How to generate computed props on the fly while accessing the Vue instance? - vue.js

Question

I was wondering if there is a way of creating computed props programatically, while still accessing the instance to achieve dynamic values
Something like that (this being undefined below)
<script>
export default {
computed: {
...createDynamicPropsWithTheContext(this), // helper function that returns an object
}
}
</script>
On this question, there is a solution given by Linus: https://forum.vuejs.org/t/generating-computed-properties-on-the-fly/14833/4 looking like
computed: {
...mapPropsModels(['cool', 'but', 'static'])
}
This works fine but the main issue is that it's fully static. Is there a way to access the Vue instance to reach upon props for example?
More context
For testing purposes, my helper function is as simple as
export const createDynamicPropsWithTheContext = (listToConvert) => {
return listToConvert?.reduce((acc, curr) => {
acc[curr] = curr
return acc
}, {})
}
What I actually wish to pass down to this helper function (via this) are props that are matching a specific prefix aka starting with any of those is|can|has|show (I'm using a regex), that I do have access via this.$options.props in a classic parent/child state transfer.
The final idea of my question is mainly to avoid manually writing all the props manually like ...createDynamicPropsWithTheContext(['canSubmit', 'showModal', 'isClosed']) but have them populated programatically (this pattern will be required in a lot of components).
The props are passed like this
<my-component can-submit="false" show-modal="true" />
PS: it's can-submit and not :can-submit on purpose (while still being hacked into a falsy result right now!).
It's for the ease of use for the end user that will not need to remember to prefix with :, yeah I know...a lot of difficulty just for a semi-colon that could follow Vue's conventions.

Answer 1

You could use the setup() hook, which receives props as its first argument. Pass the props argument to createDynamicPropsWithTheContext, and spread the result in setup()'s return (like you had done previously in the computed option):
import { createDynamicPropsWithTheContext } from './props-utils'
export default {
⋮
setup(props) {
return {
...createDynamicPropsWithTheContext(props),
}
}
}
demo

Answer 2

If the whole thing is for avoiding using a :, then you might want to consider using a simple object (or array of objects) as data source. You could just iterate over a list and bind the data to the components generated. In this scenario the only : used are in the objects
const comps = [{
"can-submit": false,
"show-modal": true,
"something-else": false,
},
{
"can-submit": true,
"show-modal": true,
"something-else": false,
},
{
"can-submit": false,
"show-modal": true,
"something-else": true,
},
]
const CustomComponent = {
setup(props, { attrs }) {
return {
attrs
}
},
template: `
<div
v-bind="attrs"
>{{ attrs }}</div>
`
}
const vm = Vue.createApp({
setup() {
return {
comps
}
},
template: `
<custom-component
v-for="(item, i) in comps"
v-bind="item"
></custom-component>
`
})
vm.component('CustomComponent', CustomComponent)
vm.mount('#app')
<script src="https://unpkg.com/vue#3"></script>
<div id="app">{{ message }}</div>

Answer 3

Thanks to Vue's Discord Cathrine and skirtle folks, I achieved to get it working!
Here is the thread and here is the SFC example that helped me, especially this code
created () {
const magicIsShown = computed(() => this.isShown === true || this.isShown === 'true')
Object.defineProperty(this, 'magicIsShown', {
get () {
return magicIsShown.value
}
})
}
Using Object.defineProperty(this... is helping keeping the whole state reactive and the computed(() => can reference some other prop (which I am looking at in my case).
Using a JS object could be doable but I have to have it done from the template (it's a lower barrier to entry).
Still, here is the solution I came up with as a global mixin imported in every component.
// helper functions
const proceedIfStringlean = (propName) => /^(is|can|has|show)+.*/.test(propName)
const stringleanCase = (string) => 'stringlean' + string[0].toUpperCase() + string.slice(1)
const computeStringlean = (value) => {
if (typeof value == 'string') {
return value == 'true'
}
return value
}
// the actual mixin
const generateStringleans = {
created() {
for (const [key, _value] of Object.entries(this.$props)) {
if (proceedIfStringlean(key)) {
const stringleanComputed = computed(() => this[key])
Object.defineProperty(this, stringleanCase(key), {
get() {
return computeStringlean(stringleanComputed.value)
},
// do not write any `set()` here because this is just an overlay
})
}
}
},
}
This will scan every .vue component, get the passed props and if those are prefixed with either is|can|has|show, will create a duplicated counter-part with a prefix of stringlean + pass the initial prop into a method (computeStringlean in my case).
Works great, there is no devtools support as expected since we're wiring it directly in vanilla JS.