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docs: add reduce caveats

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Jeff Sagal
2021-10-22 17:17:18 -07:00
parent 5a6c9bf707
commit 0d294c31bd
2 changed files with 112 additions and 59 deletions
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docs/.vuepress/components/ReducedWithNoMatchingOption.vue
+20
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@@ -0,0 +1,20 @@
<template>
<v-select
v-model="selected"
:reduce="(option) => option.id"
:options="[
{ label: 'One', id: 1 },
{ label: 'Two', id: 2 },
]"
/>
</template>
<script>
export default {
data() {
return {
selected: 3,
}
},
}
</script>
docs/guide/values.md
+92 -59
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@@ -2,11 +2,12 @@
### `v-model`
The most common use case for vue-select is to have the chosen value synced with a parent component. vue-select
takes advantage of the `v-model` syntax to sync values with a parent. The `v-model` syntax works with
primitives and objects.
The most common use case for vue-select is to have the chosen value synced with a parent component.
vue-select takes advantage of the `v-model` syntax to sync values with a parent. The `v-model`
syntax works with primitives and objects.
```html
<v-select v-model="selected" />
```
@@ -14,25 +15,26 @@ Note that when using the `multiple` prop, the `v-model` value will always be an
### Props and Events
Sometimes `v-model` might not fit your use case. For example, when working with [Vuex](https://vuex.vuejs.org),
you'll need to trigger a mutation rather than mutating a value directly. In that case, maybe you need
to bind a pre-selected value, and trigger a mutation when it changes.
Sometimes `v-model` might not fit your use case. For example, when working
with [Vuex](https://vuex.vuejs.org), you'll need to trigger a mutation rather than mutating a value
directly. In that case, maybe you need to bind a pre-selected value, and trigger a mutation when it
changes.
vue-select exposes the `value` prop and an `input` event to enable this. This combo of props and
vue-select exposes the `value` prop and an `input` event to enable this. This combo of props and
events is also how Vue wires up the `v-model` syntax internally.
#### Prop: `value`
The `value` prop lets vue-select know what value is currently selected. It will accept strings,
numbers or objects. If you're using a `multiple` v-select, you'll want to pass an array.
The `value` prop lets vue-select know what value is currently selected. It will accept strings,
numbers or objects. If you're using a `multiple` v-select, you'll want to pass an array.
```html
<v-select :value="selected" />
```
::: tip 🤓
Anytime you bind the `value` prop directly, you're responsible for updating the bound variable
in your code using the `@input` event.
::: tip 🤓 Anytime you bind the `value` prop directly, you're responsible for updating the bound
variable in your code using the `@input` event.
:::
#### Event: `input`
@@ -42,50 +44,66 @@ state as it's only parameter.
#### Vuex Support
The `value` prop and `emit` event are very useful when using a state management tool, like Vuex.
You can bind the selected value with `:value="$store.myValue"`, and use the `input` event to
trigger a mutation, or dispatch an action – or anything else you might need to do when the selection
changes.
The `value` prop and `emit` event are very useful when using a state management tool, like Vuex. You
can bind the selected value with `:value="$store.myValue"`, and use the `input` event to trigger a
mutation, or dispatch an action – or anything else you might need to do when the selection changes.
```html
<v-select :value="$store.myValue" @input="setSelected" />
```
```js
methods: {
setSelected(value) {
// trigger a mutation, or dispatch an action
}
setSelected(value)
{
// trigger a mutation, or dispatch an action
}
}
```
## Single/Multiple
By default, vue-select supports choosing a single value. If you need multiple values, use the
`multiple` boolean prop, much the same way you would on an HTML `<select>` element. When `multiple`
is true, `v-model` and `value` must be an array.
```html
<v-select multiple v-model="selected" :options="['Canada','United States']" />
```
<v-select multiple :options="['Canada','United States']" />
## Transforming Selections
When the `options` array contains objects, vue-select returns the whole object as dropdown value
When the `options` array contains objects, vue-select returns the whole object as dropdown value
upon selection. This approach makes no assumptions about the data you need, and provides a lot of
flexibility. However, there will be situations where maybe you just need to return a single key
from an object.
flexibility. However, there will be situations where you just need to return a single key from an
object.
### Returning a single key with `reduce`
### Returning a single key with `reduce`
If you need to return a single key, or transform the selection before it is synced, vue-select
provides a `reduce` callback that allows you to transform a selected option before it is passed to
If you need to return a single key, or transform the selection before it is synced, vue-select
provides a `reduce` callback that allows you to transform a selected option before it is passed to
the `@input` event. Consider this data structure:
```js
let options = [{code: 'CA', country: 'Canada'}];
```
If we want to display the `country`, but return the `code` to `v-model`, we can use the `reduce`
If we want to display the `country`, but return the `code` to `v-model`, we can use the `reduce`
prop to receive only the data that's required.
```html
<v-select :options="options" :reduce="country => country.code" label="country" />
<v-select :options="options" :reduce="country => country.code" label="country" />
```
### Deep Nested Values
The `reduce` property also works well when you have a deeply nested value:
```
{
country: 'canada',
@@ -95,30 +113,42 @@ The `reduce` property also works well when you have a deeply nested value:
}
}
```
```html
<v-select :options="options" :reduce="country => country.meta.code" label="country" />
<v-select :options="options" :reduce="country => country.meta.code" label="country" />
```
<reducer-nested-value />
## Single/Multiple Selection
## Caveats with `reduce`
By default, vue-select supports choosing a single value. If you need multiple values, use the
`multiple` boolean prop, much the same way you would on an HTML `<select>` element. When `multiple`
is true, `v-model` and `value` must be an array.
The most common issue with `reduce` is when the component displays your _reduced_ _value_ instead of
it's _label_. This happens when you supply Vue Select a `value` or `v-model` binding with a reduced_
value, but the complete option object is not present in the `options` array.
```html
<v-select multiple v-model="selected" :options="['Canada','United States']" />
```
<v-select multiple :options="['Canada','United States']" />
<ReducedWithNoMatchingOption />
<<< @/.vuepress/components/ReducedWithNoMatchingOption.vue
In the example above, the component was supplied with an ID that doesn't exist in the `options`
array. When `value` changes, Vue Select searches the supplied options, running each one
through `reduce` until the corresponding option is found. When that option doesn't exist, Vue Select
will end up displaying the `value` supplied.
::: warning
When providing Vue Select with a _reduced_ `value` - the object that the value was reduced from must
exist in the `options` array.
:::
## Tagging
To allow input that's not present within the options, set the `taggable` prop to true.
```html
<v-select taggable multiple />
```
@@ -127,6 +157,7 @@ To allow input that's not present within the options, set the `taggable` prop to
If you want added tags to be pushed to the options array, set `push-tags` to true.
```html
<v-select taggable multiple push-tags />
```
@@ -136,10 +167,11 @@ If you want added tags to be pushed to the options array, set `push-tags` to tru
When combining `taggable` with `reduce`, you must define the `createOption` prop. The
`createOption` function is responsible for defining the structure of the objects that Vue Select
will create for you when adding a tag. It should return a value that has the same properties as the
will create for you when adding a tag. It should return a value that has the same properties as the
rest of your `options`.
If you don't define `createOption`, Vue Select will construct a simple object following this structure:
If you don't define `createOption`, Vue Select will construct a simple object following this
structure:
`{[this.label]: searchText}`. If you're using `reduce`, this is probably not what your options look
like, which is why you'll need to set the function yourself.
@@ -147,28 +179,29 @@ like, which is why you'll need to set the function yourself.
We have a taggable select for adding books to a collection. We're just concerned about getting the
book title added, and our server side code will add the author details in a background process. The
user has already selected a book.
user has already selected a book.
```js
const options = [
{
title: "HTML5",
author: {
firstName: "Remy",
lastName: "Sharp"
{
title: "HTML5",
author: {
firstName: "Remy",
lastName: "Sharp"
}
}
}
];
```
```html
<v-select
taggable
multiple
label="title"
:options="options"
:create-option="book => ({ title: book, author: { firstName: '', lastName: '' } })"
:reduce="book => `${book.author.firstName} ${book.author.lastName}`"
taggable
multiple
label="title"
:options="options"
:create-option="book => ({ title: book, author: { firstName: '', lastName: '' } })"
:reduce="book => `${book.author.firstName} ${book.author.lastName}`"
/>
```