extend.ts
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import { ASSET_TYPES } from 'shared/constants'
import type { Component } from 'types/component'
import type { GlobalAPI } from 'types/global-api'
import { defineComputed, proxy } from '../instance/state'
import { extend, mergeOptions, validateComponentName } from '../util/index'
import { getComponentName } from '../vdom/create-component'
export function initExtend(Vue: GlobalAPI) {
/**
* Each instance constructor, including Vue, has a unique
* cid. This enables us to create wrapped "child
* constructors" for prototypal inheritance and cache them.
*/
Vue.cid = 0
let cid = 1
/**
* Class inheritance
*/
Vue.extend = function (extendOptions: any): typeof Component {
extendOptions = extendOptions || {}
const Super = this
const SuperId = Super.cid
const cachedCtors = extendOptions._Ctor || (extendOptions._Ctor = {})
if (cachedCtors[SuperId]) {
return cachedCtors[SuperId]
}
const name =
getComponentName(extendOptions) || getComponentName(Super.options)
if (__DEV__ && name) {
validateComponentName(name)
}
const Sub = function VueComponent(this: any, options: any) {
this._init(options)
} as unknown as typeof Component
Sub.prototype = Object.create(Super.prototype)
Sub.prototype.constructor = Sub
Sub.cid = cid++
Sub.options = mergeOptions(Super.options, extendOptions)
Sub['super'] = Super
// For props and computed properties, we define the proxy getters on
// the Vue instances at extension time, on the extended prototype. This
// avoids Object.defineProperty calls for each instance created.
if (Sub.options.props) {
initProps(Sub)
}
if (Sub.options.computed) {
initComputed(Sub)
}
// allow further extension/mixin/plugin usage
Sub.extend = Super.extend
Sub.mixin = Super.mixin
Sub.use = Super.use
// create asset registers, so extended classes
// can have their private assets too.
ASSET_TYPES.forEach(function (type) {
Sub[type] = Super[type]
})
// enable recursive self-lookup
if (name) {
Sub.options.components[name] = Sub
}
// keep a reference to the super options at extension time.
// later at instantiation we can check if Super's options have
// been updated.
Sub.superOptions = Super.options
Sub.extendOptions = extendOptions
Sub.sealedOptions = extend({}, Sub.options)
// cache constructor
cachedCtors[SuperId] = Sub
return Sub
}
}
function initProps(Comp: typeof Component) {
const props = Comp.options.props
for (const key in props) {
proxy(Comp.prototype, `_props`, key)
}
}
function initComputed(Comp: typeof Component) {
const computed = Comp.options.computed
for (const key in computed) {
defineComputed(Comp.prototype, key, computed[key])
}
}