Vue源码思维导图------------Vue选项的合并之$options

本节将看下初始化中的$options：

   Vue.prototype._init = function (options?: Object) {
     const vm: Component = this
     // a uid
     vm._uid = uid++

     // a flag to avoid this being observed
     vm._isVue = true
     // merge options
     if (options && options._isComponent) {
       // optimize internal component instantiation
       // since dynamic options merging is pretty slow, and none of the
       // internal component options needs special treatment.
       initInternalComponent(vm, options)
     } else {
15       vm.$options = mergeOptions(
16         // merge Vue.option
17         resolveConstructorOptions(vm.constructor),
18         // new Vue(data) data for object
19         options || {},
20         // current instance
21         vm
22       )
     }
 ………………………………
 }

通过上边的代码可以看到 ，初始化时vm.$options被mergeOptions方法赋值。那么mergeOptions又做了哪些事情呢？

一. 检查组件名称是否符合要求(  1.是否由字母和-组成，并且以字母开头；2.检测你所注册的组件是否是内置的标签)

   if (process.env.NODE_ENV !== 'production') {
     checkComponents(child)
   }

 /**
  * Validate component names
  */
 function checkComponents (options: Object) {
   for (const key in options.components) {
     validateComponentName(key)
   }
 }

 export function validateComponentName (name: string) {
   if (!/^[a-zA-Z][\w-]*$/.test(name)) {
     warn(
       'Invalid component name: "' + name + '". Component names ' +
       'can only contain alphanumeric characters and the hyphen, ' +
       'and must start with a letter.'
     )
   }
   if (isBuiltInTag(name) || config.isReservedTag(name)) {
     warn(
       'Do not use built-in or reserved HTML elements as component ' +
       'id: ' + name
     )
   }
 }

export const isBuiltInTag = makeMap('slot,component', true)

二.  规范化 （props, inject,directives）

1  normalizeProps(child, vm)
2  normalizeInject(child, vm)
3  normalizeDirectives(child)

 /**
  * Ensure all props option syntax are normalized into the
  * Object-based format.
  */
 function normalizeProps (options: Object, vm: ?Component) {
   const props = options.props
   if (!props) return
   const res = {}
   let i, val, name
   if (Array.isArray(props)) {
     i = props.length
     while (i--) {
       val = props[i]
       if (typeof val === 'string') {
         name = camelize(val)
         res[name] = { type: null }
       } else if (process.env.NODE_ENV !== 'production') {
         warn('props must be strings when using array syntax.')
       }
     }
   } else if (isPlainObject(props)) {
     for (const key in props) {
       val = props[key]
       name = camelize(key)
       res[name] = isPlainObject(val)
         ? val
         : { type: val }
     }
   } else if (process.env.NODE_ENV !== 'production') {
     warn(
       `Invalid value for option "props": expected an Array or an Object, ` +
       `but got ${toRawType(props)}.`,
       vm
     )
   }
   options.props = res
 }

 /**
  * Normalize all injections into Object-based format
  */
 function normalizeInject (options: Object, vm: ?Component) {
   const inject = options.inject
   if (!inject) return
   const normalized = options.inject = {}
   if (Array.isArray(inject)) {
     for (let i = 0; i < inject.length; i++) {
       normalized[inject[i]] = { from: inject[i] }
     }
   } else if (isPlainObject(inject)) {
     for (const key in inject) {
       const val = inject[key]
       normalized[key] = isPlainObject(val)
         ? extend({ from: key }, val)
         : { from: val }
     }
   } else if (process.env.NODE_ENV !== 'production') {
     warn(
       `Invalid value for option "inject": expected an Array or an Object, ` +
       `but got ${toRawType(inject)}.`,
       vm
     )
   }
 }

 /**
  * Normalize raw function directives into object format.
  */
 function normalizeDirectives (options: Object) {
   const dirs = options.directives
   if (dirs) {
     for (const key in dirs) {
       const def = dirs[key]
       if (typeof def === 'function') {
         dirs[key] = { bind: def, update: def }
       }
     }
   }
 }

三. Vue 选项的合并

   const options = {}
   let key
   for (key in parent) {
     mergeField(key)
   }
   for (key in child) {
     if (!hasOwn(parent, key)) {
       mergeField(key)
     }
   }
   function mergeField (key) {
     const strat = strats[key] || defaultStrat
     options[key] = strat(parent[key], child[key], vm, key)
   }

高清原图地址：https://github.com/huashuaipeng/vue--/blob/master/vm.%24options%20%EF%BC%88Vue%E5%AE%9E%E4%BE%8B%E4%B8%8A%E7%9A%84%24options%EF%BC%89.png

代码参考：

https://github.com/vuejs/vue/blob/dev/src/core/util/options.js

官网：

https://cn.vuejs.org/v2/api/#vm-options