How to call functions during Vue3 initialization

Vue3 initialization call function

createApp({}).mount(‘#app')

Entry file runtime-dom/src/index.tx

• ##createApp -> createRenderer -> createBaseRenderer (also created here render function and a series of rendering functions) -> createAppAPI (returns the real createApp method), returns the instance app,

• and then app.mount("#app" ) -> createVNode -> render(vnode,rootcontainier,isSVG) -> patch -> processComponent -> mountComponent (initial rendering) or updateComponent ->(createComponentInstance, setupComponent,setupRenderEffect)

• For setupComponent, whether there is a setup function or not, it will be handled separately. If there is, use the setup function to handle it. Initialize props and other parameters that need to be passed to the setup function. Call setup, setupComponent->finishComponentSetup (in This will handle the options initialization of version 2.x),

• For setupRenderEffect, execute a series of life hook functions, create rendering ReactiveEffect, and execute **effect.run()* *Method

is similar to vue2.x’s Watcher, computed, watch, componentUpdateFn also uses ReactiveEffect during the rendering process,

• ##setupRenderEffect

  will access the dependent response Variable

• watch(source,cb,options)

  will execute the function that accesses the source and collects dependencies

• watchEffect(fn)

  , will automatically execute fn to collect dependencies

##effect(fn, options)
• , where options has a lazy:true option , indicating not to execute the fn function immediately to collect dependencies, return a run function, call run() again, execute the fn function once, and collect dependencies

  // 1.计算属性
  // computed.ts
  // ComputedRefImpl类构造函数调用了new ReactiveEffect
  this.effect = new ReactiveEffect(getter, () => {
        if (!this._dirty) {
          this._dirty = true
          triggerRefValue(this)
        }
      })
      
  // 2. effect
  // effect.ts
  // effect函数中,可以接收第二个参数effect(fn,{lazy:true}),表示不立即执行
    const _effect = new ReactiveEffect(fn)
  // 3. apiWatch.ts doWatch方法
  // watch和watchEffect都是通过doWatch函数来,在这里调用new ReactiveEffect,然后根据不同情况执行effect.run(),对于watchEffect就是//执行器回调,对于watch就是访问监听的数据,然后收集依赖
    const effect = new ReactiveEffect(getter, scheduler)
  // 4. render.ts
  //在 setupRenderEffect中
  const effect = (instance.effect = new ReactiveEffect(
        componentUpdateFn,//更新组件函数
        () => queueJob(update),
        instance.scope // track it in component's effect scope
      ))

  Copy after login
  Vue3 program initialization process

mount

const Vue = {
	createApp(options) {
		//返回app实例
		return {
			mount(selector){
				// 获取渲染函数，编译结果
				// 渲染dom，追加到宿主元素
			}
			compile(template){
			//返回render
				return function render(){
					//描述视图
				}
			}
		}
	}
}

createApp

The two initialization functions exposed by Vue, createApp and createRenderer, the calling relationship between them

/*暴露给Vue的createApp*/
function createApp(options){
    const renderer =  Vue.createRenderer({
        /*定义一些平台特有的api，一些实例*/
        aaa(){},
        bbb(){}
    })
    /*用户调用的createApp，实际上是渲染器的createApp*/
    return renderer.createApp()
}
function createRenderer({aaa,bbb}){
    /*获得渲染器*/
    /*这个createApp是函数内部的*/
    return createApp(options){
        /*挂载逻辑*/
        return {
            /*返回App实例*/
        }
    }
}

In Vue3, the watcher was canceled and replaced with a side effect function. The side effect function will be re-executed every time the responsive data changes. The execution of the internal render function will trigger dependency collection, so that when the responsive data changes, the response The component will be updated.

PS: The difference from useEffect in react is that useEffect requires manual collection of dependencies, while effect() in Vue will automatically collect dependencies.

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