Vue.mixin Vue.extend(Vue.component)的原理与…

 1    function Vue(options) {
 2         //调用_init方法
 3         this._init(options);
 4     }
 5 
 6 
 7 
 8     Vue.prototype._init = function (options) {
 9             var vm = this;
10             // a uid
11             vm._uid = uid$3++;
12 
13             var startTag, endTag;
14     
21             // a flag to avoid this being observed 标记该对象是一个Vue实例
22             vm._isVue = true;
23             // merge options
24             if (options && options._isComponent) { //组件实例化过程，即Vue.extend返回对象--稍后解释
25                 // optimize internal component instantiation
26                 // since dynamic options merging is pretty slow, and none of the
27                 // internal component options needs special treatment.
28                 initInternalComponent(vm, options);
29             } else {//将构造函数的options属性与实例化参数合并后付给实例的$options属性 ,该属性会在函数initState中进行初始化
30                 vm.$options = mergeOptions(  
31                     resolveConstructorOptions(vm.constructor),
32                     options || {},
33                     vm
34                 );
35             }
36             /* istanbul ignore else */
37             {
38                 initProxy(vm);
39             }
40             // expose real self
41             vm._self = vm;
42             initLifecycle(vm);
43             initEvents(vm);
44             initRender(vm);
45             callHook(vm, 'beforeCreate');
46             initInjections(vm); // resolve injections before data/props
47             initState(vm);
48             initProvide(vm); // resolve provide after data/props
49             callHook(vm, 'created');
50 
51             /* istanbul ignore if */
52             if ("development" !== 'production' && config.performance && mark) {
53                 vm._name = formatComponentName(vm, false);
54                 mark(endTag);
55                 measure(("vue " + (vm._name) + " init"), startTag, endTag);
56             }
57 
58             if (vm.$options.el) {
59                 vm.$mount(vm.$options.el);
60             }
61         };

 Vue.extend = function (extendOptions) {
            extendOptions = extendOptions || {};
            //将调用函数付给Super 
            var Super = this;  
            var SuperId = Super.cid;
            //如果参数中参入与创建的构造函数则直接返回
            var cachedCtors = extendOptions._Ctor || (extendOptions._Ctor = {});
            if (cachedCtors[SuperId]) {
                return cachedCtors[SuperId]
            }
            //获取组件的名称
            var name = extendOptions.name || Super.options.name;
            if ("development" !== 'production' && name) {
                validateComponentName(name);
            }
            //创建组件Sub
            var Sub = function VueComponent(options) {
                this._init(options);
            };
　　　　　　　//为组件添加对应的属性与方法
            Sub.prototype = Object.create(Super.prototype);
            Sub.prototype.constructor = Sub;
            Sub.cid = cid++;
            //合并super的options与extend的入参并赋值给Sub的options属性
            Sub.options = mergeOptions(
                Super.options,
                extendOptions
            );
            //在sub上保存Super的信息
            Sub['super'] = Super;

            // For props and computed properties, we define the proxy getters on
            // the Vue instances at extension time, on the extended prototype. This
            // avoids Object.defineProperty calls for each instance created.
            if (Sub.options.props) {
                initProps$1(Sub);
            }
            if (Sub.options.computed) {
                initComputed$1(Sub);
            }

            // allow further extension/mixin/plugin usage
            Sub.extend = Super.extend;
            Sub.mixin = Super.mixin;
            Sub.use = Super.use;

            // create asset registers, so extended classes
            // can have their private assets too.
            ASSET_TYPES.forEach(function (type) {
                Sub[type] = Super[type];
            });
            // enable recursive self-lookup
            //如果有组件名称，将该组件挂载到sub.options.components上。以便可在组件内使用

          if (name) { Sub.options.components[name] = Sub; } // keep a reference to the super options at extension time. // later at instantiation we can check if Super's options have // been updated.
             //保存option信息。以便在render的时候生成最新的options选项

            Sub.superOptions = Super.options;
            Sub.extendOptions = extendOptions;
            Sub.sealedOptions = extend({}, Sub.options);

            // cache constructor
            cachedCtors[SuperId] = Sub;
            return Sub  //返回sub构造函数
        };

 var ASSET_TYPES = [
        'component',
        'directive',
        'filter'
    ];
//定义  Vue.component .   Vue.directive  Vue.filter

ASSET_TYPES.forEach(function (type) {
            Vue[type] = function (
                id,
                definition
            ) {
                if (!definition) {
                    return this.options[type + 's'][id]
                } else {
                    /* istanbul ignore if */
                    if ("development" !== 'production' && type === 'component') {  
                        //对组件的命名规范进行验证
                        validateComponentName(id);
                    }
                    if (type === 'component' && isPlainObject(definition)) {
                       //如果第二个参数是一个Object 调用  Vue.extend(definition)生成一个构造函数   this.options._base === Vue
                        definition.name = definition.name || id;
                        definition = this.options._base.extend(definition);
                    }
                    if (type === 'directive' && typeof definition === 'function') {
                        definition = { bind: definition, update: definition };
                    }
                    //将Vue.options.components[id]赋值为 组件构造函数
                    this.options[type + 's'][id] = definition;
                    return definition
                }
            };
        });
    }