vue.js源码学习分享（八）

/*  */

var uid$1 = 0;

/**
 * A dep is an observable that can have multiple
 * directives subscribing（） to it.//一个dep 是一个可观察到的，dep能有多样的订阅指示
 */
var Dep = function Dep () {
  this.id = uid$1++;
  this.subs = [];
};

Dep.prototype.addSub = function addSub (sub) {
  this.subs.push(sub);
};

Dep.prototype.removeSub = function removeSub (sub) {
  remove(this.subs, sub);
};

Dep.prototype.depend = function depend () {
  if (Dep.target) {
    Dep.target.addDep(this);
  }
};

Dep.prototype.notify = function notify () {
  // stablize the subscriber list first
  var subs = this.subs.slice();
  for (var i = 0, l = subs.length; i < l; i++) {
    subs[i].update();
  }
};

// the current target watcher being evaluated.//当前的目标观察者被评估
// this is globally unique because there could be only one//这是全局唯一的因为这里只能只有一个
// watcher being evaluated at any time.观察者随时被观察
Dep.target = null;
var targetStack = [];

function pushTarget (_target) {
  if (Dep.target) { targetStack.push(Dep.target); }
  Dep.target = _target;
}

function popTarget () {
  Dep.target = targetStack.pop();
}

/*
 * not type checking this file because flow doesn't play well with//非类型检查这个文件，因为流不会很好的考虑动态的使用在数组原型上的方法
 * dynamically（动态） accessing（使用） methods on Array prototype
 */

var arrayProto = Array.prototype;
var arrayMethods = Object.create(arrayProto);
[
  'push',
  'pop',
  'shift',
  'unshift',
  'splice',
  'sort',
  'reverse'
]
.forEach(function (method) {
  // cache original method
  var original = arrayProto[method];
  def(arrayMethods, method, function mutator () {
    var arguments$1 = arguments;

    // avoid leaking arguments://避开arguments的漏洞
    // http://jsperf.com/closure-with-arguments
    var i = arguments.length;
    var args = new Array(i);
    while (i--) {
      args[i] = arguments$1[i];
    }
    var result = original.apply(this, args);
    var ob = this.__ob__;
    var inserted;
    switch (method) {
      case 'push':
        inserted = args;
        break
      case 'unshift':
        inserted = args;
        break
      case 'splice':
        inserted = args.slice(2);
        break
    }
    if (inserted) { ob.observeArray(inserted); }
    // notify change
    ob.dep.notify();
    return result
  });
});