mount on a component does not fire for v-bind changes to the component in the root.
I have a dynamic component where I often change the value of the data referenced in v-bind:is and v-bind attributes, switching the current component and its data. This works great to show different "screens" of my application.
I have some logic that happens on mount for many of the components. However, this only gets called when the v-bind:is value is changed, but no when only the v-bind attribute is. That sort of makes sense to me, though I do need to capture either.
I'm new to Vue and there is a lot of documentation. I'm so far unable to determine if there's a built-in functionality for a callback to v-bind:is and v-bind. Can anyone help me out here?
Related
I'm new to vue, and what i would really want to do is to have the possibility to insert a component into another component, without knowing the name of the component.
What i can do, at the moment, is to create a component "componentA" in which i make use of another component "componentB".
However, my goal would be to have componentA declare that it wants to use some component, when it doesn't yet know the component's name. Then, obtain the component's reference through props (or wherever) and use it.
In the same way that, through props, a component can obtain information without knowing what it's gonna be, i would like to know if the component can receive another component and make use of it, without knowing what the component is gonna be.
Is there a way to achieve this in vue.js?
Edit: It can be done by using Dynamic Components. Thank for providing the answer in the comments.
I am creating a Vue component ("Polar") to layout divs in a circular pattern. It does so setting the inline styles.
Now, I am having a weird issue when I use the component. It happens only under a very specific set of circumstances:
I create multiple instances through v-for
The Polar component is a "functional" component
I pass the props as a referenced object (inline works fine!)
The propsObject contains a nested StylesObject
The custom Styles object gets merged as the first parameter of ObjectAssign()
What happens? All the instances in the v-for take on the value of the last item, like a closure was broken.
The code is a bit much to display here, so I have a codesandbox and github. The first test shows the issue: all items are displayed on top of each other. The second test demonstrates that I can pass the exact same propsObject, only inline, and it works. Reversing the arguments in Object.assign also makes it work, as does converting the component to a normal/non-functional one.
I suspect this is some sort of Vue bug (or at least undocumented behavior).
Quick answer:
Object.assign will change the first parameter (=target object). This caused my settingsObj to take on the other settings every time, until it had the settings of the last instance.
Easily resolved by changing
Object.assign(props.settingsObj, {setting: val, })
into
Object.assign({}, props.settingsObj, {setting: val, })
Sorry for blaming Vue, all my fault. Not exactly sure why this only happens with functional components, but it must be related to normal components being isolated in their own Vue instance.
I construct deep nested tree of parent and children Vue custom components using my top level component dynamically and then I am updating the data from which all tree is constructed. Which has an effect of rendering the entire tree (its a form with various custom components). I refresh/rebuild the whole form after fetching the data (which is what vue do for reactive data) that itself tell me how to regenerate the view (its like a JSON Schema from which I render the entire view).
This is related to my other issue here.
I am observing a very weird behavior in my Vue Application. When I destroy all my children components and rebuild the data to force rendering the form, it appears that even after I have called $destroy on every child component...Vue is not entirely removing them from cache?
Does vue remove the component from cache if a $destroy is called ?
Because I do not see multiple components of the same type in the Vue component list in the Chrome Vue DevTool extension panel. But I see that the same custom event is handled twice by the same component. Same function that handle the events is getting called twice even though there is only one component visible in Vue DevTools of this type.
This only happens after I render the form. When the page is loaded for the first time every thing works. Then after I reset the form by destroying the child component and resetting the data to re-render the form, magically this child component start handling the event twice.. and in 3rd render it handle the events thrice. But I see only one component in google chrome VueJS DevTool extension panel. So my guess is that vue is still keeping the previously destroyed component in cache. I am trying to figure out how should I destroy those components in the cache.
If anyone has observed something similar and found a solution please let me know.
At the moment I am going to dig little bit more on my component keys (this particular component does not have explicit key set by me).
First and foremost, the vue documentation states:
vm.$destroy
In normal use cases you shouldn’t have to call this method yourself.
Prefer controlling the lifecycle of child components in a data-driven
fashion using v-if and v-for.
So instead of destroying and rebuilding the components manually yourself, you should really letting vue handle that via v-if and v-for. If the components aren't updating to your changes, you might be dealing with a reactivity issue.
As you mentioned that this is a deeply nested structure, the reactivity is key to keeping the components up to data with the data.
Vue does not allow dynamically adding new root-level reactive properties to an already created instance. However, it’s possible to add reactive properties to a nested object using the Vue.set(object, key, value) method:
Vue.set(vm.someObject, 'b', 2)
Inside of a component:
this.$set(this.someObject, 'b', 2)
Also, keep in mind that Vue should be doing the heavy lifting in regards to component management, while you should define the parameters by which a component is rendered.
I know in vue, I can use this.$parent to get the upper component in the vdom tree. But I'm expecting something different: to get the component that rendered the current component.
For instance, I have a component (named comp-container) with template:
<template>
<comp-a>
<comp-b></comp-b>
</comp-a>
</template>
And in comp-b the $parent would be an instance of comp-a not comp-container which I'm expecting.
My current aproach is traversing up with the $parent attribute until I find comp-b exists in $options.components. This method is working for now but seems quite ugly and breaks if comp-b is a globaly registered component. Is there an official way to do this?
Passing the parent template component via props as <comp-b :container="this"></comp-b> may do the job, but it's too verbose to be liked.
I'm not sure about the exact use case, but basically if there are slots involved (which I almost assume, because otherwise $parent will work fine), you can find the rendering component at:
this.$slots.default[0].context;
Basically, the context property of a slot is the rendering context (rendering component - i.e. the component who's template the component was rendered in).
Only tested with Vue 2
I am trying to create fully reusable component using Vue.js 2 and single file components, and right now my approach seems to be impossible to realize.
The goal is to create component for creating forms for a complex, nested JSON structure. This structure is supposed to be edited and then sent to the server. The component itself displays a header and submit button but the fields along with their placing is entirely the responsibility of the user of my component. (front-end engineer)
The MyForm component (implementation is not relevant here) is passed the JSON data and url to post them to.
The form is supposed to be reusable by many other users and the contents of the form itself is supposed to be not relevant. It may have a mix of html/inputs/custom components as children.
Let's imagine a simple scenario without data nesting with the following data:
var mymodel={ name : "My name", surname : "My surname" }
And a form i would like to create using my component:
<MyForm :model="mymodel" :url="http://localhost/post">
<div>
<MyTextInput v-model="model.name" label="Name"/>
<MyPanel>
<MyTextInput v-model="model.surname" label="Surname"/>
</MyPanel>
</div>
</MyForm>
Therefore:
MyForm gets passed a model to submit, stores it in data
MyTextInput is a custom component for displaying input with label
Second MyTextInput is the same component but created in another component contained called 'MyPanel' since this field needs to be placed differently.
As we can see there are many problems with passing variables and composition itself:
Composition:
If i put a <slot></slot> in the tempplate of MyForm for displaying the fields it would be compiled in parent scope, therefore all children (including MyTextField) would not have access to the "model"
If i try to use <MyForm inline-template> i cannot automatically display the form header and footer since all content is being replaced. Additionally when using single file components the compiler will look for all components inside the inline-template which means that i would have to import MyTextInput and MyPanel into MyForm which is not practical. I do not know in advance all components that will never end up in my form!
Passing variables:
If i use the variables directly from "model" (in first TextInput) i receive warning that i am modifying a variable from parent and it will be overwritten on next render (but in this case it will not be overwritten since i am INTENTIONALLY modifying the parent)
I cannot pass the model into second MyTextInput without passing it to MyPanel first. Actually i would have to pass it into EVERY custom component in between. And i do not know in advance how many custom components will there be. Which means that i would have to modify the code of every component that would ever be put into MyForm and require users to pass the data for each custom component they include.
If i would try to properly inform the parent about changes i would need to add v-on: event to every textinput and every custom component in between in order for the event to reach MyForm.
As i have said the component was supposed to be simple and easilly reusable. Requiring users of this component to modify code of every child they put into it and requiring them to add v-on: to every component inside does not seem practical.
Is my idea solvable using Vue.js 2.0 ? I have designed the same component before for AngularJS (1.5) and it was working fine and did not require to add modifications to each child of the form.
I've been using a ui framework based on vue 2.0 and you may get some ideas from its implementation. Based on its implementaion and my little experience with it, I think it's the person who uses your framework's responsibility to assemble the form-model. Also, for a form, we can always easily get all the data to be sent by using fields' value props without v-model's help.
The framework's doc on form element may also be helpful but it's currently only available in Chinese except for the code samples.
I suggest you to use Form Input Components using Custom Events to pass variables in your form.
Mutating a prop locally is now considered an anti-pattern, e.g.
declaring a prop a and then set this.a = someOtherValue in the
component. Due to the new rendering mechanism, whenever the parent
component re-renders, the child component's local changes will be
overwritten. In general, in 2.0 you should treat props as immutable.
Most use cases of mutating a prop can be replaced by either a data
property or a computed property.