TypeScript ember-meta.descriptorFor函数代码示例

/**
  This function is called just after an object property has changed.
  It will notify any observers and clear caches among other things.

  Normally you will not need to call this method directly but if for some
  reason you can't directly watch a property you can invoke this method
  manually.

  @method notifyPropertyChange
  @for Ember
  @param {Object} obj The object with the property that will change
  @param {String} keyName The property key (or path) that will change.
  @param {Meta} meta The objects meta.
  @return {void}
  @private
*/
function notifyPropertyChange(obj: object, keyName: string, _meta?: Meta): void {
  let meta = _meta === undefined ? peekMeta(obj) : _meta;
  let hasMeta = meta !== undefined;

  if (hasMeta && !meta.isInitialized(obj)) {
    return;
  }

  let possibleDesc = descriptorFor(obj, keyName, meta);

  if (possibleDesc !== undefined && typeof possibleDesc.didChange === 'function') {
    possibleDesc.didChange(obj, keyName);
  }

  if (hasMeta && meta.peekWatching(keyName) > 0) {
    dependentKeysDidChange(obj, keyName, meta);
    chainsDidChange(obj, keyName, meta);
    notifyObservers(obj, keyName, meta);
  }

  if (PROPERTY_DID_CHANGE in obj) {
    obj[PROPERTY_DID_CHANGE](keyName);
  }

  if (hasMeta) {
    if (meta.isSourceDestroying()) {
      return;
    }
    markObjectAsDirty(obj, keyName, meta);
  }

  if (DEBUG) {
    assertNotRendered(obj, keyName);
  }
}

function applyMixin(obj: { [key: string]: any }, mixins: Mixin[], partial: boolean) {
  let descs = {};
  let values = {};
  let meta = metaFor(obj);
  let keys: string[] = [];
  let key, value, desc;

  (obj as any)._super = ROOT;

  // Go through all mixins and hashes passed in, and:
  //
  // * Handle concatenated properties
  // * Handle merged properties
  // * Set up _super wrapping if necessary
  // * Set up computed property descriptors
  // * Copying `toString` in broken browsers
  mergeMixins(mixins, meta, descs, values, obj, keys);

  for (let i = 0; i < keys.length; i++) {
    key = keys[i];
    if (key === 'constructor' || !values.hasOwnProperty(key)) {
      continue;
    }

    desc = descs[key];
    value = values[key];

    while (desc && desc instanceof Alias) {
      let followed = followAlias(obj, desc, descs, values);
      desc = followed.desc;
      value = followed.value;
    }

    if (desc === undefined && value === undefined) {
      continue;
    }

    if (descriptorFor(obj, key) !== undefined) {
      replaceObserversAndListeners(obj, key, null, value);
    } else {
      replaceObserversAndListeners(obj, key, obj[key], value);
    }

    if (
      ENV._ENABLE_BINDING_SUPPORT &&
      typeof Mixin.detectBinding === 'function' &&
      Mixin.detectBinding(key)
    ) {
      meta.writeBindings(key, value);
    }

    defineProperty(obj, key, desc, value, meta);
  }

  if (ENV._ENABLE_BINDING_SUPPORT && !partial && typeof Mixin.finishPartial === 'function') {
    Mixin.finishPartial(obj, meta);
  }

  return obj;
}

function giveMethodSuper(
  obj: object,
  key: string,
  method: Function,
  values: { [key: string]: any },
  descs: { [key: string]: any }
) {
  // Methods overwrite computed properties, and do not call super to them.
  if (descs[key] !== undefined) {
    return method;
  }

  // Find the original method in a parent mixin
  let superMethod = values[key];

  // If we didn't find the original value in a parent mixin, find it in
  // the original object
  if (superMethod === undefined && descriptorFor(obj, key) === undefined) {
    superMethod = obj[key];
  }

  // Only wrap the new method if the original method was a function
  if (typeof superMethod === 'function') {
    return wrap(method, superMethod);
  }

  return method;
}

  meta.forEachInDeps(depKey, (key: string) => {
    possibleDesc = descriptorFor(obj, key, meta);

    if (possibleDesc !== undefined && possibleDesc._suspended === obj) {
      return;
    }

    method(obj, key, meta);
  });

function injectedPropertyGet(this: any, keyName: string): any {
  let desc = descriptorFor(this, keyName);
  let owner = getOwner(this) || this.container; // fallback to `container` for backwards compat

  assert(
    `InjectedProperties should be defined with the inject computed property macros.`,
    desc && desc.type
  );
  assert(
    `Attempting to lookup an injected property on an object without a container, ensure that the object was instantiated via a container.`,
    !!owner
  );

  let specifier = `${desc.type}:${desc.name || keyName}`;
  return owner.lookup(specifier, {
    source: desc.source,
    namespace: desc.namespace,
  });
}

function giveDescriptorSuper(
  meta: Meta,
  key: string,
  property: ComputedProperty,
  values: { [key: string]: any },
  descs: { [key: string]: any },
  base: object
): ComputedProperty {
  let superProperty;

  // Computed properties override methods, and do not call super to them
  if (values[key] === undefined) {
    // Find the original descriptor in a parent mixin
    superProperty = descs[key];
  }

  // If we didn't find the original descriptor in a parent mixin, find
  // it on the original object.
  if (!superProperty) {
    superProperty = descriptorFor(base, key, meta);
  }

  if (superProperty === undefined || !(superProperty instanceof ComputedProperty)) {
    return property;
  }

  // Since multiple mixins may inherit from the same parent, we need
  // to clone the computed property so that other mixins do not receive
  // the wrapped version.
  property = Object.create(property);
  property._getter = wrap(property._getter, superProperty._getter) as ComputedPropertyGetter;
  if (superProperty._setter) {
    if (property._setter) {
      property._setter = wrap(property._setter, superProperty._setter) as ComputedPropertySetter;
    } else {
      property._setter = superProperty._setter;
    }
  }

  return property;
}

function followAlias(
  obj: object,
  desc: any,
  descs: { [key: string]: any },
  values: { [key: string]: any }
) {
  let altKey = desc.methodName;
  let value;
  let possibleDesc;
  if (descs[altKey] || values[altKey]) {
    value = values[altKey];
    desc = descs[altKey];
  } else if ((possibleDesc = descriptorFor(obj, altKey)) !== undefined) {
    desc = possibleDesc;
    value = undefined;
  } else {
    desc = undefined;
    value = obj[altKey];
  }

  return { desc, value };
}

export function watchKey(obj: object, keyName: string, _meta?: Meta) {
  let meta = _meta === undefined ? metaFor(obj) : _meta;
  let count = meta.peekWatching(keyName);
  meta.writeWatching(keyName, count + 1);

  if (count === 0) {
    // activate watching first time
    let possibleDesc = descriptorFor(obj, keyName, meta);

    if (possibleDesc !== undefined && possibleDesc.willWatch !== undefined) {
      possibleDesc.willWatch(obj, keyName, meta);
    }

    if (typeof (obj as MaybeHasWillWatchProperty).willWatchProperty === 'function') {
      (obj as MaybeHasWillWatchProperty).willWatchProperty!(keyName);
    }

    if (DEBUG) {
      // NOTE: this is dropped for prod + minified builds
      handleMandatorySetter(meta, obj, keyName);
    }
  }
}

export function unwatchKey(obj: object, keyName: string, _meta?: Meta) {
  let meta = _meta === undefined ? peekMeta(obj) : _meta;

  // do nothing of this object has already been destroyed
  if (meta === undefined || meta.isSourceDestroyed()) {
    return;
  }

  let count = meta.peekWatching(keyName);
  if (count === 1) {
    meta.writeWatching(keyName, 0);

    let possibleDesc = descriptorFor(obj, keyName, meta);
    let isDescriptor = possibleDesc !== undefined;

    if (isDescriptor && possibleDesc.didUnwatch !== undefined) {
      possibleDesc.didUnwatch(obj, keyName, meta);
    }

    if (typeof (obj as MaybeHasDidUnwatchProperty).didUnwatchProperty === 'function') {
      (obj as MaybeHasDidUnwatchProperty).didUnwatchProperty!(keyName);
    }

    if (DEBUG) {
      // It is true, the following code looks quite WAT. But have no fear, It
      // exists purely to improve development ergonomics and is removed from
      // ember.min.js and ember.prod.js builds.
      //
      // Some further context: Once a property is watched by ember, bypassing `set`
      // for mutation, will bypass observation. This code exists to assert when
      // that occurs, and attempt to provide more helpful feedback. The alternative
      // is tricky to debug partially observable properties.
      if (!isDescriptor && keyName in obj) {
        let maybeMandatoryDescriptor = lookupDescriptor(obj, keyName);

        if (
          maybeMandatoryDescriptor &&
          maybeMandatoryDescriptor.set &&
          (maybeMandatoryDescriptor.set as MandatorySetterFunction).isMandatorySetter
        ) {
          if (
            maybeMandatoryDescriptor.get &&
            (maybeMandatoryDescriptor.get as InheritingGetterFunction).isInheritingGetter
          ) {
            let possibleValue = meta.readInheritedValue('values', keyName);
            if (possibleValue === UNDEFINED) {
              delete obj[keyName];
              return;
            }
          }

          Object.defineProperty(obj, keyName, {
            configurable: true,
            enumerable: Object.prototype.propertyIsEnumerable.call(obj, keyName),
            writable: true,
            value: meta.peekValues(keyName),
          });
          meta.deleteFromValues(keyName);
        }
      }
    }
  } else if (count > 1) {
    meta.writeWatching(keyName, count - 1);
  }
}

export function defineProperty(
  obj: object,
  keyName: string,
  desc: Descriptor | undefined | null,
  data?: any | undefined | null,
  meta?: Meta
) {
  if (meta === undefined) {
    meta = metaFor(obj);
  }

  let watching = meta.peekWatching(keyName) > 0;
  let previousDesc = descriptorFor(obj, keyName, meta);
  let wasDescriptor = previousDesc !== undefined;

  if (wasDescriptor) {
    previousDesc.teardown(obj, keyName, meta);
    meta.removeDescriptors(keyName);
  }

  // used to track if the the property being defined be enumerable
  let enumerable = true;

  // Ember.NativeArray is a normal Ember.Mixin that we mix into `Array.prototype` when prototype extensions are enabled
  // mutating a native object prototype like this should _not_ result in enumerable properties being added (or we have significant
  // issues with things like deep equality checks from test frameworks, or things like jQuery.extend(true, [], [])).
  //
  // this is a hack, and we should stop mutating the array prototype by default 😫
  if (obj === Array.prototype) {
    enumerable = false;
  }

  let value;
  if (desc instanceof Descriptor) {
    value = desc;

    Object.defineProperty(obj, keyName, {
      configurable: true,
      enumerable,
      get: DESCRIPTOR_GETTER_FUNCTION(keyName, value),
    });

    meta.writeDescriptors(keyName, value);

    desc.setup(obj, keyName);
  } else if (desc === undefined || desc === null) {
    value = data;

    if (DEBUG && watching) {
      meta.writeValues(keyName, data);

      let defaultDescriptor = {
        configurable: true,
        enumerable,
        set: MANDATORY_SETTER_FUNCTION(keyName),
        get: DEFAULT_GETTER_FUNCTION(keyName),
      };

      Object.defineProperty(obj, keyName, defaultDescriptor);
    } else if (wasDescriptor || enumerable === false) {
      Object.defineProperty(obj, keyName, {
        configurable: true,
        enumerable,
        writable: true,
        value,
      });
    } else {
      obj[keyName] = data;
    }
  } else {
    value = desc;

    // fallback to ES5
    Object.defineProperty(obj, keyName, desc);
  }

  // if key is being watched, override chains that
  // were initialized with the prototype
  if (watching) {
    overrideChains(obj, keyName, meta);
  }

  // The `value` passed to the `didDefineProperty` hook is
  // either the descriptor or data, whichever was passed.
  if (typeof (obj as ExtendedObject).didDefineProperty === 'function') {
    (obj as ExtendedObject).didDefineProperty!(obj, keyName, value);
  }
}