exportfunctionmountComponent ( vm: Component, el: ?Element, hydrating?: boolean ): Component { vm.$el = el // 放一份el到自己的属性里 if (!vm.$options.render) { // render应该经过处理了, 因为我们经常都是用template或者vue文件 // 判断是否存在render函数, 如果没有就把render函数写成空VNode来避免红错, 并报出黄错 vm.$options.render = createEmptyVNode if (process.env.NODE_ENV !== 'production') { /* istanbul ignore if */ if ((vm.$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 (process.env.NODE_ENV !== 'production' && config.performance && mark) { // 不看这里的代码了, 直接看else里的, 行为是一样的 updateComponent = () => { const name = vm._name const id = vm._uid const startTag = `vue-perf-start:${id}` const endTag = `vue-perf-end:${id}`
// we set this to vm._watcher inside the watcher's constructor // since the watcher's initial patch may call $forceUpdate (e.g. inside child // component's mounted hook), which relies on vm._watcher being already defined // 注册一个Watcher newWatcher(vm, updateComponent, noop, null, true/* isRenderWatcher */) hydrating = false
// manually mounted instance, call mounted on self // mounted is called for render-created child components in its inserted hook if (vm.$vnode == null) { vm._isMounted = true callHook(vm, 'mounted') } return vm }
Vue.prototype._render = function (): VNode { constvm: Component = this const { render, _parentVnode } = vm.$options// todo: render和_parentVnode的由来
// reset _rendered flag on slots for duplicate slot check if (process.env.NODE_ENV !== 'production') { for (const key in vm.$slots) { // $flow-disable-line vm.$slots[key]._rendered = false } }
if (_parentVnode) { vm.$scopedSlots = _parentVnode.data.scopedSlots || emptyObject }
// set parent vnode. this allows render functions to have access // to the data on the placeholder node. vm.$vnode = _parentVnode // render self let vnode try { vnode = render.call(vm._renderProxy, vm.$createElement) } catch (e) { // catch其实不需要看了, 都是做异常处理, _vnode是在vm._update的时候保存的, 也就是上次的状态或是null(init的时候给的) handleError(e, vm, `render`) // return error render result, // or previous vnode to prevent render error causing blank component /* istanbul ignore else */ if (process.env.NODE_ENV !== 'production') { if (vm.$options.renderError) { try { vnode = vm.$options.renderError.call(vm._renderProxy, vm.$createElement, e) } catch (e) { handleError(e, vm, `renderError`) vnode = vm._vnode } } else { vnode = vm._vnode } } else { vnode = vm._vnode } } // return empty vnode in case the render function errored out if (!(vnode instanceofVNode)) { if (process.env.NODE_ENV !== 'production' && Array.isArray(vnode)) { warn( 'Multiple root nodes returned from render function. Render function ' + 'should return a single root node.', vm ) } vnode = createEmptyVNode() } // set parent vnode.parent = _parentVnode return vnode } }
Vue.prototype._update = function (vnode: VNode, hydrating?: boolean) { constvm: Component = this if (vm._isMounted) { callHook(vm, 'beforeUpdate') } // 记录update之前的状态 const prevEl = vm.$el const prevVnode = vm._vnode const prevActiveInstance = activeInstance activeInstance = vm vm._vnode = vnode // Vue.prototype.__patch__ is injected in entry points // based on the rendering backend used. if (!prevVnode) { // 初次加载, 只有_update方法更新vm._vnode, 初始化是null // initial render vm.$el = vm.__patch__( // patch创建新dom vm.$el, vnode, hydrating, false/* removeOnly */, vm.$options._parentElm, vm.$options._refElm ) // no need for the ref nodes after initial patch // this prevents keeping a detached DOM tree in memory (#5851) vm.$options._parentElm = vm.$options._refElm = null } else { // updates vm.$el = vm.__patch__(prevVnode, vnode) // patch更新dom } activeInstance = prevActiveInstance // update __vue__ reference if (prevEl) { prevEl.__vue__ = null } if (vm.$el) { vm.$el.__vue__ = vm } // if parent is an HOC, update its $el as well if (vm.$vnode && vm.$parent && vm.$vnode === vm.$parent._vnode) { vm.$parent.$el = vm.$el } // updated hook is called by the scheduler to ensure that children are // updated in a parent's updated hook. }
// public mount method Vue.prototype.$mount = function ( el?: string | Element, hydrating?: boolean ): Component { el = el && inBrowser ? query(el) : undefined returnmountComponent(this, el, hydrating) }
// web/entry-runtime-with-compiler.js 部分代码 const mount = Vue.prototype.$mount Vue.prototype.$mount = function ( el?: string | Element, hydrating?: boolean ): Component { el = el && query(el)
/* istanbul ignore if */ if (el === document.body || el === document.documentElement) { process.env.NODE_ENV !== 'production' && warn( `Do not mount Vue to <html> or <body> - mount to normal elements instead.` ) returnthis }
const options = this.$options // resolve template/el and convert to render function if (!options.render) { // 如果没有render方法就尝试把别的字段编译成render方法 let template = options.template if (template) { // 尝试template字段, 没有的话就获取el字段并编译成template if (typeof template === 'string') { if (template.charAt(0) === '#') { template = idToTemplate(template) /* istanbul ignore if */ if (process.env.NODE_ENV !== 'production' && !template) { warn( `Template element not found or is empty: ${options.template}`, this ) } } } elseif (template.nodeType) { template = template.innerHTML } else { if (process.env.NODE_ENV !== 'production') { warn('invalid template option:' + template, this) } returnthis } } elseif (el) { template = getOuterHTML(el) } if (template) { /* istanbul ignore if */ if (process.env.NODE_ENV !== 'production' && config.performance && mark) { mark('compile') }
