Memory leak when programmatically changing 'source' prop of Image

Description

If you use an Image component in render and use the parent component's state to manage the source prop, each time the source is changed the previous source is not deallocated. Even when the parent component is unmounted, the previous images still use memory.

Reproduction

I've made a simple ImageTest project that demonstrates the bug. (IMPORTANT: run app in release mode to experience the issue)

Code:

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  Image,
  TouchableHighlight,
  Dimensions,
} from 'react-native';

import image0 from './images/0.png'
import image1 from './images/1.png'
import image2 from './images/2.png'
import image3 from './images/3.png'
import image4 from './images/4.png'

const images = [
  image0,
  image1,
  image2,
  image3,
  image4,
]

export default class ImageTest extends Component {
  constructor() {
    super()

    this.state = ({
      counter: 0,
    })
  }

  increment = () => {
    this.setState({
      counter: this.state.counter + 1
    })
  }

  render() {
    const imageSource = images[this.state.counter]

    return (
      <View>
        <Image
          source={imageSource}
          style={styles.image}
        />
        <TouchableHighlight onPress={this.increment} style={styles.highlight}>
          <Text style={styles.text}>NEXT IMAGE</Text>
        </TouchableHighlight>
      </View>
    );
  }
}

const window = Dimensions.get('window')

const styles = StyleSheet.create({
  highlight: {
    backgroundColor: 'yellow',
    position: 'absolute',
    bottom: 0,
    left: 0,
  },
  text: {
    fontSize: 50,
  },
  image: {
    width: window.width,
    height: window.height,
  },
});

AppRegistry.registerComponent('ImageTest', () => ImageTest);

Solution

Presumably when the source is changed the underlying UIImage/UIImageView needs to be destroyed.

Additional Information

• React Native version: 0.41.0
• Platform: iOS
• Operating System: MacOS 10.12.3 / xcode 8.2

从链接的 ImageTest 复现开始，并在 iOS release mode 下运行它，在观察内存的同时更改 Image component 的 source prop。跟踪 Image component 对 source 更改的 native iOS 处理；完成标准是更改后以及 parent component 卸载后，之前的图像都会被释放。