Function initExtend

static/vuejs/vue.esm.js:3887–3967

(Vue)

/*  */

function initExtend (Vue) {
  /**
   * Each instance constructor, including Vue, has a unique
   * cid. This enables us to create wrapped "child
   * constructors" for prototypal inheritance and cache them.
   */
  Vue.cid = 0;
  var cid = 1;

  /**
   * Class inheritance
   */
  Vue.extend = function (extendOptions) {
    extendOptions = extendOptions || {};
    var Super = this;
    var SuperId = Super.cid;
    var cachedCtors = extendOptions._Ctor || (extendOptions._Ctor = {});
    if (cachedCtors[SuperId]) {
      return cachedCtors[SuperId]
    }

    var name = extendOptions.name || Super.options.name;
    if (process.env.NODE_ENV !== 'production') {
      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.'
        );
      }
    }

    var Sub = function VueComponent (options) {
      this._init(options);
    };
    Sub.prototype = Object.create(Super.prototype);
    Sub.prototype.constructor = Sub;
    Sub.cid = cid++;
    Sub.options = mergeOptions(
      Super.options,
      extendOptions
    );
    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;