I had an API call to the backend and based on the returned data, I set the reactive data dynamically:
let data = {
quantity: [],
tickets: []
}
api.default.fetch()
.then(function (tickets) {
data.tickets = tickets
tickets.forEach(ticket => {
data.quantity[ticket.id] = 0
})
})
Based on this flow, how can I set watcher for all reactive elements in quantity array dynamically as well?
You can create a computed property, where you can stringify the quantity array, and then set a watcher on this computed property. Code will look something like following:
computed: {
quantityString: function () {
return JSON.stringify(this.quantity)
}
}
watch: {
// whenever question changes, this function will run
quantityString: function (newQuantity) {
var newQuantity = JSON.parse(newQuantity)
//Your relevant code
}
}
Using the [] operator to change a value in an array won't let vue detect the change, use splice instead.
Related
Having problem to use state in data function of Vue.
I tried this
this.items = this.$store.state.search_items
but it always results in an empty array like this
[__ob__: Observer]
length: 0
__ob__: Observer {value: Array(0), dep: Dep, vmCount: 0}
__proto__: Array
Any help would be appreciated. Thank you !!
Here is the mutation from which I am stating search_items
this is working because I am able to see state.search_items in Vue dev tool
SET_WORKSPACES(state, payload) {
state.workspaces = payload;
var items = [];
if (state.workspaces.length) {
state.workspaces.forEach(function(workspace) {
// Adding workspaces
if (workspace.portfolios.length) {
items = [...items, ...workspace.portfolios];
}
// Adding projects
if (workspace.projects.length) {
items = [...items, ...workspace.projects];
// Adding tasks
workspace.projects.forEach(function(project) {
if (project.tasks.length) {
items = [...items, ...project.tasks];
}
});
}
});
}
state.search_items = items;
}
Data property
data() {
return {
results: [],
keys: ['title','description'],
list:this.items,
}
},
If the state is updating correctly, the time taking for setting the state is making the issue. That means, the the function you're using to assign the state to data is rendering before the state set.
You can use a computed function that returning the state
computed:{
items : function(){
return this.$store.state.search_items;
}
}
Now you can use the computed function name items same like a data variable.
I am trying to send an array containing arrays which in turn contains objects to one component from another, but the content from the array seems to be empty in the child component.
I have tried sending the data as a String using JSON.Stringify() and also as an array
My parent component:
data: function(){
return{
myLineItems : []
}
},
created(){
this.CreateLineItems();
},
methods:{
CreateLineItems(){
let myArrayData = [[{"title":"Title1","value":2768.88}],[{"title":"Title2","value":9}],[{"title":"Title3","value":53.61},{"title":"Title4","value":888.77},{"title":"Title5","value":1206.11},{"title":"Title6","value":162.5}]]
this.myLineItems = myArrayData;
}
}
My parent component's template:
/*
template: `<div><InvoiceChart v-bind:lineItems="myLineItems"></InvoiceChart></div>`
My child component:
const ChildComponent= {
props: {
lineItems: {
type: Array
}
},
mounted() {
console.log(this.lineItems);
}
};
The parent component is created as so (inside a method of our main component):
var ComponentClass = Vue.extend(InvoiceDetails);
var instance = new ComponentClass({
propsData: { invoiceid: invoiceId }
});
instance.$mount();
var elem = this.$refs['details-' + invoiceId];
elem[0].innerHTML = "";
elem[0].appendChild(instance.$el);
If I try to do a console.log(this) inside the childcomponent, I can see the correct array data exist on the lineItems property..but i can't seem to access it.
I have just started using VueJS so I haven't quite gotten a hang of the dataflow here yet, though I've tried reading the documentation as well as similar cases here on stackoverflow to no avail.
Expected result: using this.lineItems should be a populated array of my values sent from the parent.
Actual results: this.lineItems is an empty Array
Edit: The problem seemed to be related to how I created my parent component:
var ComponentClass = Vue.extend(InvoiceDetails);
var instance = new ComponentClass({
propsData: { invoiceid: invoiceId }
});
instance.$mount();
var elem = this.$refs['details-' + invoiceId];
elem[0].innerHTML = "";
elem[0].appendChild(instance.$el);
Changing this to a regular custom vue component fixed the issue
Code - https://codesandbox.io/s/znl2yy478p
You can print your object through function JSON.stringify() - in this case all functions will be omitted and only values will be printed.
Everything looks good in your code.
The issue is the property is not correctly getting passed down, and the default property is being used.
Update the way you instantiate the top level component.
Try as below =>
const ChildComponent= {
props: {
lineItems: {
type: Array
}
},
mounted() {
console.log(this.lineItems);
}
};
I am trying to update a single property of an object from an array using vuex.
here is my code in store file.
export default{
namespaced: true,
state: {
customers: null,
},
mutations: {
UPDATE_MODIFIED_STATE(state, value) {
state.customers = [
...state.customers.filter(item => item.Id !== value.Id),
value,
];
},
},
And below code is from my .vue file.
export default {
computed: {
customerArray() {
return this.$store.state.CustomerStore.customers;
},
},
methods: {
...mapMutations('CustomerStore', ['UPDATE_MODIFIED_STATE']),
updateCustomers() {
if(someCondition) {
this.customerArray.forEach((element) => {
element.IsModified = true;
this.UPDATE_MODIFIED_STATE(element);
});
}
/// Some other code here
},
},
};
As you can see I want to update IsModified property of object.
It is working perfectly fine. it is updating the each customer object.
Just want to make sure, is it correct way to update array object or I should use Vue.set.
If yes, I should use Vue.set, then How can I use it here.
You are actually not mutating your array, what you do is replacing the original array with a new array generated by the filter function and the passed value. So in your example there is no need to use Vue.set.
You can find more information about replacing an array in the vue documentation.
The caveats begin however when you directly set an item with the index or when you modify the length of the array. When doing this the data will no longer be reactive, you can read more about this here.
For example, consider the following inside a mutation:
// If you update an array item like this it will no longer be reactive.
state.customers[0] = { Id: 0, IsModified: true }
// If you update an array item like this it will remain reactive.
Vue.set(state.customers, 0, { Id: 0, IsModified: true })
I'm learning Vue and have been struggling to get the data from a computed property. I am retrieving comments from the store and them processing through a function called chunkify() however I'm getting the following error.
Despite the comments being computed correctly.
What am I doing wrong here? Any help would be greatly appreciated.
Home.vue
export default {
name: 'Home',
computed: {
comments() {
return this.$store.state.comments
},
},
methods: {
init() {
const comments = this.chunkify(this.comments, 3);
comments[0] = this.chunkify(comments[0], 3);
comments[1] = this.chunkify(comments[1], 3);
comments[2] = this.chunkify(comments[2], 3);
console.log(comments)
},
chunkify(a, n) {
if (n < 2)
return [a];
const len = a.length;
const out = [];
let i = 0;
let size;
if (len % n === 0) {
size = Math.floor(len / n);
while (i < len) {
out.push(a.slice(i, i += size));
}
} else {
while (i < len) {
size = Math.ceil((len - i) / n--);
out.push(a.slice(i, i += size));
}
}
return out;
},
},
mounted() {
this.init()
}
}
Like I wrote in the comments, the OPs problem is that he's accessing a store property that is not available (probably waiting on an AJAX request to come in) when the component is mounted.
Instead of eagerly assuming the data is present when the component is mounted, I suggested that the store property be watched and this.init() called when the propery is loaded.
However, I think this may not be the right approach, since the watch method will be called every time the property changes, which is not semantic for the case of doing prep work on data. I can suggest two solutions that I think are more elegant.
1. Trigger an event when the data is loaded
It's easy to set up a global messaging bus in Vue (see, for example, this post).
Assuming that the property is being loaded in a Vuex action,the flow would be similar to:
{
...
actions: {
async comments() {
try {
await loadComments()
EventBus.trigger("comments:load:success")
} catch (e) {
EventBus.trigger("comments:load:error", e)
}
}
}
...
}
You can gripe a bit about reactivity and events going agains the reactive philosophy. But this may be an example of a case where events are just more semantic.
2. The reactive approach
I try to keep computation outside of my views. Instead of defining chunkify inside your component, you can instead tie that in to your store.
So, say that I have a JavaScrip module called store that exports the Vuex store. I would define chunkify as a named function in that module
function chunkify (a, n) {
...
}
(This can be defined at the bottom of the JS module, for readability, thanks to function hoisting.)
Then, in your store definition,
const store = new Vuex.Store({
state: { ... },
...
getters: {
chunkedComments (state) {
return function (chunks) {
if (state.comments)
return chunkify(state.comments, chunks);
return state.comments
}
}
}
...
})
In your component, the computed prop would now be
computed: {
comments() {
return this.$store.getters.chunkedComments(3);
},
}
Then the update cascase will flow from the getter, which will update when comments are retrieved, which will update the component's computed prop, which will update the ui.
Use getters, merge chuckify and init function inside the getter.And for computed comment function will return this.$store.getters.YOURFUNC (merge of chuckify and init function). do not add anything inside mounted.
I need to check variable rasters_previews_list for changing. Here is my code:
var userContent = Vue.extend({
template: '<p>Some template</p>',
data: function () {
return {
rasters_previews_list: []
}
},
watch: {
'rasters_previews_list': function(value, mutation) {
console.log("Value changed");
}
}
});
But In console I do not see Value changed when it got new data.
Data changing function:
map.on('draw:created', function (e) {
//...
Vue.http.post('/dbdata', DataBody).then((response) => {
userContent.rasters_previews_list = response; // putting JSON answer to Component data in userContent
console.log(response);
}, (response) => {
console.log("Can't get list rasters metadata from DB. Server error: ", response.status)
});
I change value in map.on('draw:created', function (e) (Leaflet JS). I see console.log output, so seems data is changing.
If you want to change the value of an array you will have to use the special Array extension methods Vue.set and Vue.delete.
Due to limitations of JavaScript, Vue cannot detect the following changes to an Array:
When you directly set an item with the index, e.g. vm.items[0] = {};
When you modify the length of the Array, e.g. vm.items.length = 0.
https://vuejs.org/api/#Vue-set
This problem is also mentioned in the common gotchas
When you modify an Array by directly setting an index (e.g. arr[0] = val) or modifying its length property. Similarly, Vue.js cannot pickup these changes. Always modify arrays by using an Array instance method, or replacing it entirely. Vue provides a convenience method arr.$set(index, value) which is just syntax sugar for arr.splice(index, 1, value).