According to the official vue.js documentation, component data must be a function.
In my situation, i want to get data with an axios call and store this data in a component.
The problem is, if a declare this data as a function as the documentation advice to, every time i will need this component it will do a new axios call.
My main goal using vue-components was to minimize axios calls by re-using components-data through my vues, to improve performance.
Am i wrong to use vue-components in this situation?
EDIT: here's some code to clarify my question:
What the documentation recommend to do (data is a function which returns data, which means it will do the axios call everytime you want to use the data i guess.):
Vue.component('user-infos', {
data() {
userInfos = axios.get('ajax/getInfosFiche.php?action=UserInformations')
}
});
What i did (data is an object, which means if multiple vues use it and one modify the data, it will be modified for all the vues) :
Vue.component('user-infos', {
data: {
userInfos = axios.get('ajax/getInfosFiche.php?action=UserInformations')
}
});
What you need is a data store, that holds your data and can be used from different components.
You could for example take a look at VueX.
Another way is to define your own custom store, which does not need to be as heavy as VueX.
One way to do this is create and export an observable object and import it from the components that need to have access to the store.
The way I am currently using it is by making the store object available through a global mixin. That way, every component has access to "this.$store" which holds my data.
const state = Vue.observable({ data: {} });
Vue.mixin({
computed: {
$store: {
get: function() {
return state.data;
},
set: function(newData) {
state.data = newData;
}
}
}
});
You can see the full example here.
Example Implementation
Related
I have a Pinia store with an object "objData", which holds one or more objects, with some additional metadata, which ends up becoming a fairly long variable. It has to be used in quite a number of places, therefore I made a "shortcut" variable instead to the "data" property. However, this shortcut fails to be reactive, whereas the variable i'm pointing to is reactive.
The Pinia object looks like:
objData: {
"fruit": {
data: {...},
...
},
"candy": {
data: {...},
...
},
}
The setup-function:
setup() {
const myStore = useMyStore()
// const fruit = myStore.objData['fruit'].data // <- direct, doesn't work
// const fruit = reactive(myStore.objData['fruit'].data) // <- reactive, doesn't work
const fruit = computed(() => myStore.objData['fruit'].data) // works
return {
myStore,
fruit,
}
}
The data change: (I'm sure I don't need to both do reactive() and refs(), or any at all, but I've tried all kinds of things to get reactivity in my shortcut). This happens in a composable that has access to the store.
if (!("fruit" in store.objData)) {
set(myStore.objData, "fruit", reactive({
data: ref(null),
}))
}
set(myStore.objData["fruit"], 'data', objNewData)
The page:
<div>
{{myStore.objData['fruits'].data.fruit_name}} OK
{{fruit.fruit_name}} OK, if computed(), otherwise not reactive
</div>
Unless I'm using a computed, I only get the inital value, which doesn't get updated when the store updates.
Is it actually bad/expensive/wrong to use a computed() to have a reactive data object in the page in this way? It "feels" wrong, but other than that I have no arguments against it.
(Why) is it not possible to simply make a variable by reference to a reactive variable, I always thought you're just pointing to a memory address.
I'm struggeling to provide an example, as this thing is so deeply integrated in my app. I'm at this point hoping for a glaring mistake on my part, or a simple answer that explains it.
Note 1: I'm using Vue2 with the composition API add-on.
Note 2: This is a very simplified example.
I have a vue.js/nuxt.js component in my UI that displays news based on a backend which can be queried with selectors (e.g. news-type1, news-type2).
I want to add a second instance of that component which uses exactly the same backend, but allows the user to use a few different selectors (e.g. news-type3, news-type4). The UI kinda works dashboard-like. Implementing that distinction in the .vue component file is no problem (just accept some props and display stuff conditionally to the user), but:
How do I reuse the vuex store? The code of the store for the new card stays exactly the same since the same backend is used. But I can't use the same instance of the store because the selectors and the loaded news should be stored per component and should not be shared between them. Surprisingly I haven't been able to find any easy solutions for that in nuxt. I thought this would be a common use case.
MWE for my use case:
/** Vuex store in store/news.js **/
export const state = () => ({
// per default only news-type1 is selected, but not news-type2. the user can change that in the UI
currentSelectors: ['news-type1'],
news = [] // object array containing the fetched news
});
export const mutations = {
// some very simple mutations for the stae
setSelectors (state, data) {
state.currentSelectors = data;
},
setNews (state, data) {
state.news = data;
}
}
export const actions = {
// simplified get and commit function based on the currentSelectors
async loadNews ({ commit, state }) {
const news = await this.$axios.$get(`/api/news/${state.currentSelectors.join(',')}`);
commit('setNews', news);
// ... truncated error handling
},
// Helper action. In comparison to the mutation with the same name, it also calls the load action
async setSelectors ({ commit, dispatch }, selectors) {
commit('setSelectors', selectors);
dispatch('loadNews');
},
};
In my news-card.vue I simply map the two states and call the two actions loadNews (initial load) and setSelectors (after user changes what news to show in the UI). This should stay the same in both instances of the card, it just should go to different store instances.
My current alternative would be to simply copy-paste the store code to a new file store/news-two.js and then using either that store or the original store depending on which prop is passed to my news-card component. For obvious reasons, that would be bad practice. Is there a better complicated alternative that works with nuxt?
All related questions I have found are only for Vue, not for nuxt vuex stores: Need multiple instances of Vuex module for multiple Vue instances or How to re-use component that should use unique vuex store instance.
I'm using vue.js extends for the first time. I have a component that extends another and it needs to read the root components data to update the status in its own component.
What I'm finding is that the component that extends the other only seems to take a copy of the root's data when it's rendered but if I update a property in the root component it's not updated in the extended component.
So I might not be going about this the right way if the extended component doesn't update when the root does. For example I want to check the length of an array on the root component and update another data value. It updates the value on the root but not on the extended component.
Is this the expected behaviour and is there a way I can send the updated data down to the extended component?
Sample code:
<a inline-component>
<input type="text" v-model="myArray" />
<button v-on:click="saveData">Save</button>
</a>
<b inline-component>
<div v-if="myArray.length > 0">On Target</div>
</b>
var a = Vue.component('a', {
data: function () {
return {
myArray: [],
}
},
methods: {
saveData : function(){
var vm = this;
axios.post('/save', {
})
.then(function (response) {
vm.myArray = response.data;
})
.catch(function (error) {
console.log(error);
});
},
}
});
Vue.component('b', {
extends: a,
});
I have a component that extends another and it needs to read the root components data to update the status in its own component.
For the purposes of my answer I'm going to assume that you have two component definitions, A and B, and B extends A. I assume that when you say root you just mean A.
What I'm finding is that the component that extends the other only seems to take a copy of the root's data when it's rendered but if I update a property in the root component it's not updated in the extended component.
Rendering is not really relevant here. The data properties are set up when a component instance is created. Typically rendering will happen just after creation but merging any data happens much earlier in the component life-cycle. Even if the component isn't rendered the data will still be initialised.
No copying takes place. Let's consider a data function on component A:
data () {
return {
myArray: []
}
}
Every time this function is invoked it is going to return a new object, each containing a new array. This is precisely what happens if you create an instance of A directly. For each instance, Vue will call this function and get a new object defining the data. Generally that's what you'd want, rather that having components sharing data.
Now let's consider B. That might define its own data function. When an instance of B is created Vue will call the data function for both A and B and then merge the objects. No copying takes place, just merging. If you want to know more about how Vue handles merging in general see the documentation but for data the strategy is pretty simple. Properties from both objects will be combined with B taking precedence over A if there's a clash of property names. There is no recursive merging of properties.
So the idea of updating 'a property in the root component' is not particularly well-defined. You might be thinking of it as a bit like a prototype chain, where modifying a superclass would impact the subclass, but that isn't what's going on here. The data functions are invoked when the component is created and that's that. There isn't a lasting link back to the component definition like there is with a prototype chain.
If you really want all your component instances to share the same data value then it can be done, you just need to make sure that the data function is returning the same object/array every time. e.g.
const myArray = []
export default {
name: 'A',
data () {
return {
myArray
}
}
}
Written this way all instances of A will share the same array for myArray. So long as B doesn't define it's own value for myArray it will share it too.
For example I want to check the length of an array on the root component and update another data value. It updates the value on the root but not on the extended component.
I'm struggling a bit to understand what that means. It seems there are lots of assumptions about things being shared, single instances here. It's not entirely clear how you update the 'root' given it's a component definition and not a component instance.
If possible you should use a computed property for this. That would be inherited by B. Each instance of A (or B) would have their own value for this computed property, which might be a little wasteful if they're all going to be the same, but it's probably still the best way to go.
You could in theory use a watch. That should be inherited too but keep in mind it would be manipulating values for that particular instance.
Reading between the lines a little, if you wanted to update something on the 'root' so that it magically appeared in the subcomponents you could use the same shared reference-type trickery that I demonstrated earlier for myArray. You may need to be careful with how you update it though. If, for example, you used a watch you might find the you end up updating the same object many times, once for each instance of the component.
Update:
Based on the code you've posted it could be made to work something like this:
var myArray = [];
var a = Vue.component('a', {
data: function () {
return {
myArray: myArray // Note: using the same, shared array
}
},
methods: {
saveData : function(){
var vm = this;
axios.post('/save', {
})
.then(function (response) {
// Note: Updating the array, not replacing it
var myArray = vm.myArray;
myArray.splice(0, myArray.length);
myArray.push.apply(myArray, response.data);
})
.catch(function (error) {
console.log(error);
});
},
}
});
Vue.component('b', {
extends: a,
});
Your example didn't include any ES6 so I've refrained from using it but it would be a bit simpler if that were available.
The example above works by sharing the same array between all instances of the component and then mutating that instance. Assigning a new array to that property won't work as it would only update that particular component instance.
However, all that said, this is increasingly looking like a case where you should give up on trickery and just use the Vuex store instead.
I have one global state with some modules.
now i have vue components for various parts of my page.
i have everything setup so /foo uses the foo store (this works).
the created method loads data from an API and writes it to the store
now i have /foo/bar as another (sibling) component, but it needs to access the same store as /foo, but i can't get it to work.
if i enter /foo/bar/ in the URL, there is nothing in the store.
but if i switch to /foo, and then back to /foo/bar, the data is in the store and being output correctly
I've tried registering /foo/bar as a child, which seemed to have no effect (and actually it's not really a child, but just another page with the same data..)
I also tried
state: {
...mapState([
'foo'
)]
}
in /foo/bar, but that doesn't seem to be the right way either
what is the best practice to
load data from API on created on any of a specified set of pages
access said data on any of those pages (i.e. sharing the same store)
i've tried all day to find a solution, but it seems I didn't understand something.
thanks for your help :)
EDIT
actually, while i read my question again, i think my whole problem is the data not being loaded (because the created method is not called). how can i make sure this happens on any page using the store and just once? i can't just write an api call in every created method, can i?
Well, I think just to summarize your problem could be called like you're not being able to access the same state between two different componentes.
What I do normally is that I make an API call from one component inside the method beforeMount, that will guarantee that once my component is created, the data will be available to be used.
Furthermore, after calling the api, I update my state so after that I can call it from everywhere.
One thing that you have to take care with is which component is loaded first?
If A is B's parent, then you should load data inside A.
However, if A and B are siblings, then you should load data inside both of them because you can access first either Component A or B, then you don't know when the data is going to be available. In that case, I would load the data in both of the components.
Also, add cache to your server so you don't need to load the same data again.
For example:
State
{
data: {}
}
Component A
export default {
name: 'Batch',
beforeMount() {
this.getDataFromAPI();
},
methods: {
// getDataFromAPI will store its return inside data with a mutation
...mapActions(['getDataFromAPI']),
randomMethod() {
// Now I can Use my state
const data = this.$store.state.data;
}
}
};
Component B
export default {
name: 'Batch',
methods: {
randomMethodB() {
// If component A was loaded first than component B and A is B's parent, then the state will be accessible in the same manner and it should be populated
const data = this.$store.state.data;
}
}
};
Actions
const getDataFromAPI = ({ commit }) => new Promise((resolve, reject) => {
// Call server
const data = await callServer();
commit('updateMyStateWithData');
resolve(data);
});
export default {
getDataFromAPI
}
Mutations
const mutations = {
updateMyStateWithData(state, newData) {
state.data = newData;
}
}
export default mutations;
Another thing that I do is to define getters, that way is a good approach to load data once, and inside the getter you update the data to return only the things that your UI needs.
I hope that it helps!
I have a component whose data is initialized by ajax. I know vue.js has provide several lifecycle hooks: Lifecycle-Diagram. But for ajax to initialize the data, which hook(beforeCreate, create, mounted, etc) is the best place to do it:
hook_name: function() {
ajaxCall(function(data) {
me.data = data;
});
}
Currently, i do it in mounted, making it to re-render the component. But i think we should get the data before the first render. Can someone figure out the best way to do it?
If you want to initialize your component with data you receive from a request, created() would be the most appropriate hook to use but it is a request, it might not resolve by the end of created or even mounted() (when even your DOM is ready to show content!).
So do have your component initialized with empty data like:
data () {
return {
listOfItems: [],
someKindOfConfig: {},
orSomeSpecialValue: null
}
}
and assign the actual values when you receive them in your created hook as these empty data properties would be available at that point of time, like:
created () {
someAPICall()
.then(data => {
this.listOfItems = data.listOfItems
})
/**
* Notice the use of arrow functions, without those [this] would
* not have the context of the component.
*/
}
It seems like you aren't using (or aren't planning to use) vuex but I'd highly recommend you to use it for for managing your data in stores. If you use vuex you can have actions which can make these api calls and by using simple getters in your component you would have access to the values returned by the request.