I have a parent component that has a button when the user clicks it will make a request and passed the data into a child component (a ngx-bootstrap modal). The child component will use the async data to make another request to render its UI.
My parent component is like this:
<Parent>
<child-modal [subSectionInfo]="subSectionInfo"></child-modal>
</Parent>
the subSectionInfo is async data retrieved from an ajax in Parent component.
My child component will make call like this:
ngOnInit() {
const id = this.subSectionInfo.id;
this._fetchData(id)
}
private _fetchData(id: number) {
this.service
.getData(id).pipe(
.subscribe((data: any) => {
this.list = data;
});
}
However, this always gives me undefined which causes the child component ajax call failed. Is any way to solve this issue? Thank you so much in advance!
Currently, your code does not wait on the first request to complete. While the request for subSectionInfo is being made in the parent component, it's value is undefined since the value hasn't returned from the server yet. This is why the child component get's undefined. There are 2 ways to approach this.
In your parent component, you can wait until the data is loaded and then pass in subSectionInfo to your child component.
In your child component, you can make use of the ngOnChanges life-cycle hook. This is where your child component implements OnChanges. You can read more about it here.
ngOnChanges(changes: SimpleChanges) {
if (changes['subSectionInfo'].currentValue !== undefined) {
const id = this.subSectionInfo.id;
this._fetchData(id)
}
}
private _fetchData(id: number) {
this.service
.getData(id).pipe(
.subscribe((data: any) => {
this.list = data;
});
}
Hope this helps
Related
I have an app that has a Parent component (app.js) and 2 child sibling components ( Modal.vue and Cart.vue).
I am getting a response back from a call within Modal.vue that needs to trigger a function within Cart.vue right after. What are the best options of going about this?
I don't currently use Vuex, which I know would make this easier.
You can use refs like so:
<parent>
<modal #triggerFunc="triggerFunc"/>
<cart ref="$cartRef"/>
</parent>
...
triggerFunc(){
this.$refs.$cartRef.functionIwantToTrigger()
}
You could create an event bus:
https://www.digitalocean.com/community/tutorials/vuejs-global-event-bus
You can use Custom Events for this using the root Vue instance of the current component tree.
In Modal.vue:
Where you are getting a response back from a call, simply emit a custom event like:
this.$root.$emit('onupdate', data);
In Cart.vue:
Simply listen to this root emitted event like
var vm = new Vue({
data: {},
mounted() {
this.$root.$on('onupdate', data => {
// trigger a function within Cart.vue
this.myFunction(data)
});
}
methods: {
myFunction: function(data) {
console.log(data);
}
}
})
I created the child using:
const ComponentClass = Vue.extend(someComponent);
const instance = new ComponentClass({
propsData: { prop: this.value }
})
instance.$mount();
this.$refs.container.appendChild(instance.$el);
When this.value is updated in the parent, its value doesn't change in the child. I've tried to watch it but it didn't work.
Update:
There's an easier way to achieve this:
create a <div>
append it to your $refs.container
create a new Vue instance and .$mount() it in the div
set the div instance's data to whatever you want to bind dynamically, getting values from the parent
provide the props to the mounted component from the div's data, through render function
methods: {
addComponent() {
const div = document.createElement("div");
this.$refs.container.appendChild(div);
new Vue({
components: { Test },
data: this.$data,
render: h => h("test", {
props: {
message: this.msg
}
})
}).$mount(div);
}
}
Important note: this in this.$data refers the parent (the component which has the addComponent method), while this inside render refers new Vue()'s instance. So, the chain of reactivity is: parent.$data > new Vue().$data > new Vue().render => Test.props. I had numerous attempts at bypassing the new Vue() step and passing a Test component directly, but haven't found a way yet. I'm pretty sure it's possible, though, although the solution above achieves it in practice, because the <div> in which new Vue() renders gets replaced by its template, which is the Test component. So, in practice, Test is a direct ancestor of $refs.container. But in reality, it passes through an extra instance of Vue, used for binding.
Obviously, if you don't want to add a new child component to the container each time the method is called, you can ditch the div placeholder and simply .$mount(this.$refs.container), but by doing so you will replace the existing child each subsequent time you call the method.
See it working here: https://codesandbox.io/s/nifty-dhawan-9ed2l?file=/src/components/HelloWorld.vue
However, unlike the method below, you can't override data props of the child with values from parent dynamically. But, if you think about it, that's the way data should work, so just use props for whatever you want bound.
Initial answer:
Here's a function I've used over multiple projects, mostly for creating programmatic components for mapbox popups and markers, but also useful for creating components without actually adding them to DOM, for various purposes.
import Vue from "vue";
// import store from "./store";
export function addProgrammaticComponent(parent, component, dataFn, componentOptions) {
const ComponentClass = Vue.extend(component);
const initData = dataFn() || {};
const data = {};
const propsData = {};
const propKeys = Object.keys(ComponentClass.options.props || {});
Object.keys(initData).forEach(key => {
if (propKeys.includes(key)) {
propsData[key] = initData[key];
} else {
data[key] = initData[key];
}
});
const instance = new ComponentClass({
// store,
data,
propsData,
...componentOptions
});
instance.$mount(document.createElement("div"));
const dataSetter = data => {
Object.keys(data).forEach(key => {
instance[key] = data[key];
});
};
const unwatch = parent.$watch(dataFn || {}, dataSetter);
return {
instance,
update: () => dataSetter(dataFn ? dataFn() : {}),
dispose: () => {
unwatch();
instance.$destroy();
}
};
}
componentOptions is to provide any custom (one-off) functionality to the new instance (i.e.: mounted(), watchers, computed, store, you name it...).
I've set up a demo here: https://codesandbox.io/s/gifted-mestorf-297xx?file=/src/components/HelloWorld.vue
Notice I'm not doing the appendChild in the function purposefully, as in some cases I want to use the instance without adding it to DOM. The regular usage is:
const component = addProgrammaticComponent(this, SomeComponent, dataFn);
this.$el.appendChild(component.instance.$el);
Depending on what your dynamic component does, you might want to call .dispose() on it in parent's beforeDestroy(). If you don't, beforeDestroy() on child never gets called.
Probably the coolest part about it all is you don't actually need to append the child to the parent's DOM (it can be placed anywhere in DOM and the child will still respond to any changes of the parent, like it would if it was an actual descendant). Their "link" is programmatic, through dataFn.
Obviously, this opens the door to a bunch of potential problems, especially around destroying the parent without destroying the child. So you need be very careful and thorough about this type of cleanup. You either register each dynamic component into a property of the parent and .dispose() all of them in the parent's beforeDestroy() or give them a particular selector and sweep the entire DOM clean before destroying the parent.
Another interesting note is that in Vue 3 all of the above will no longer be necessary, as most of the core Vue functionality (reactivity, computed, hooks, listeners) is now exposed and reusable as is, so you won't have to $mount a component in order to have access to its "magic".
I have two vue files, app.vue and logincomponent.vue.
I use logincomponent.vue to make template that does login box and uses scripts to communicate with go backend in wails, the code itself works, but I'm trying to change value in main app.vue but i cant get it working.
The question is:
"How do I change value of variable in main vue app from component?"
Import:
import LoginScreen from "./components/LoginScreen.vue"
Variable:
data: () => ({
drawer: false,
currentScreenID: 0,
logged: false
Setter:
sendLogin: function () {
var self = this;
if (this.$refs.login_form.validate()) {
self.dialog = true;
self.loadingCircleLogin = true;
self.login_dialog_title = self.login_dialog_logging_title;
window.backend.sendLoginToBackend(self.email, self.password, self.remember_email).then(result => {
if (result === false) {
self.loadingCircleLogin = false;
self.loginFailText = true;
self.login_dialog_title = self.login_dialog_error_title;
} else {
self.dialog = false;
self.currentScreenID = 3;
}
})
}
},
The short answer to if the state of the parent component (or main Vue instance) can be changed from a child component, is no or at least it should not be done. It's an anti-pattern and can produce bugs in your code.
But you have two choices here.
To emit an event from child component, and handling it from parent. So the parent is responsible of changing its own state with its own logic.
When you need to change a value from the main instance from a child component, you emit the event, even with a value you can pass to the emit function, and you program your main instance to listen that event and respond accordingly.
More info here: listening to child component events.
To add a Vuex store to your app. In this way you abstract the state of the app that's common to several components. So your child component could ask the store to change certain state.
More info here: Vuex
Using Vuex is more complex dough, if your app is simple I'd go with first option.
I am using a date picker component library and i want to watch when a property of that component changes.
I have tried this:
watch: {
'$refs.picker.popupVisible': {
handler (new_value) {
console.log('executed')
},
deep: true
}
}
Also this:
computed: {
picker () {
console.log(this.$refs.picker.popupVisible)
return this.$refs.picker.popupVisible
}
}
I know that the solution will be a vue.js hack because this is not the right way.If i had access to child component i would emit en event to parent but unfortunately i don't have.
I had a similar problem using a library which had some limitations.
Unfortunately, your watcher will not work.You have to use the function watcher to make this to work.And you have to use it inside the mounted hook.
mounted() {
this.$watch(
"$refs.picker.popupVisible",
(new_value, old_value) => {
//execute your code here
}
);
}
I also have an example. Please take a look here
What you can do is create a data object in parent component and include the date field in that data object and pass that data object to child component as props
<child :dateObj="dateObj"></child>
data: {
dateObj: {
date: ""
}
}
And in child component you can use the date field of that dateObj props. This is possible because Vue doesn't watch the property of Objects passed as props and we can modify them without Vue complaining in console.
Thus the changed date field is reflected in parent as well.
as title, how can I do that
from offical documentation just tell us that $delete can use argument 'object' and 'key'
but I want delete a component by itself like this
this.$delete(this)
I couldn't find instructions on completely removing a Vue instance, so here's what I wound up with:
module.exports = {
...
methods: {
close () {
// destroy the vue listeners, etc
this.$destroy();
// remove the element from the DOM
this.$el.parentNode.removeChild(this.$el);
}
}
};
Vue 3 is basically the same, but you'd use root from the context argument:
export default {
setup(props, { root }){
const close = () => {
root.$destroy();
root.$el.parentNode.removeChild(root.$el);
};
return { close };
}
}
In both Vue 2 and Vue 3 you can use the instance you created:
const instance = new Vue({ ... });
...
instance.$destroy();
instance.$el.parentNode.removeChild(instance.$el);
No, you will not be able to delete a component directly. The parent component will have to use v-if to remove the child component from the DOM.
Ref: https://v2.vuejs.org/v2/api/#v-if
Quoted from docs:
Conditionally render the element based on the truthy-ness of the expression value. The element and its contained directives / components are destroyed and re-constructed during toggles.
If the child component is created as part of some data object on parent, you will have to send an event to parent via $emit, modify (or remove) the data and the child component will go away on its own. There was another question on this recently: Delete a Vue child component
You could use the beforeDestroy method on the component and make it remove itself from the DOM.
beforeDestroy () {
this.$root.$el.parentNode.removeChild(this.$root.$el)
},
If you just need to re-render the component entirely you could bind a changing key value to the component <MyComponent v-bind:key="some.changing.falue.from.a.viewmodel"/>
So as the key value changes Vue will destroy and re-render your component.
Taken from here