITEMS.page,
limit: ({ ITEMS }) => ITEMS.limit,
}),
{
limit(payload) {
this.$store.dispatch({ type: TYPES.SET_LIMIT, payload });
},
},
)
},
}
now you can use the v-model bindings. l
Another way of approaching that is using store mutations like below:
//in your component js file:
this.$store.commit('setStoretodo', storetodo)
Assuming you define setStoretodo in mutations of your vuex store instance (which is something recommended to have anyways):
//in your vuex store js file:
state:{...},
actions: {...}
...
mutations: {
setStoretodo(state, val){
state.storetodo = val
},
...
}
...
That keeps the property reactive as mapState will grab the updated value and it will be rendered automatically.
Surely, that's not as cool as just writing this.storetodo = newValue, but maybe someone will find that helpful as well.
I have a fairly heavy component which I would like to load asynchronously, while at the same time showing the user a loading spinner when it's loading.
This is my first attempt, using loading defined in data linked to a spinner component with v-if="loading". Unfortunately this doesn't work because it seems that Vue doesn't rebind this properly for functions inside components -
export default {
data: {
return {
loading: false,
};
},
components: {
// ...
ExampleComponent: (resolve) => {
// Doesn't work - 'this' is undefined here
this.loading = true;
require(['./ExampleComponent'], (component) => {
this.loading = false;
resolve(component);
});
},
},
};
I've also found some Vue 1.0 examples, but they depended on $refs - in 2.0 $refs is no longer reactive, and cannot be used for this. The only way left is for the child component itself to do something on its mount lifecycle event to the application data state to remove the loading spinner, but that seems a bit heavy. Is there a better way to do this?
You could declare a variable outside the object scope (but still is within module scope) then use the created hook to attach this. So your updated code would look like:
let vm = {}
export default {
// add this hook
created () {
vm = this;
},
data: {
return {
loading: false,
};
},
components: {
// ...
ExampleComponent: (resolve) => {
// since 'this' doesn't work, we reference outside 'vm'
vm.loading = true;
require(['./ExampleComponent'], (component) => {
vm.loading = false;
resolve(component);
});
},
},
};