animated/src/AnimatedInterpolation.js

Declarative Animations Library for React and React Native

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @flow
 */
'use strict';

var Animated = require('./Animated');
var AnimatedWithChildren = require('./AnimatedWithChildren');
var invariant = require('invariant');
var Interpolation = require('./Interpolation');
var guid = require('./guid');

import type { ValueListenerCallback } from './AnimatedValue';

class AnimatedInterpolation extends AnimatedWithChildren {
  _parent: Animated;
  _interpolation: (input: number) => number | string;
  _listeners: {[key: number]: ValueListenerCallback};
  _parentListener: number;

  constructor(parent: Animated, interpolation: (input: number) => number | string) {
    super();
    this._parent = parent;
    this._interpolation = interpolation;
    this._listeners = {};
  }

  __getValue(): number | string {
    var parentValue: number = this._parent.__getValue();
    invariant(
      typeof parentValue === 'number',
      'Cannot interpolate an input which is not a number.'
    );
    return this._interpolation(parentValue);
  }

  addListener(callback: ValueListenerCallback): string {
    if (!this._parentListener) {
      this._parentListener = this._parent.addListener(() => {
        for (var key in this._listeners) {
          this._listeners[key]({value: this.__getValue()});
        }
      })
    }
    var id = guid();
    this._listeners[id] = callback;
    return id;
  }

  removeListener(id: string): void {
    delete this._listeners[id];
  }

  interpolate(config: InterpolationConfigType): AnimatedInterpolation {
    return new AnimatedInterpolation(this, Interpolation.create(config));
  }

  __attach(): void {
    this._parent.__addChild(this);
  }

  __detach(): void {
    this._parent.__removeChild(this);
    this._parentListener = this._parent.removeListener(this._parentListener);
  }
}

module.exports = AnimatedInterpolation;