I have a fairly simple component based question.
If I had 5 components and I click open on one, how can I tell the other 4 that they need to be closed?
To begin with I have put
this.$emit('open');
on the component. Then on the app I have put
#open="closeOthers"
Then in the app I have the following:
'methods':{
closeOthers : function($event){
console.log($event);
}
}
But I'm just logging undefined. How can I
make this not log undefined
update the props on all other components
Full code and demo here >>>
for 1st. You should pass event throw functions. Like this
'toggleSelect' : function(e){
this.$emit('open', e);
this.question.open = !this.question.open;
},
after this. This code will work
'methods':{
closeOthers : function($event){
console.log($event);
}
}
for 2nd. To control open state it is better to move open value to parent and pass it to child.
Full code jsfiddle
Related
I have made some sandbox code of my problem here:
https://codesandbox.io/s/clever-zeh-kdff1z
<template>
<div v-if="started">
<HelloWorld :msg="msg" #exit="exit" #remake="remake" />
</div>
<button v-if="!started" #click="started = !started">start</button>
</template>
<script>
import HelloWorldVue from "./components/HelloWorld.vue";
export default {
name: "App",
components: {
HelloWorld: HelloWorldVue,
},
data() {
return {
started: false,
msg: "Hello Vue 3 in CodeSandbox!",
};
},
methods: {
exit() {
this.started = false;
},
remake() {
this.msg = this.msg + 1;
//this code should recreate our child but...
this.exit();
this.started = true;
// setTimeout(() => {
// this.started = true;
// });
},
},
};
</script>
So! We have 2 components parent and child. The idea is simple - we have a flag variable in our parent. We have a v-if statement for this - hide / show an element depend on the flag value "false" or "true". After we toggle the flag - the child component should be recreated. This is the idea. Simple.
In our parent we have a button which will set the flag variable to "true" and our child will be created and will appear on our page.
Ok. Now we have 2 buttons inside our child.
One button is "exit" which is emit an event so the flag variable of parent will set to "false" and the elemint will disappear from our page(It will be destroyed btw). Works as charm. Ok.
The second button "remake". It emit event so the flag variable will be just toggled (off then on). Simple. We set to "false", we set to "true". So the current child should dissapear, and then imediatly will be created new one.
But here we are facing the problem! Ok, current child is still here, there is no any recreation, it just updates current one... So in child I have checked our lifecycle hooks - created and unmounted via console.log function. And the second button dont trigger them. Start->Exit->Start != Start->Remake.
So can anyone please explain me why this is happening? I cant figure it out.
Interesting thing, if you can see there is some asynchronous code commented in my demo. If we set our flag to "true" inside the async function the child will be recreated and we will see the created hook message but it seems like crutch. We also can add a :key to our component and update it to force rerender, but it also seems like a crutch.
Any explanations on this topic how things work would be nice.
Vue re-uses elements and components whenever it can. It will also only rerender once per tick. The length of a 'tick' is not something you should worry yourself about too much, other than that it exists. In your case the this.exit() and this.started = true statements are executed within the same tick. The data stored in this.started is both true in the last tick and the current tick as it does not end the tick in between the statements, and so nothing happens to your component.
In general you should think in states in Vue rather than in lifecycles. Or in other words: What are the different situations this component must be able to handle and how do you switch between those states. Rather than determining what to do in which point in time. Using :key="keyName" is indeed generally a crutch, as is using import { nextTick } from 'vue'; and using that to get some cadence of states to happen, as is using a setTimeout to get some code to execute after the current tick. The nasty part of setTimeout is also that it can execute code on a component that is already destroyed. It can sometimes help with animations though.
In my experience when people try to use lifecycle hooks they would rather have something happen when one of the props change. For example when a prop id on the child component changes you want to load data from the api to populate some fields. To get this to work use an immediate watcher instead:
watch: {
id: {
handler(newId, oldId) {
this.populateFromApi(newId);
},
immediate: true
}
}
Now it will call the watcher on component creation, and call it afterwards when you pass a different id. It will also help you gracefully handle cases where the component is created with a undefined or null value in one of the props you expect. Instead of throwing an error you just render nothing until the prop is valid.
I am having an issue where when I change a component in my app, many unrelated components seem to be rerendering too. When I use the Vue performance timings config, I see something like (all in the span of about 200ms)
I am trying to figure out what causes these components to rerender. I saw a tip about how to tell the cause of a rerender, but when I put this snippet* in all the rerendering components, I don’t get anything logged to the console.
So, how can I find what is causing all these components to rerender?
*The code I actually put looks like
public mounted() {
let oldData = JSON.parse(JSON.stringify(this.$data));
this.$watch(() => this.$data, (newData) => {
console.log(diff(oldData, newData));
oldData = JSON.parse(JSON.stringify(newData));
}, {
deep: true,
});
}
Using the F12 dev tools in Chrome, you can track down what is triggering your component to re-render. Add an updated hook to your component as below:
updated() {
if (!this.updateCnt)
this.updateCnt = 1;
if (this.updateCnt > 1) { // set to desired
debugger;
}
console.log(`Updated ${this.updateCnt++} times`);
}
}
Refresh your page in Chrome with F12 tools open and wait for breakpoint to be hit. In the Sources tab, you will see the call stack on the right, with your updated() function as the current stack frame. Look back up the call stack and eventually you should see the code that caused the update to trigger. In my case, it was reactiveSetter() in the vue runtime, which was triggered by me setting a property in a parent component.
The code you have above will only trigger if a component's own state changes, not a parent.
I have two components in mu app.vue and i will send data from app.vue to my first component(filter component) at the time of page load.
Now based on the user actions in the displayed data in the second component i need to pass new vales back to the first component.
There i am using a and a . Consider one of the props i receive in the first component is "nselectedOption" and i do this in data: { return { selectedOption: this.nselectedOption }} to avoid mutation warning.
Now everytime i update the values for this component from second component, i am seeing changes in "nselectedOption" only and not in "selectedOption". Can you explain why is that ?
I need the updated value into a v-model of .
1. If i use "nselectedOption" it is updating the textbox but while editing the value throws error.
2. If i use "selectedOption" it is not updating the values in the textbox itself.
I have even tried using the computed values to return the value, it works but if i try to change values in other options in the filter component the already updated values displays null or nothing.
Please help me. Is this problem can be solved using State Management Concept or do i have to have a separate compoenent other than App.Vue to do all this so that it would act as a parent/child kinda thing or is there anyother way to overcome this.
Try using watcher. If you watch for nselectedOption, everytime it changes, the watcher will fire and bind the changed value to selectedOption.
props: ['nselectedOption'],
data: {
selectedOption
},
watch: {
nselectedOption: function (val) {
this.selectedOption = val
}
}
Also, if the prop you are watching is an object/array, consider using spread operator if you want to make a local copy to avoid mutation.
this.someObj = { ...someProp }
I am creating a tab component that loads its v-tab-item components dynamically, given an array of configuration objects that consist of tabName, id, and tabContent which is a resource location for the component. I have it successfully loading the components. However, they don't actually initialize (or run their created() methods) until I switch tabs. I just get empty tabs with the correct labels. Using the DOM inspector initially shows just <componentId></componentId>, and then when I switch tabs, those tags are replaced with all of the component's content.
How do I get the dynamic components to initialize as soon as they are loaded?
EDIT: I created a CodePen here:
https://codepen.io/sgarfio/project/editor/DKgQON
But as this is my first CodePen, I haven't yet figured out how to reference other files in the project (i.e. what to set tabContent to so that require.js can load them up). I'm seeing "Access is denied" in the console, which makes it sound like it found the files but isn't allowed to access them, which is weird because all the files belong to the same project. So my CodePen doesn't even work as well as my actual project. But maybe it will help someone understand what I'm trying to do.
Also, after poking around a bit more, I found this:
http://michaelnthiessen.com/force-re-render/
that says I should change the key on the component and that will force the component to re-render. I also found this:
https://v2.vuejs.org/v2/guide/components-dynamic-async.html
Which has a pretty good example of what I'm trying to do, but it doesn't force the async component to initialize in the first place. That's what I need the async components to do - they don't initialize until I switch tabs. In fact they don't even show up in the network calls. Vue is simply generating a placeholder for them.
I got it working! What I ended up doing was to emit an event from the code that loads the async components to indicate that that component was loaded. The listener for that event keeps a count of how many components have been loaded (it already knows how many there should be), and as soon as it receives the right number of these events, it changes the value of this.active (v-model value for the v-tabs component, which indicates which tab is currently active) to "0". I tried this because as I noted before, the async components were loading/rendering whenever I switched tabs. I also have prev/next buttons to set this.active, and today I noticed that if I used the "next" button instead of clicking on a tab, it would load the async components but not advance the tab. I had already figured out how to emit an event from the loading code, so all I had to do at that point was capture the number of loaded components and then manipulate this.active.
I might try to update my CodePen to reflect this, and if I do I'll come back and comment accordingly. For now, here's a sample of what I ended up with. I'm still adding things to make it more robust (e.g. in case the configuration object contains a non-existent component URL), but this is the basic gist of it.
created: function() {
this.$on("componentLoaded", () => {
this.numTabsInitialized++;
if(this.numTabsInitialized == this.numTabs) {
// All tabs loaded; update active to force them to load
this.active = "0";
}
})
},
methods: {
loadComponent: function(config) {
var id = config.id;
var compPath = config.tabContent;
var self = this;
require([compPath], function(comp) {
Vue.component(id, comp);
self.$emit("componentLoaded");
});
}
}
Here is the example:
http://jsfiddle.net/hulufei/twr4thuh/7/
It just worked when bind onClick in virtual dom(like line 18), but If I comment line 18 and comment off line 8 to bind click with addEventListener, it failed.
So what's the problem?
TestUtils triggers events within react's synthetic event system, so the native event that addEventListener listens for is never going to be triggered. You will need to use the native click method on the element in your test:
var events = Events();
ReactTestUtils.renderIntoDocument(events);
events.refs.button.getDOMNode().click();
events.state.event.should.equal('click');
Additionally, you've misspelled clickHandler in your addEventListener definition.
jsfiddle
You can also simplify adding your event listener by reusing your prop definition:
componentDidMount: function () {
this.refs.button.getDOMNode().addEventListener('click', this.clickHandler);
},
Note:
Is there a reason why you want to use addEventListener instead of just passing an onClick attribute for your button? Unless there's a specific and good reason otherwise, i'd suggest doing things the react way when handling events for sanity :)
Edit
I originally mentioned that I did not know what TestUtils' SimulateNative.click did not trigger the event. I was wrong in thinking that it ever would since it would be simulating a native click event within the react even system. #thilo pointed me in the right direction :)
I had many problems while testing addEventListener, and I got the following conclusion.
You can create the events listener with pure javascript, jquery, but when running the tests with Jest I always had a problem.
The rendering of ReactTestUtils does not work directly with the document, and when we do:
For example, our events were added in the document, when rendering with ReactTestUtils it creates a div and renders it in the div, This way I could not get Simulate to trigger the call.
My first solution was to use jquery to create the listener and to test I did the render manually by appending the div in document.body, and triggered the events with the dispachEvent of javascript. But I thought the code was dirty, not the best way to work.
I made a sample code by adding the event and testing it with Jest, also have a test teaching to get all the listener that were created.
You can find the code here: https://github.com/LVCarnevalli/create-react-app/tree/master/src/components/datepicker
Component:
componentDidMount() {
ReactDOM.findDOMNode(this.datePicker.refs.input).addEventListener("change", (event) => {
const value = event.target.value;
this.handleChange(Moment(value).toISOString(), value);
});
}
Test:
it('change empty value date picker', () => {
const app = ReactTestUtils.renderIntoDocument(<Datepicker />);
const datePicker = ReactDOM.findDOMNode(app.datePicker.refs.input);
const value = "";
const event = new Event("change");
datePicker.value = value;
datePicker.dispatchEvent(event);
expect(app.state.formattedValue).toEqual(value);
});
Links:
window.addEventListener not triggered by simulated events: https://github.com/airbnb/enzyme/issues/426
Creating and triggering events: https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events