I am working on a web app where users can work on a project. The structure of the app is as follows:
Component A (app)
Component B1-Bn (header, footer, main window etc., children of A)
Component C1 (Input area; with inputs for the user to work on the project, child of main window)
Component C2 (Output area; canvas which shows the result based on inputs from C1. In the future also a "graphical" input area that syncs with C1. Child of main window)
Component D1-Dn (Single parts of the input area like tables, advanced input components etc. Child of C1)
Now the project that the user is working on consists of an object stored in Component A. Component Dn needs to write to the object in Component A and also C2 in the future.
I can't get the v-model on input components Dn to work. I tried to pass the data from A down to C1 via props / v-bind and then in Dn, I v-model the prop from C1 (which originates from A) to the input-field. I also tried to use the sync modifier without sucess.
I seem to have a lack of understanding of the vue logic. I come from a desktop background where you just define the scope of variables.
I also found that other vue apprentices have the same understanding problem but somehow the answers I found where not sufficient.
I want a "global" variable that can be edited by every component and is linked to elements in the DOM. What would be the best way to achieve this?
Declare your variable at data when creating Vue Object in your root component (Component A) like
var app = new Vue({
data: function(){
return {
showSetting: {}
}
},
})
Now you can access this showSetting variable in any component like
app.showSetting;
//change it in any component
app.showSetting = {a:1,b:2};
//or append new value to object
Object.assign({d:3},app.showSetting);
Thanks for the answers so far. I guess both of them work. I found another solution because now I fully understand how data is passed in vue:Note that objects and arrays in JavaScript are passed by reference, so if the prop is an array or object, mutating the object or array itself inside the child component will affect parent state. I will pass all data as arrays in the future, as I only want references. The only question that remains is why the programmer is not allowed to define by himself whether the data is passed by reference or not...
Source: Vue.js Guide
Related
I'm making a Form wrapper and I'm wondering how to handle data object prop.
From what I have seen out there, there are some (like FormKit) that mutate the prop object that holds the data. This is not a recommended way according to the official docs. Then there are those (like VueFormulate) that create a shallow copy of the data object before emiting the changed object. To support nested data object you need to deep copy the data object on every change. This seems wasteful with large forms.
Is there an alternative where you don't deep copy an object and you don't mutate object prop?
You could possibly use v-model. as the docs will say, it's shorthand for the child component having a property bound from the parent and when a change event occurs you emit an update event from the child to the parent to have the parent update the property, and the child will subsequently sync to the new value.
ie:
childComponent *has value change*
onChange (value) => this.$emit("updateValue", value)
parentComponent *recieved "updateValue" event*
onUpdateValue(value) => this.parentValue = value
I have Component schema like picture below,
currently when i wan to call table from app.vue i must write
this.$refs.list.$refs.table
is There any way to ignore $refs.list that i can call table directly? like
this.$refs.table
To make a transparent ref It is impossible.
Refs are used to call methods on nested instances. In order not to go deep you should have a method in the list that will call the method in the table.
you need to do composition in a component where a nested ref is needed, this is usually not done. getA (). getB (). doSomething ();
I have got a rather large template at the moment for my component. I want to separate aspects of this into it's own component.
However i'm struggling to pass data to this component. I still want to be able to manipulate the data within the child and have the data in the parent update. So for example if I pass in an object, and then use v-model within the child on a textbox, the changes should reflex within the parent.
So, i'd assume as I loop through the list of objects I would v-model them into my child component, like so:
Main.vue
<card v-for="quote in quotes" v-model="quote"></card>
And then of course accept the input within the new model:
Card.vue
export default {
props: [ 'input' ]
}
However i'm getting the following error and I can't really make sense of it.
You are binding v-model directly to a v-for iteration alias. This will not be able to modify the v-for source array because writing to the alias is like modifying a function local variable. Consider using an array of objects and use v-mode
l on an object property instead.
I am currently generating a table which lists problems encountered during the selected test using a component generated with this code:
<tr is="entry" v-for="problem in problems" :key="problem.id" v-bind:foo="problem"></tr>
Each problem corresponds to an item whose relevant information is contained within the problem dictionary and referenced in the first few columns of the table. Since the same item can have multiple problems, the same item can appear in multiple rows of the table. Now, each row features some buttons which allow you to modify the underlying item so as to fix the problems.
Whenever I modify one of those underlying items I need to modify it in all the rows, which i do by calling a function in the parent component, but modifying the data inside of the dictionary does not seem to trigger any of my watches or computes inside of the child component, which currently looks something like this:
Vue.component('entry', {
props: ['foo'],
data: function(){
//does some computations
return data
},
watch:{
foo: function(){
this.recompute_entry()
},
},
methods:{
//various methods, including:
recompute_entry: function(){
//updates the data according to changes brought to the entry
},
},
});
I have attempted to include a different prop which i could bind to an entry in a list in my parent component but, besides being pretty clunky, that didn't end up working either, which makes me think I might've gotten something wrong with my component.
Ultimately, I have relied on the fact that v-for iterates through my list in an orderly fashion, which combined with the fact that I generate no other children in my parent component means that a child component would have the same index in my component's children array as it would in my problems array. Therefore I can use this:
this.$children[problem_index].recompute_entry();
Which kind of feels hack-ish and unreliable, but actually works, for once. Is there no alternative safer method to recalculate my child components based on changes made to their props? I really feel there has to be.
I probably would need to see the exact implementation but it sounds like you need to clone your dictionary to trigger the prop change, ie:
let newProblem = Object.assign({}, this.problem);
// change any nested property
newProblem.some.value = 1
// assign back the cloned and modified dictionary
this.problem = newProblem
I am working on ExtJS 4.2 now. There are 3 ways to access DOM elements - get, select, query.
I want to know the difference between them. Why three separate methods?
we have a question here: SVO
But it doesn't give me any clear answers. Looking for something specific / detailed answer.
Will be grateful if you can help with the explanation.
Thanks in advance :-)
EDIT based on answer below:
I am not much into jQuery so can't understand through comparison. Can anyone help me with the difference between an Ext.element and a composite element?
EDIT 2:
What is Ext.dom.Element? Any different from Ext.element? and if anyone could throw some light on "Ext.fx.Anim" package?
Ext.get
Ext.get is analogous to document.getElementById in that you can provide the ID of a DOM node and retrieve that element wrapped as Ext.dom.Element. You can also provide a DOM node or an existing Element.
// Main usage: DOM ID
var someEl = Ext.get('myDivId');
// Wrap a DOM node as an Element
var someDom = document.getElementById('myDivId');
someEl = Ext.get(someDom);
// Identity function, essentially
var sameEl = Ext.get(someEl);
Ext.query
Ext.query allows you to select an array of DOM nodes using CSS/XPath selectors. This is handy when working with custom components or data views and you need a more robust selection mechanism than DOM IDs.
// Get all DOM nodes with class "oddRow" that are children of
// my component's top-level element.
var someNodes = Ext.query('.oddRow', myCustomComponent.getEl().dom);
Ext.select
Ext.select is essentially Ext JS's answer to jQuery's selectors. Given some CSS/XPath selector, it returns a single object representing a collection of Elements. This CompositeElement has methods for filtering, iterating, slicing the collection.
Most importantly, the CompositeElement supports chainable versions of all methods of Ext.dom.Element and Ext.fx.Anim that operate on each element in the collection, making this method very powerful.
Edit 1: An Ext.Element represents a single DOM node, while an Ext.dom.CompositeElement represents a collection of DOM nodes that can be affected through a single interface. So, given the following example:
// Set the height of each table row using Ext.query
var tableRowNodes = Ext.query('tr', document.getElementById('myTable'));
Ext.Array.each(tableRowNodes, function (node) {
Ext.fly(node).setHeight(25);
});
// Set the height of each table row using Ext.select
var compositeEl = Ext.select('#myTable tr');
compositeEl.setHeight(25);
You can see how much easier it is to work with Ext.dom.CompositeElement.
Edit 2: Ext JS supports the concept of alternate class names. Think of them as shortcuts for commonly used classes. Ext.Element is the alternate class name for Ext.dom.Element and can be used interchangeably.
Ext.fx.Anim is a class representing an animation. Usually not used directly, it is created behind the scenes when performing animations on elements or components. For example, the first parameter of Ext.Component#hide is the animation target.