How would you add a component to a View from the ViewModel. For example, I have the following:
I have a service injected into a component. Then from the component I fetch data and when I get the response I set the data property to the fetched data. After this I would like to mount the component to the View with the fetched data as a bindable.
this.service.get()
.then(response => response.json())
.then(data =>{
this.data = data.results
//Mount element to View here: <component data.bind="data"></component>
})
Im asking this question because if I set the value when fetched and on the View to this:
<component data.bind="data"></component>
It passes an empty object. I have tried using the service on the canActivate and activate methods.
Component:
export class Component{
#bindable data
bind(){
console.log(this.data)
}
}
I copied your code in to a gist and ran it on gist.run here: https://gist.run/?id=04907ff8d8b6d8b4aee625669d8571a3
It runs as expected for me. I even updated it to set the data inside a promise.
Now, if you want to be notified when the data property changes, you'll need to implement a function called ${propertyName}Changed(newValue, oldValue) so in this case, dataChanged(newValue, oldValue). I created a separate gist to show how you might want to change your code: https://gist.run/?id=34a01ca3f600470691d5b91c9131f33b
You'll notice in my code I didn't use the newValue and oldValue parameters. I did this on purpose to let you know that Aurelia still sets the property value. The callback is just there to let your code do stuff when the property value changes.
The "data" field being bound to is a field on the ViewModel using your component, not a field in your component.
Related
I am quite new to Vue.js and while developing my first project i have stumbled upon a problem which I think is related to the component's lifecycle.
The context is the following:
I am using Vue 3 with composition API.
I have a "Map" component in which I use d3.js to show a chart.
In my Setup() method I have onBeforeMount() and onMounted().
In onBeforeMount() method, I want to use data from my Firestore database for the values in the chart. The console.log on line 47 shows the data correctly.
In onMounted(), is where I plan to put my d3 chart. But when I try to access the data as in console.log on line 55, I get undefined...
Ideally, from "Map" component, I want to fetch the data from my database and use it in order to create the chart and then have the component render the chart.
Then I would have another component called 'MapSettings" that will be able to alter the data in "Map" such as filters etc...and have the values automatically updated in the chart.
Finally, both components will be siblings and have same parent component. So "Map" and "MapSettings" are on same hierarchical level.
But first I need to understand why I am getting undefined.. Any help or suggestion would be greatly appreciated!
Your lifecycle hooks look nice. The problem that you're facing has to do with code been executed asynchronously and code been executed synchronously.
You're declaring a function that uses async-await feature. This function will be executed asynchronously. In this case, you're getting data from Firestore and storing it in a ref at onBeforeMount().
On the other hand, you're declaring a normal function at onMounted() trying to access a ref's value, which will result in undefined because the function that you define at onBeforeMount() didn't finish its execution (or it's in the event queue) when onMounted is called.
That's why you first see the console.log that comes from onMounted.
One solution would merge both functions in one lifecycle hooks and use async await:
setup() {
const {actorDocs, load} = getActorDocs()
const actorsData = red([])
// load actor data from db
onBeforeMount( async () => {
await load()
actorsData.value = actorDocs
console.log(actorsData.value)
// manipulate it here...
})
}
Keep in mind that you cannot pause with async-await a lifecycle hook. What you're pausing is the function that Vue will execute in that hook. Indeed, this is really nice because pausing a hook wouldn't be efficient at all.
i face that problem, in my case i want use imgsRef.value out of onBeforeMount scope. How to get imgsRef value out of beforeMount scope?
onBeforeMount( async () => {
await axios
.get("http://localhost:3000/ourMoment")
.then((response) => {
imgsRef.value = response.data
// imhsRef get the value from api
console.log(imgsRef.value.photo)
})
})
// i try to concole.log here but the value still empty
console.log(imgsRef.value)
If props are not editable how does one go about adding data relevant to the user interface in a local component?
Say you receive an Array of blog posts, each post can be iterated in the interface with v-for - but each elements also needs a few extra properties only relevant to the interface like "is_active" or "is_expanded".
How does one go about adding these extra properties to each element in the array received from the prop if props should not be modified?
In particular case i am using inertia.js
So the data can not be modified outside of the component that receives the prop - in a Vuex setup one might mutate the data from the backend and prepare it for the interface before going to the component, but this isn't available here.
create a computed property which maps the prop array and adds the extra properties
computed:{
_array(){
return this.propArray.map((item) => {
return {
...item,is_active:false,is_expanded:false
})
}
}
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'm trying to understand the solution in this SO post. The solution allows the user to keep track of the previous route in the current route.
Below is the snippet of Vue code that I'm trying to understand. If I understand correctly, next accepts a callback function that receives the current component's vue instance. We then set the prevRoute data property of this vue instance to from. Is this interpretation correct? If not, what is actually happening?
If someone could also add a brief explanation as to what the Vue API is doing behind the scenes that would also be very helpful for me to actually understand the snippet of code.
...
data() {
return {
...
prevRoute: null
}
},
beforeRouteEnter(to, from, next) {
next(vm => {
vm.prevRoute = from
})
},
...
As per the documentation...
The beforeRouteEnter guard does NOT have access to this, because the guard is called before the navigation is confirmed, thus the new entering component has not even been created yet.
However, you can access the instance by passing a callback to next. The callback will be called when the navigation is confirmed, and the component instance will be passed to the callback as the argument
So vm is the component instance assigned to the destination route.
From your question...
We then set the prevRoute data property of this vue instance to from. Is this interpretation correct?
Almost. All you're doing is setting a direct object property on the Vue component which is after all, just a JavaScript object at heart. For example
const vm = { name: 'I am totally a Vue component' }
vm.prevRoute = from
This property will not be reactive but you can certainly access it within your component via this, just as you can other non-data properties like $el, $refs, etc.
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.