浅谈Vue3 defineComponent有什么作用

defineComponent函数,只是对setup函数进行封装,返回options的对象;

export function defineComponent(options: unknown) {

return isFunction(options) ? { setup: options } : options

}

defineComponent最重要的是:在TypeScript下,给予了组件 正确的参数类型推断 。

在这里插入图片描述

defineComponent重载函数

1:direct setup function

// overload 1: direct setup function

// (uses user defined props interface)

export function defineComponent<Props, RawBindings = object>(

setup: (

props: Readonly<Props>,

ctx: SetupContext

) => RawBindings | RenderFunction

): DefineComponent<Props, RawBindings>

在这里插入图片描述

2:object format with no props

// overload 2: object format with no props

// (uses user defined props interface)

// return type is for Vetur and TSX support

export function defineComponent<

Props = {},

RawBindings = {},

D = {},

C extends ComputedOptions = {},

M extends MethodOptions = {},

Mixin extends ComponentOptionsMixin = ComponentOptionsMixin,

Extends extends ComponentOptionsMixin = ComponentOptionsMixin,

E extends EmitsOptions = EmitsOptions,

EE extends string = string

>(

options: ComponentOptionsWithoutProps<Props,RawBindings,D,C,M,Mixin,Extends,E,EE>

): DefineComponent<Props, RawBindings, D, C, M, Mixin, Extends, E, EE>

在这里插入图片描述

3:object format with array props declaration

// overload 3: object format with array props declaration

// props inferred as { [key in PropNames]?: any }

// return type is for Vetur and TSX support

export function defineComponent<

PropNames extends string,

RawBindings,

D,

C extends ComputedOptions = {},

M extends MethodOptions = {},

Mixin extends ComponentOptionsMixin = ComponentOptionsMixin,

Extends extends ComponentOptionsMixin = ComponentOptionsMixin,

E extends EmitsOptions = Record<string, any>,

EE extends string = string

>(

options: ComponentOptionsWithArrayProps<

PropNames,

RawBindings,...>

): DefineComponent<

Readonly<{ [key in PropNames]?: any }>,

RawBindings,...>

在这里插入图片描述

4: object format with object props declaration

// overload 4: object format with object props declaration

// see `ExtractPropTypes` in ./componentProps.ts

export function defineComponent<

// the Readonly constraint allows TS to treat the type of { required: true }

// as constant instead of boolean.

PropsOptions extends Readonly<ComponentPropsOptions>,

RawBindings,

D,

C extends ComputedOptions = {},

M extends MethodOptions = {},

Mixin extends ComponentOptionsMixin = ComponentOptionsMixin,

Extends extends ComponentOptionsMixin = ComponentOptionsMixin,

E extends EmitsOptions = Record<string, any>,

EE extends string = string

>(

options: ComponentOptionsWithObjectProps<

PropsOptions, RawBindings, D, C, M, Mixin, Extends, E, EE>

): DefineComponent<PropsOptions, RawBindings, D, C, M, Mixin, Extends, E, EE>

在这里插入图片描述

开发实践

除去单元测试中几种基本的用法,在以下的 ParentDialog 组件中,主要有这几个实际开发中要注意的点:

自定义组件和全局组件的写法

inject、ref 等的类型约束

setup 的写法和相应 h 的注入问题

tsx 中 v-model 和 scopedSlots 的写法

ParentDialog.vue

<script lang="tsx">

import { noop, trim } from 'lodash';

import {

inject, Ref, defineComponent, getCurrentInstance, ref

} from '@vue/composition-api';

import filters from '@/filters';

import CommonDialog from '@/components/CommonDialog';

import ChildTable, { getEmptyModelRow } from './ChildTable.vue';

export interface IParentDialog {

show: boolean;

specFn: (component_id: HostComponent['id']) => Promise<{ data: DictSpecs }>;

}

export default defineComponent<IParentDialog>({

// tsx 中自定义组件依然要注册

components: {

ChildTable

},

props: {

show: {

type: Boolean,

default: false

},

specFn: {

type: Function,

default: noop

}

},

// note: setup 须用箭头函数

setup: (props, context) => {

// 修正 tsx 中无法自动注入 'h' 函数的问题

// eslint-disable-next-line no-unused-vars

const h = getCurrentInstance()!.$createElement;

const { emit } = context;

const { specFn, show } = props;

// filter 的用法

const { withColon } = filters;

// inject 的用法

const pageType = inject<CompSpecType>('pageType', 'foo');

const dictComponents = inject<Ref<DictComp[]>>('dictComponents', ref([]));

// ref的类型约束

const dictSpecs = ref<DictSpecs>([]);

const loading = ref(false);

const _lookupSpecs = async (component_id: HostComponent['id']) => {

loading.value = true;

try {

const json = await specFn(component_id);

dictSpecs.value = json.data;

} finally {

loading.value = false;

}

};

const formdata = ref<Spec>({

component_id: '',

specs_id: '',

model: [getEmptyModelRow()]

});

const err1 = ref('');

const err2 = ref('');

const _doCheck = () => {

err1.value = '';

err2.value = '';

const { component_id, specs_id, model } = formdata.value;

if (!component_id) {

err1.value = '请选择部件';

return false;

}

for (let i = 0; i < model.length; i++) {

const { brand_id, data } = model[i];

if (!brand_id) {

err2.value = '请选择品牌';

return false;

}

if (

formdata.value.model.some(

(m, midx) => midx !== i && String(m.brand_id) === String(brand_id)

)

) {

err2.value = '品牌重复';

return false;

}

}

return true;

};

const onClose = () => {

emit('update:show', false);

};

const onSubmit = async () => {

const bool = _doCheck();

if (!bool) return;

const params = formdata.value;

emit('submit', params);

onClose();

};

// note: 在 tsx 中,element-ui 等全局注册的组件依然要用 kebab-case 形式 ????‍

return () => (

<CommonDialog

class="comp"

title="新建"

width="1000px"

labelCancel="取消"

labelSubmit="确定"

vLoading={loading.value}

show={show}

onClose={onClose}

onSubmit={onSubmit}

>

<el-form labelWidth="140px" class="create-page">

<el-form-item label={withColon('部件类型')} required={true} error={err1.value}>

<el-select

class="full-width"

model={{

value: formdata.value.component_id,

callback: (v: string) => {

formdata.value.component_id = v;

_lookupSpecs(v);

}

}}

>

{dictComponents.value.map((dictComp: DictComp) => (

<el-option key={dictComp.id} label={dictComp.component_name} value={dictComp.id} />

))}

</el-select>

</el-form-item>

{formdata.value.component_id ? (

<el-form-item labelWidth="0" label="" required={true} error={err2.value}>

<child-table

list={formdata.value.model}

onChange={(v: Spec['model']) => {

formdata.value.model = v;

}}

onError={(err: string) => {

err3.value = err;

}}

scopedSlots={{

default: (scope: any) => (

<p>{ scope.foo }</p>

)

}}

/>

</el-form-item>

) : null}

</el-form>

</CommonDialog>

);

}

});

</script>

<style lang="scss" scoped>

</style>

全文总结

  • 引入 defineComponent() 以正确推断 setup() 组件的参数类型
  • defineComponent 可以正确适配无 props、数组 props 等形式
  • defineComponent 可以接受显式的自定义 props 接口或从属性验证对象中自动推断
  • 在 tsx 中,element-ui 等全局注册的组件依然要用 kebab-case 形式
  • 在 tsx 中,v-model 要用 model={{ value, callback }} 写法
  • 在 tsx 中,scoped slots 要用 scopedSlots={{ foo: (scope) => () }} 写法
  • defineComponent 并不适用于函数式组件,应使用 RenderContext 解决

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