Allow injection of a batching function to wrap dispatches

React automatically batches updates when inside a synthetic event handler, but asynchronous updates do not get the same treatment. Consider the following scenario: 1. A button in ComponentA calls an action creator 2. The action creator calls an async API 3. As a result of the async call, the action creator dispatches an action 4. That action sets new state in a store 5. The new store data causes a new child to be mounted inside ComponentA (let's call it ComponentB) 6. ComponentB fires an action immediately, via componentDid/WillMount Unlike re-renders from synchronous action dispatches (which generally happen in the context of a synthetic event), asynchronous dispatches aren't called within the context of React's batching strategy. This means the dispatch loop is still in progress when ComponentB mounts, causing a cascading dispatch exception. `Flux#setBatchingFunction` allows you to pass a batching function to wrap dispatches in; in most (all?) cases, you'll want to pass `React.addons.batchedUpdates` in order to force all dispatches to happen in the context of React's batched updates. Fixes #92
BinaryMuse · Apr 5, 2015 · 7e32577 · 7e32577 · ruswerner · Jun 16, 2015
1 parent 123aec6
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diff --git a/lib/dispatcher.js b/lib/dispatcher.js
@@ -9,11 +9,16 @@ var _clone = require("lodash-node/modern/lang/clone"),
     _findKey = require("lodash-node/modern/object/findKey"),
     _uniq = require("lodash-node/modern/array/uniq");
 
+var defaultBatchingFunction = function(callback) {
+  callback();
+};
+
 var Dispatcher = function(stores) {
   this.stores = {};
   this.currentDispatch = null;
   this.currentActionType = null;
   this.waitingToDispatch = [];
+  this.batchingFunction = defaultBatchingFunction;
 
   for (var key in stores) {
     if (stores.hasOwnProperty(key)) {
@@ -28,6 +33,12 @@ Dispatcher.prototype.addStore = function(name, store) {
 };
 
 Dispatcher.prototype.dispatch = function(action) {
+  this.batchingFunction(function() {
+    this._dispatch(action);
+  }.bind(this));
+};
+
+Dispatcher.prototype._dispatch = function(action) {
   if (!action || !action.type) {
     throw new Error("Can only dispatch actions with a 'type' property");
   }
@@ -141,4 +152,12 @@ Dispatcher.prototype.waitForStores = function(store, stores, fn) {
   dispatch.waitCallback = fn;
 };
 
+Dispatcher.prototype.setBatchingFunction = function(fn) {
+  if (fn) {
+    this.batchingFunction = fn;
+  } else {
+    this.batchingFunction = defaultBatchingFunction;
+  }
+};
+
 module.exports = Dispatcher;
diff --git a/lib/flux.js b/lib/flux.js
@@ -116,4 +116,8 @@ Flux.prototype.addStores = function(stores) {
   }
 };
 
+Flux.prototype.setBatchingFunction = function(fn) {
+  this.dispatcher.setBatchingFunction(fn);
+};
+
 module.exports = Flux;
diff --git a/test/unit/test_batched_updates.js b/test/unit/test_batched_updates.js
@@ -0,0 +1,139 @@
+var Fluxxor = require("../../"),
+    jsdom = require("jsdom");
+
+var chai = require("chai"),
+    expect = chai.expect;
+
+var Store = Fluxxor.createStore({
+  actions: {
+    "ACTIVATE": "handleActivate",
+    "LOAD_INITIAL_VALUE": "handleLoadInitialValue"
+  },
+
+  initialize: function() {
+    this.activated = false;
+    this.value = null;
+  },
+
+  handleActivate: function() {
+    this.activated = true;
+    this.emit("change");
+  },
+
+  handleLoadInitialValue: function() {
+    this.value = "testing";
+    this.emit("change");
+  }
+});
+
+var actions = {
+  activate: function(callback) {
+    setTimeout(function() {
+      try {
+        this.dispatch("ACTIVATE");
+        callback();
+      } catch (ex) {
+        callback(ex);
+      }
+    }.bind(this));
+  },
+
+  loadInitialValue: function() {
+    this.dispatch("LOAD_INITIAL_VALUE");
+  }
+};
+
+describe("Batching updates", function() {
+  var React, TestUtils;
+  var flux, App, ComponentA, ComponentB;
+
+  beforeEach(function() {
+    global.window = jsdom.jsdom().createWindow("<html><body></body></html>");
+    global.document = window.document;
+    global.navigator = window.navigator;
+    React = require("react/addons");
+    TestUtils = React.addons.TestUtils;
+
+    flux = new Fluxxor.Flux({store: new Store()}, actions);
+
+    App = React.createClass({
+      mixins: [Fluxxor.FluxMixin(React), Fluxxor.StoreWatchMixin("store")],
+
+      getStateFromFlux: function() {
+        return {
+          activated: this.getFlux().store("store").activated
+        };
+      },
+
+      render: function() {
+        if (!this.state.activated) {
+          return React.createElement(ComponentA);
+        } else {
+          return React.createElement(ComponentB);
+        }
+      }
+    });
+
+    ComponentA = React.createClass({
+      mixins: [
+        Fluxxor.FluxMixin(React)
+      ],
+
+      render: function() {
+        return React.DOM.div();
+      }
+    });
+
+    ComponentB = React.createClass({
+      mixins: [
+        Fluxxor.FluxMixin(React),
+        Fluxxor.StoreWatchMixin("store")
+      ],
+
+      getStateFromFlux: function() {
+        return {
+          value: this.getFlux().store("store").value
+        };
+      },
+
+      componentWillMount: function() {
+        this.getFlux().actions.loadInitialValue();
+      },
+
+      render: function() {
+        return React.DOM.div();
+      },
+    });
+  });
+
+  afterEach(function() {
+    delete global.window;
+    delete global.document;
+    delete global.navigator;
+    for (var i in require.cache) {
+      if (require.cache.hasOwnProperty(i)) {
+        delete require.cache[i]; // ugh react why
+      }
+    }
+  });
+
+  it("doesn't batch by default", function(done) {
+    /* jshint expr:true */
+    TestUtils.renderIntoDocument(React.createElement(App, {flux: flux}));
+    flux.actions.activate(function(err) {
+      expect(err).to.match(/dispatch.*another action/);
+      done();
+    });
+  });
+
+  it("allows batching", function(done) {
+    /* jshint expr:true */
+    flux.setBatchingFunction(React.addons.batchedUpdates);
+
+    TestUtils.renderIntoDocument(React.createElement(App, {flux: flux}));
+    flux.actions.activate(function(err) {
+      expect(err).to.be.undefined;
+      done();
+    });
+  });
+});