官方实现
2023年06月11日
一、src/platforms/web/runtime-with-compiler.ts $mount
/**
* 编译器的入口
* 运行时的 Vue.js 包就没有这部分的代码，通过 打包器 结合 vue-loader + vue-compiler-utils 进行预编译，将模版编译成 render 函数
*
* 就做了一件事情，得到组件的渲染函数，将其设置到 this.$options 上
*/
const mount = Vue.prototype.$mount
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
): Component {
// 挂载点
el = el && query(el)
// 挂载点不能是 body 或者 html
if (el === document.body || el === document.documentElement) {
__DEV__ &&
warn(
`Do not mount Vue to <html> or <body> - mount to normal elements instead.`
)
return this
}
// 配置项
const options = this.$options
/**
* 如果用户提供了 render 配置项，则直接跳过编译阶段，否则进入编译阶段
* 解析 template 和 el，并转换为 render 函数
* 优先级：render > template > el
*/
if (!options.render) {
let template = options.template
// 处理 template 选项
if (template) {
if (typeof template === 'string') {
if (template.charAt(0) === '#') {
// { template: '#app' }，template 是一个 id 选择器，则获取该元素的 innerHtml 作为模版
template = idToTemplate(template)
/* istanbul ignore if */
if (__DEV__ && !template) {
warn(
`Template element not found or is empty: ${options.template}`,
this
)
}
}
} else if (template.nodeType) {
// template 是一个正常的元素，获取其 innerHtml 作为模版
template = template.innerHTML
} else {
if (__DEV__) {
warn('invalid template option:' + template, this)
}
return this
}
} else if (el) {
// 设置了 el 选项，获取 el 选择器的 outerHtml 作为模版
template = getOuterHTML(el)
}
if (template) {
// 模版就绪，进入编译阶段
/* istanbul ignore if */
if (__DEV__ && config.performance && mark) {
mark('compile')
}
// 编译模版，得到 动态渲染函数和静态渲染函数
const { render, staticRenderFns } = compileToFunctions(
template,
{
// 在非生产环境下，编译时记录标签属性在 模版字符串中开始和结束的位置索引
outputSourceRange: __DEV__,
shouldDecodeNewlines,
shouldDecodeNewlinesForHref,
// 界定符，默认 {{}}
delimiters: options.delimiters,
// 是否保留注释
comments: options.comments
},
this
)
// 将两个渲染函数放到 this.$options 上
options.render = render
options.staticRenderFns = staticRenderFns
/* istanbul ignore if */
if (__DEV__ && config.performance && mark) {
mark('compile end')
measure(`vue ${this._name} compile`, 'compile', 'compile end')
}
}
}
// 执行挂载
return mount.call(this, el, hydrating)
}
二、src/platforms/web/runtime/index.ts $mount()
// public mount method
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
): Component {
el = el && inBrowser ? query(el) : undefined
return mountComponent(this, el, hydrating)
}
三、src/core/instance/lifecycle.ts mountComponent()
export function mountComponent(
vm: Component,
el: Element | null | undefined,
hydrating?: boolean
): Component {
vm.$el = el
if (!vm.$options.render) {
// @ts-expect-error invalid type
vm.$options.render = createEmptyVNode
if (__DEV__) {
/* istanbul ignore if */
if (
(vm.$options.template && vm.$options.template.charAt(0) !== '#') ||
vm.$options.el ||
el
) {
warn(
'You are using the runtime-only build of Vue where the template ' +
'compiler is not available. Either pre-compile the templates into ' +
'render functions, or use the compiler-included build.',
vm
)
} else {
warn(
'Failed to mount component: template or render function not defined.',
vm
)
}
}
}
callHook(vm, 'beforeMount')
let updateComponent
/* istanbul ignore if */
if (__DEV__ && config.performance && mark) {
updateComponent = () => {
const name = vm._name
const id = vm._uid
const startTag = `vue-perf-start:${id}`
const endTag = `vue-perf-end:${id}`
mark(startTag)
const vnode = vm._render()
mark(endTag)
measure(`vue ${name} render`, startTag, endTag)
mark(startTag)
vm._update(vnode, hydrating)
mark(endTag)
measure(`vue ${name} patch`, startTag, endTag)
}
} else {
updateComponent = () => {
vm._update(vm._render(), hydrating)
}
}
const watcherOptions: WatcherOptions = {
before() {
if (vm._isMounted && !vm._isDestroyed) {
callHook(vm, 'beforeUpdate')
}
}
}
if (__DEV__) {
watcherOptions.onTrack = e => callHook(vm, 'renderTracked', [e])
watcherOptions.onTrigger = e => callHook(vm, 'renderTriggered', [e])
}
// we set this to vm._watcher inside the watcher's constructor
// since the watcher's initial patch may call $forceUpdate (e.g. inside child
// component's mounted hook), which relies on vm._watcher being already defined
new Watcher(
vm,
updateComponent,
noop,
watcherOptions,
true /* isRenderWatcher */
)
hydrating = false
// flush buffer for flush: "pre" watchers queued in setup()
const preWatchers = vm._preWatchers
if (preWatchers) {
for (let i = 0; i < preWatchers.length; i++) {
preWatchers[i].run()
}
}
// manually mounted instance, call mounted on self
// mounted is called for render-created child components in its inserted hook
if (vm.$vnode == null) {
vm._isMounted = true
callHook(vm, 'mounted')
}
return vm
}
四、src/core/instance/lifecycle.ts _update()
Vue.prototype._update = function (vnode: VNode, hydrating?: boolean) {
const vm: Component = this
const prevEl = vm.$el
const prevVnode = vm._vnode
const restoreActiveInstance = setActiveInstance(vm)
vm._vnode = vnode
// Vue.prototype.__patch__ is injected in entry points
// based on the rendering backend used.
if (!prevVnode) {
// initial render
vm.$el = vm.__patch__(vm.$el, vnode, hydrating, false /* removeOnly */)
} else {
// updates
vm.$el = vm.__patch__(prevVnode, vnode)
}
restoreActiveInstance()
// update __vue__ reference
if (prevEl) {
prevEl.__vue__ = null
}
if (vm.$el) {
vm.$el.__vue__ = vm
}
// if parent is an HOC, update its $el as well
let wrapper: Component | undefined = vm
while (
wrapper &&
wrapper.$vnode &&
wrapper.$parent &&
wrapper.$vnode === wrapper.$parent._vnode
) {
wrapper.$parent.$el = wrapper.$el
wrapper = wrapper.$parent
}
// updated hook is called by the scheduler to ensure that children are
// updated in a parent's updated hook.
}