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130 lines
5.8 KiB
Markdown
130 lines
5.8 KiB
Markdown
Redux DevTools
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=========================
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A live-editing time travel environment for [Redux](https://github.com/rackt/redux).
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**[See Dan's React Europe talk demoing it!](http://youtube.com/watch?v=xsSnOQynTHs)**
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### Features
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* Lets you inspect every state and action payload
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* Lets you go back in time by “cancelling” actions
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* If you change the reducer code, each “staged” action will be re-evaluted
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* If the reducers throw, you will see during which action this happened, and what the error was
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* With `persistState()` store enhancer, you can persist debug sessions across page reloads
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* To monitor a part of the state, you can set a `select` prop on the DevTools component: `<DevTools select={state => state.todos} store={store} monitor={LogMonitor} />`
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### Installation
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```
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npm install --save-dev redux-devtools
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```
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DevTools is a [store enhancer](http://rackt.github.io/redux/docs/Glossary.html#store-enhancer), which should be added to your middleware stack *after* [`applyMiddleware`](http://rackt.github.io/redux/docs/api/applyMiddleware.html) as `applyMiddleware` is potentially asynchronous. Otherwise, DevTools won’t see the raw actions emitted by asynchronous middleware such as [redux-promise](https://github.com/acdlite/redux-promise) or [redux-thunk](https://github.com/gaearon/redux-thunk).
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To install, firstly import `devTools` into your root React component:
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```js
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// Redux utility functions
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import { compose, createStore, applyMiddleware } from 'redux';
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// Redux DevTools store enhancers
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import { devTools, persistState } from 'redux-devtools';
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// React components for Redux DevTools
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import { DevTools, DebugPanel, LogMonitor } from 'redux-devtools/lib/react';
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```
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Then, add `devTools` to your store enhancers, and create your store:
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```js
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const finalCreateStore = compose(
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// Enables your middleware:
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applyMiddleware(thunk),
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// Provides support for DevTools:
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devTools(),
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// Lets you write ?debug_session=<name> in address bar to persist debug sessions
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persistState(window.location.href.match(/[?&]debug_session=([^&]+)\b/)),
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createStore
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);
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const store = finalCreateStore(reducer);
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```
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Finally, include the `DevTools` in your page. You may pass either `LogMonitor` (the default one) or any of the custom monitors described below. For convenience, you can use `DebugPanel` to dock `DevTools` to some part of the screen, but you can put it also somewhere else in the component tree.
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```js
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export default class Root extends Component {
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render() {
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return (
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<div>
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<Provider store={store}>
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{() => <CounterApp />}
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</Provider>
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<DebugPanel top right bottom>
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<DevTools store={store} monitor={LogMonitor} />
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</DebugPanel>
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</div>
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);
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}
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}
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```
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[This commit](https://github.com/gaearon/redux-devtools/commit/0a2a97556e252bfad822ca438923774bc8b932a4) should give you an idea about how to add Redux DevTools for your app **but make sure to only apply `devTools()` in development!** In production, this will be terribly slow because actions just accumulate forever. (We'll need to implement a rolling window for dev too.)
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For example, in Webpack, you can use `DefinePlugin` to turn magic constants like `__DEV__` into `true` or `false` depending on the environment, and import and render `redux-devtools` conditionally behind `if (__DEV__)`. Then, if you have an Uglify step before production, Uglify will eliminate dead `if (false)` branches with `redux-devtools` imports. Here is [an example](https://github.com/erikras/react-redux-universal-hot-example/compare/66bf63fb0f23a3c264a5d37c3acb4c047bf0c0c9...c6515236a1def8a3d2bfeb8f6cd6f0ccdb2f9e1b) of adding React DevTools to a project handling the production case correctly.
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### Running Examples
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You can do this:
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```
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git clone https://github.com/gaearon/redux-devtools.git
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cd redux-devtools
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npm install
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cd examples/counter
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npm install
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npm start
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open http://localhost:3000
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```
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Try clicking on actions in the log, or changing some code inside `examples/counter/reducers/counter`.
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For fun, you can also open `http://localhost:3000/?debug_session=123`, click around, and then refresh.
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Oh, and you can do the same with the TodoMVC example as well.
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### Custom Monitors
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**You can build a completely custom UI for it** because `<DevTools>` accepts a `monitor` React component prop. The included `LogMonitor` is just an example.
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**[I challenge you to build a custom monitor for Redux DevTools!](https://github.com/gaearon/redux-devtools/issues/3)**
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Some crazy ideas for custom monitors:
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* A slider that lets you jump between computed states just by dragging it
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* An in-app layer that shows the last N states right in the app (e.g. for animation)
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* A time machine like interface where the last N states of your app reside on different Z layers
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* Feel free to come up with and implement your own! Check `LogMonitor` propTypes to see what you can do.
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In fact some of these are implemented already:
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#### [redux-devtools-diff-monitor](https://github.com/whetstone/redux-devtools-diff-monitor)
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#### [redux-slider-monitor](https://github.com/calesce/redux-slider-monitor)
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#### [redux-devtools-gentest-plugin](https://github.com/lapanoid/redux-devtools-gentest-plugin)
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#### Keep them coming!
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Create a PR to add your custom monitor.
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### License
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MIT
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