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realm on react native:未调试时无法获得结果

realm-js realm react-native android

Mujtaba Fadhil · 技术社区 · 6 年前

当 不调试 ,但当调试

另外,我注意到域的行为与wither调试的行为非常不同。

这只是一个想法的总结:

我在打印 object.constructor.name 查找对象的类型

调试时(远程使用chrome或safari):

let realm = new Realm(config);
realm.constructor.name --> will print (Realm)

let dogs = realm2.objects('Dog');
dogs.constructor.name --> will print (Results)

(inserting few dogs)

for (let oneDog of dogs) {
    oneDog.constructor.name --> will print (RealmObject)
} --> works perfectly

但如果不调试,一切就不同了:

let realm = new Realm(config);
realm.constructor.name --> will print (Object)

let dogs = realm2.objects('Dog');
dogs.constructor.name --> will print nothing

(inserting few dogs)

for (let oneDog of dogs) {
    oneDog.constructor.name --> not compiled
} --> will give the error below

TypeError: undefined is not a function (evaluating â_iterator[typeof
Symbol === âfunctionâ ? Symbol.iterator : â@@iteratorâ]()')

我不确定这是个错误还是我的代码有问题

领域和工具的版本

realm js-sdk版本:2.10.0
本机反应:0.55.4
客户端操作系统版本:在Android设备8.0上运行
哪个React Native调试器:chrome

完整代码:

import React, { Component } from 'react';
import { View, Text } from 'react-native';

const Realm = require('realm');

export default class Page3Screen extends Component {
  state = { messege : 'no messege' }

  componentWillMount() {
    const config = {
      schema: [{ name: 'Dog', properties: { name: 'string' } }],
    };
    let realm = new Realm(config);
    console.log(realm.constructor.name);
    this.setState({ messege: realm.constructor.name });

    realm.write(() => {
      realm.create('Dog', { name: 'Zozo' });
    });

    let dogs = realm.objects('Dog');
    // console.log(dogs.constructor.name);
    // this.setState({ messege: dogs.constructor.name });

    // for (let oneDog of dogs) {
    //    console.log(oneDog.constructor.name);
    //    this.setState({ messege: oneDog.constructor.name });
    // }
  }

  render() {
    return (
      <View style={{ alignSelf: 'stretch', flex: 1, alignItems: 'center', justifyContent: 'center' }}>
        <Text>{this.state.messege}</Text>
      </View>
    );
  }
}

2 回复 | 直到 6 年前

Mujtaba Fadhil 6 年前

我发现这个问题与 this issue

不管出于什么原因,安卓上的React原生版都在发布一个旧版本 jsc的一个版本,它不支持语言特性当前的react版本需要工作

解决方法是 updating the JSC version that ships with android ,但我使用了jsc版本 216113个 而不是最新的 明斯克版本17 而不是 21岁

以下是说明:

Follow steps below in order for your React Native app to use new version of JSC VM on android:

1. Add `jsc-android` to the "dependencies" section in your `package.json`:
```
dependencies {
+  "jsc-android": "^216113.0.0",
```

then run `npm install` or `yarn` (depending which npm client you use) in order for the new dependency to be installed in `node_modules`

2. Modify `andorid/build.gradle` file to add new local maven repository packaged in the `jsc-android` package to the search path:
```
allprojects {
    repositories {
        mavenLocal()
        jcenter()
        maven {
            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
            url "$rootDir/../node_modules/react-native/android"
        }
+       maven {
+           // Local Maven repo containing AARs with JSC library built for Android
+           url "$rootDir/../node_modules/jsc-android/android"
+       }
    }
}
```

3. Update your app's `build.gradle` file located in `android/app/build.gradle` to force app builds to use new version of the JSC library as opposed to the version specified in [react-native gradle module as a dependency](https://github.com/facebook/react-native/blob/e8df8d9fd579ff14224cacdb816f9ff07eef978d/ReactAndroid/build.gradle#L289):

```
}

+configurations.all {
+    resolutionStrategy {
+        force 'org.webkit:android-jsc:r216113'
+    }
+}

dependencies {
    compile fileTree(dir: "libs", include: ["*.jar"])
```

4. You're done, rebuild your app and enjoy updated version of JSC on android!

Soorena 6 年前

当你在里面的时候 debugging 模式下,react native在浏览器中而不是设备中运行js代码。既然你说它在浏览器上运行良好,但在设备上出现故障,我建议你检查以下内容:

检查设备是否连接到同一网络
运行此: adb reverse tcp:8081 tcp:8081
检查dev server是否正在运行,您可以使用以下命令运行它: $ react-native start
一些js特性需要在react native中使用polyfill,例如 Symbol 是的。因此,将以下内容添加到 index.js 以下内容:
```
import 'core-js/es6/symbol';
import 'core-js/fn/symbol/iterator';
```
在非常罕见的情况下,浏览器上的js引擎和android/ios设备之间存在差异

祝你好运。