vue 源码学习三

钩子函数的执行顺序

不使用keep-alive beforeRouteEnter –> created –> mounted –> destroyed

使用keep-alive beforeRouteEnter –> created –> mounted –> activated –> deactivated 再次进入缓存的页面，只会触发beforeRouteEnter –>activated –> deactivated 。 created和mounted不会再执行。

我们可以利用不同的钩子函数，做不同的事。

vue.component

template配置项的处理，与编译时的判断做对比

function _createElement (context,tag,data,children,normalizationType) {
  //这里省略一系列边界判断
  var vnode, ns;
  if (typeof tag === 'string') {
    var Ctor;
    ns = (context.$vnode && context.$vnode.ns) || config.getTagNamespace(tag);
    if (config.isReservedTag(tag)) { //标签名是一般的html标签
      vnode = new VNode(
        config.parsePlatformTagName(tag), data, children,
        undefined, undefined, context
      );
    } else if ((!data || !data.pre) && isDef(Ctor = resolveAsset(context.$options, 'components', tag))) { //标签名是组件标签名
      vnode = createComponent(Ctor, data, context, children, tag);
    } else {
      //未知或未列出的命名空间元素在运行时检查，
      //因为当其父项标准化子元素时可能会为其分配一个命名空间
      vnode = new VNode(
        tag, data, children,
        undefined, undefined, context
      );
    }
  } else {
    // direct component options / constructor
    vnode = createComponent(tag, data, context, children);
  }
  if (Array.isArray(vnode)) {
    return vnode
  } else if (isDef(vnode)) {
    if (isDef(ns)) { applyNS(vnode, ns); }
    if (isDef(data)) { registerDeepBindings(data); }
    return vnode
  } else {
    return createEmptyVNode()
  }
}
  function createFunctionalComponent (
    Ctor,
    propsData,
    data,
    contextVm,
    children
  ) {
    var options = Ctor.options;
    var props = {};
    var propOptions = options.props;
    if (isDef(propOptions)) {
      for (var key in propOptions) {
        props[key] = validateProp(key, propOptions, propsData || emptyObject);
      }
    } else {
      if (isDef(data.attrs)) { mergeProps(props, data.attrs); }
      if (isDef(data.props)) { mergeProps(props, data.props); }
    }

    var renderContext = new FunctionalRenderContext(
      data,
      props,
      children,
      contextVm,
      Ctor
    );

    var vnode = options.render.call(null, renderContext._c, renderContext);

    if (vnode instanceof VNode) {
      return cloneAndMarkFunctionalResult(vnode, data, renderContext.parent, options, renderContext)
    } else if (Array.isArray(vnode)) {
      var vnodes = normalizeChildren(vnode) || [];
      var res = new Array(vnodes.length);
      for (var i = 0; i < vnodes.length; i++) {
        res[i] = cloneAndMarkFunctionalResult(vnodes[i], data, renderContext.parent, options, renderContext);
      }
      return res
    }
  }

生命周期合并策略

var strats = config.optionMergeStrategies;
LIFECYCLE_HOOKS.forEach(function (hook) {
    strats[hook] = mergeHook;
  });
function mergeHook (
    parentVal,
    childVal
  ) {
    var res = childVal
      ? parentVal
        ? parentVal.concat(childVal)
        : Array.isArray(childVal)
          ? childVal
          : [childVal]
      : parentVal;
    return res
      ? dedupeHooks(res)
      : res
  }

function mergeOptions (
    parent,
    child,
    vm
  ) {
    {
      checkComponents(child);
    }

    if (typeof child === 'function') {
      child = child.options;
    }

    normalizeProps(child, vm);
    normalizeInject(child, vm);
    normalizeDirectives(child);

    // Apply extends and mixins on the child options,
    // but only if it is a raw options object that isn't
    // the result of another mergeOptions call.
    // Only merged options has the _base property.
    if (!child._base) {
      if (child.extends) {
        parent = mergeOptions(parent, child.extends, vm);
      }
      if (child.mixins) {
        for (var i = 0, l = child.mixins.length; i < l; i++) {
          parent = mergeOptions(parent, child.mixins[i], vm);
        }
      }
    }

    var options = {};
    var key;
    for (key in parent) {
      mergeField(key);
    }
    for (key in child) {
      if (!hasOwn(parent, key)) {
        mergeField(key);
      }
    }
    function mergeField (key) {
      var strat = strats[key] || defaultStrat;
      options[key] = strat(parent[key], child[key], vm, key);
    }
    return options
  }
 function initMixin$1 (Vue) {
    Vue.mixin = function (mixin) {
      this.options = mergeOptions(this.options, mixin);
      return this
    };
  }