i have a button in my project when i click on it two queries added to URL
onClickBtn(){
this.$router.push({queries: {name:'kevin' , age:21} })
}
and I have a watch on $route
watch:{
$route:function(){
// call API
}
}
and when i click on that button severall time
watch calls my API every time although nothing has changed
and this make a problem form me
because nothing has changed in route But API is called and the same data is
received .
what should I do to avoid calling API in watch , when queries don't changed ??
The object you are pushing on the router is always different, that's why the $route watch is launched.
You can compare the data you receive in the watch, so that when they are different then you invoke the API:
watch:{
'$route' (newRoute, lastRoute){
// Check if query is different
// call API
}
}
On top of the answer that Cristian provided, you could also even double-check if your stuff has changed before even pushing a new object to your router.
Like this
checkIfUpdateNeeded && this.$router.push({queries: {name: 'kevin', age:21 } })
That way, you will have less moving parts and you won't have a trigger in the watcher for "nothing", especially if you're pushing a bigger object and want to make a deep-diff between 2 objects.
Related
I'm working on my first Vue 3 (and therefore vuex 4) app coming from a pretty solid Vue 2 background.
I have an component that is loading data via vuex actions, and then accessing the store via a returned value in setup()
setup() {
const store = useStore();
const fancy = computed(() => store.state.fancy);
return { fancy };
},
fancy here is a deeply nested object, which I think might be important.
I then want to run a function based on whenever than value changes, so I have set up a watch in my mounted() lifecycle hook
watch(
this.fancy,
(newValue) => {
for (const spreadsheet in newValue) {
console.log(Object.keys(newValue[spreadsheet].data))
setTimeout(()=>{
console.log(Object.keys(newValue[spreadsheet].data))
},500)
...
I tried using the new onMounted() hook in setup and watchEffect and store.watch instead, but I could not get watch/watchEffect to reliably trigger in the onMounted hook, and watchEffect never seemed to update based on my computed store value. If you have insight into this, that would be handy.
My real issue though is that my watcher gets called seemingly before the value is updated. For instance my code logs out [] for the first set of keys, and then a half second later a full array. If it was some kind of progressive filling in of the data, then I would have expected the watcher to be called again, with a new newValue. I have also tried. all the permutations of flush, deep, and immediate on my watcher to no avail. nextTick()s also did not work. I think this must be related to my lack of understanding in the new reactivity changes, but I'm unsure how to get around it and adding in a random delay in my app seems obviously wrong.
Thank you.
I have a call in my created method which has an await.
I want to know that the results of that call are loaded so that i can conditionally show/hide things in the DOM.
Right now it looks like the DOM is being rendered before that method has completed. But I though that methods in created were called before the DOM rendered?
You're correct in assuming that the created hook runs before the component mounts. However, the lifecycle hooks are not waiting for async calls to complete. If you want to wait for that call to be completed and data to load, you can do so by using a Boolean that you set to true when your data has loaded.
Your template:
<div v-if='dataLoaded'>Now you can see me.</div>
in your vue instace
export default {
data () {
return {
dataLoaded: false
}
},
created () {
loadMyData().then(data => {
// do awesome things with data
this.dataLoaded = true
})
}
}
This way you can keep your content hidden until that call has resolved. Take care with the context when you handle the ajax response. You will want to keep this as a reference to the original vue instance, so that you can set your data correctly. Arrow functions work well for that.
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.$emit("componentLoaded");
});
}
}
updated: function() {
console.log("updated");
this.$emit("render-vue", this.$el.offsetHeight);
},
This works fine enough...but in my app, props get updated (which I don't care about), and then there is a fetch() that updates data, resulting in additional DOM rendering.
So, that means that I get 2 'updated' events in succession! 👎🏾
Essentially, I only want updated to perform the $emit when data has been fully updated and the DOM is finished.
Currently, $emit is happening 2 times in succession, and that's not helping situation - IT DOM gets updated with props and then right after that another updated occurs when data gets updated after fetch().
Now, I could watch - tried that. The issue there is that $emit will fire off before all DOM is updated, sending the wrong info as argument.
It's almost like I need to watch a specific piece of data...and then, and only then, have updated send the $emit. 😖
For additional context, there are no children - this is a child component.
I can probably get this to work by using a setTimeout()...but come, on! That's sloppy! 👎🏾
In the code block that fetches the data, set a property to indicate new data is available
fetch(url)
.then(() => {
// whatever you're doing with the data
this.newData = true;
});
Check this state variable in the updated hook
updated() {
if (this.newData) {
this.$emit("render-vue", this.$el.offsetHeight);
this.newData = false;
}
}
I have a component with a created method:
created() {
this.initMap();
}
The initMap is to initialize Google maps, depending on whether the URL segment corresponds to 'map' or not like so:
initMap() {
const pathname = location.pathname.replace(/\/+$/, '');
const segment = pathname.split('/').pop();
if (segment === 'map') this.showMap();
}
The above bit of code has a ShowMap method that performs a Vuex commit:
showMap() {
this.$store.commit('showMap');
}
This commit however never shows up in my Vue.js devtools(under Vuex).The components watching the Vuex store value that showMap is changing also never trigger.
If I do this however:
setTimeout(() => {
this.$store.commit('showMap');
, 100);
Everything works exactly as expected.
I tried this because the changes actually happen in my Vue.js devtools, because if I look under state I can see updated values.
The Vuex commit seems to fire too fast. Is there anything that can be done about this? Why is this happening in the first place?
I can even put a console.log() into the showMap commit and it works but it still does not get picked up in the devtools and without the setTimeout all of my watcher still don't properly trigger.
Since this was a while ago I am not 100% sure how I fixed this but I think it was by using $nextTick from Vue.js.
By waiting on nextTick you ensure that your call stack for DOM updates has been cleared. This prevents DOM updates that might rely on other parts of your DOM from firing too fast.
Obviously this is way more reliable than simply setting a setTimeout with a given number of let's say 100 milliseconds from my example because if your DOM does not update in time it might still pass this window.
If setTimeout fixed your issue I suggest trying $nextTick.
https://v2.vuejs.org/v2/api/#Vue-nextTick