vue.js 源代码学习笔记 ----- instance state

/* @flow */

import Dep from '../observer/dep'
import Watcher from '../observer/watcher'

import {
set,
del,
observe,
observerState,
defineReactive
} from '../observer/index'

import {
warn,
bind,
noop,
hasOwn,
isReserved,
handleError,
validateProp,
isPlainObject
} from '../util/index'

const sharedPropertyDefinition = {
enumerable: true,
configurable: true,
get: noop,
set: noop
}

export function proxy (target: Object, sourceKey: string, key: string) {
sharedPropertyDefinition.get = function proxyGetter () {
return this[sourceKey][key]
}
sharedPropertyDefinition.set = function proxySetter (val) {
this[sourceKey][key] = val
}
Object.defineProperty(target, key, sharedPropertyDefinition)
}

export function initState (vm: Component) {
vm._watchers = []
const opts = vm.$options
if (opts.props) initProps(vm, opts.props)
if (opts.methods) initMethods(vm, opts.methods)
if (opts.data) {
initData(vm)
} else {
observe(vm._data = {}, true /* asRootData */)
}
if (opts.computed) initComputed(vm, opts.computed)
if (opts.watch) initWatch(vm, opts.watch)
}

const isReservedProp = { key: 1, ref: 1, slot: 1 }

function initProps (vm: Component, propsOptions: Object) {
const propsData = vm.$options.propsData || {}
const props = vm._props = {}
// cache prop keys so that future props updates can iterate using Array
// instead of dynamic object key enumeration.
const keys = vm.$options._propKeys = []
const isRoot = !vm.$parent
// root instance props should be converted
observerState.shouldConvert = isRoot
for (const key in propsOptions) {
keys.push(key)
const value = validateProp(key, propsOptions, propsData, vm)
/* istanbul ignore else */
if (process.env.NODE_ENV !== 'production') {
if (isReservedProp[key]) {
warn(
`"${key}" is a reserved attribute and cannot be used as component prop.`,
vm
)
}
defineReactive(props, key, value, () => {
if (vm.$parent && !observerState.isSettingProps) {
warn(
`Avoid mutating a prop directly since the value will be ` +
`overwritten whenever the parent component re-renders. ` +
`Instead, use a data or computed property based on the prop's ` +
`value. Prop being mutated: "${key}"`,
vm
)
}
})
} else {
defineReactive(props, key, value)
}
// static props are already proxied on the component's prototype
// during Vue.extend(). We only need to proxy props defined at
// instantiation here.
if (!(key in vm)) {
proxy(vm, `_props`, key)
}
}
observerState.shouldConvert = true
}

function initData (vm: Component) {
let data = vm.$options.data
data = vm._data = typeof data === 'function'
? getData(data, vm)
: data || {}
if (!isPlainObject(data)) {
data = {}
process.env.NODE_ENV !== 'production' && warn(
'data functions should return an object:\n' +
'https://vuejs.org/v2/guide/components.html#data-Must-Be-a-Function',
vm
)
}
// proxy data on instance
const keys = Object.keys(data)
const props = vm.$options.props
let i = keys.length
while (i--) {
if (props && hasOwn(props, keys[i])) {
process.env.NODE_ENV !== 'production' && warn(
`The data property "${keys[i]}" is already declared as a prop. ` +
`Use prop default value instead.`,
vm
)
} else if (!isReserved(keys[i])) {
proxy(vm, `_data`, keys[i])
}
}
// observe data
observe(data, true /* asRootData */)
}

function getData (data: Function, vm: Component): any {
try {
return data.call(vm)
} catch (e) {
handleError(e, vm, `data()`)
return {}
}
}

const computedWatcherOptions = { lazy: true }

function initComputed (vm: Component, computed: Object) {
const watchers = vm._computedWatchers = Object.create(null)

for (const key in computed) {
const userDef = computed[key]
let getter = typeof userDef === 'function' ? userDef : userDef.get
if (process.env.NODE_ENV !== 'production') {
if (getter === undefined) {
warn(
`No getter function has been defined for computed property "${key}".`,
vm
)
getter = noop
}
}
// create internal watcher for the computed property.
watchers[key] = new Watcher(vm, getter, noop, computedWatcherOptions)

// component-defined computed properties are already defined on the
// component prototype. We only need to define computed properties defined
// at instantiation here.
if (!(key in vm)) {
defineComputed(vm, key, userDef)
}
}
}

export function defineComputed (target: any, key: string, userDef: Object | Function) {
if (typeof userDef === 'function') {
sharedPropertyDefinition.get = createComputedGetter(key)
sharedPropertyDefinition.set = noop
} else {
sharedPropertyDefinition.get = userDef.get
? userDef.cache !== false
? createComputedGetter(key)
: userDef.get
: noop
sharedPropertyDefinition.set = userDef.set
? userDef.set
: noop
}
Object.defineProperty(target, key, sharedPropertyDefinition)
}

function createComputedGetter (key) {
return function computedGetter () {
const watcher = this._computedWatchers && this._computedWatchers[key]
if (watcher) {
if (watcher.dirty) {
watcher.evaluate()
}
if (Dep.target) {
  watcher.depend()
}
return watcher.value
}
}
}

function initMethods (vm: Component, methods: Object) {
const props = vm.$options.props
for (const key in methods) {
vm[key] = methods[key] == null ? noop : bind(methods[key], vm)
if (process.env.NODE_ENV !== 'production') {
if (methods[key] == null) {
warn(
`method "${key}" has an undefined value in the component definition. ` +
`Did you reference the function correctly?`,
vm
)
}
if (props && hasOwn(props, key)) {
warn(
`method "${key}" has already been defined as a prop.`,
vm
)
}
}
}
}

function initWatch (vm: Component, watch: Object) {
for (const key in watch) {
const handler = watch[key]
if (Array.isArray(handler)) {
for (let i = 0; i < handler.length; i++) {
createWatcher(vm, key, handler[i])
}
} else {
createWatcher(vm, key, handler)
}
}
}

function createWatcher (vm: Component, key: string, handler: any) {
let options
if (isPlainObject(handler)) {
options = handler
handler = handler.handler
}
if (typeof handler === 'string') {
handler = vm[handler]
}
vm.$watch(key, handler, options)
}

export function stateMixin (Vue: Class<Component>) {
// flow somehow has problems with directly declared definition object
// when using Object.defineProperty, so we have to procedurally build up
// the object here.
const dataDef = {}
dataDef.get = function () { return this._data }
const propsDef = {}
propsDef.get = function () { return this._props }
if (process.env.NODE_ENV !== 'production') {
dataDef.set = function (newData: Object) {
warn(
'Avoid replacing instance root $data. ' +
'Use nested data properties instead.',
this
)
}
propsDef.set = function () {
warn(`$props is readonly.`, this)
}
}
Object.defineProperty(Vue.prototype, '$data', dataDef)
Object.defineProperty(Vue.prototype, '$props', propsDef)

Vue.prototype.$set = set
Vue.prototype.$delete = del

Vue.prototype.$watch = function (
expOrFn: string | Function,
cb: Function,
options?: Object
): Function {
const vm: Component = this
options = options || {}
options.user = true
const watcher = new Watcher(vm, expOrFn, cb, options)
if (options.immediate) {
cb.call(vm, watcher.value)
}
return function unwatchFn () {
watcher.teardown()
}
}
}