问题
This is more of a "whats your opinion/Am I correct in thinking this?" question.
Trying to be as strict as possible while understanding Flux, I was trying to figure out where XHR calls are made, websockets/external stimuli handled, routing takes places, etc.
From what I read across articles, interviews and looking through facebook examples there are a few ways of handling these things. Following flux strictly, Action creators are the ones that do all the XHR calls with the possibility of a PENDING/SUCCESS/FAILURE Actions being fired before and after the request completes.
Another was, coming from facebook's Ian Obermiller, all the READ(GETs) requests are handled directly by the Stores(without involvement of an Action creator/dispatcher) and WRITE(POSTs) requests are handled by the Action Creators going through the entire action>dispatcher>store flow.
Some understandings/conclusions we drew/would like to stick to:
- Ideally, anything going in/out of the system happens only through Actions.
- Async calls leaving/entering the system will have
PENDING/PROGRESS(think file uploads)/SUCCESS/FAILUREActions. - Single dispatcher across the entire App.
Action>Dispatcher>Storecalls are strictly synchronous to stick to the dispatches not being able to start another dispatch internally to avoid chaining events/actions.- Stores are persisted across Views(considering its a single page app, you want to be able to reuse data)
A few questions that we came to some conclusion with, but I'm not entirely satisfied with:
If you take the approach where Stores do Reads, and Actions to Writes, how do you handle situations where multiple Stores might be able to use data from a single XHR call?
Example: API calls issued by TeamStore to/api/teams/{id}which returns something like:{ entities: { teams: [{ name: ..., description: ..., members: [1, 2, 4], version: ... }], users: [{ id: 1 name: ..., role: ..., version: ... }, { id: 2 name: ..., role: ..., version: ... }, { id: 3 name: ..., role: ..., version: ... }] } }Ideally, I'd also like to update the MemberStore with the information returned in this API. We maintain a version number for every entity which is updated on updates to the record, which is what we use internally do reject calls on stale data, etc. Using this, I could have an internal logic, where if I as a side effect of some other API call, I know my data is stale, I trigger a refresh on that record.
The solution, it would seem, is that you'd need the store to trigger an action(which would effectively update the other dependent stores). This short circuits the Store>View>Action to Store>Action and I'm not sure if its a good idea. We already have one thing out of sync with Stores doing their own XHR calls. Concessions like these would start creeping into the entire system eventually.
Or Stores that are aware of other stores and be able to communicate with them. But this breaks the Stores have no Setters rule.A simple solution to the above problem would be that you stick to Actions being the ONLY place external incoming/outgoing stimulus happens. This simplifies the logic of multiple Stores getting updated.
But now, where and how do you handle caching? We came to the conclusion that the caching would happen at the API Utils/DAO level. (if you look at the flux diagram).
But this introduces other problems. To better understand/explain what I mean by example:/api/teamsreturns a list of all the teams with which I display a list of all the teams.On clicking on a team's link, I go its details view which requires data from
/api/teams/{id}if it isn't already present in the Store.
If Actions handle all the XHRs, the View would do something likeTeamActions.get([id])which doesTeamDAO.get([id]). To be able to return this call immediately(since we have it cached) the DAO would have to do caching but also maintain the relation between collections/items. This logic, by design, is already present in Stores.
Here come the questions:Do you duplicate this logic in DAOs and Stores?
- Do you make DAO's aware of Stores and they can ask the Store if they already have some data and just return a 302 saying, you're good you have the latest data.
How do you handle validation that involves XHR APIs? Something simple like duplicate Team names.
Views directly hit DAOs and do something likeTeamDAO.validateName([name])which returns a promise or do you do you create an Action? If you create an Action through which Store does Valid/Invalid flow back to the View considering its mostly transient data?How do you handle Routing? I looked through react-router and I'm not sure I like it. I don't necessarily think forcing a react-ish JSX way of providing route mappings/configs are needed at all. Also, apparently, it employs a RouteDispatcher of its own, which ondoes the single dispatcher rule.
The solution I prefer came from some blog posts/SO answers where you have a the route mappings are stored in the RouteStore.
RouteStore also maintains CURRENT_VIEW. The react AppContainer component is registered with RouteStore and replaces its child views with the CURRENT_VIEW on change. Current Views inform the AppContainer when they're fully loaded and AppContainer fires RouteActions.pending/success/failure, possibly with some context, to inform other components of reaching a stable state, show/hide busy/loading indications.
Something that I have not been able to design cleanly was if you were to design routing similar to Gmail, how would you do it? Some observations of Gmail that I'm a big fan of:
- URLs don't change until the page is ready to load. It stays on the current URL while its 'Loading' and moves to the new one once the loading has finished. This makes it so that...
- On failure, you don't lose you current page at all. So if you're on compose, and the 'Send' fails, you don't lose your mail (i.e. you don't lose your current stable view/state). (they don't do this because auto saving is le pwn, but you get the idea) You have the option of copy/pasting the mail somewhere for safe keeping till you can send again.
Some references:
https://github.com/gaearon/flux-react-router-example http://ianobermiller.com/blog/2014/09/15/react-and-flux-interview/ https://github.com/facebook/flux
回答1:
It's my implementation using facebook Flux and Immutable.js that I think responds to many of your concerns, based on few rules of thumb :
STORES
- Stores are responsible for maintaining data state through Immutable.Record and maintaining cache through a global Immutable.OrderedMap referencing
Recordinstance viaids. - Stores directly call
WebAPIUtilsfor read operations and triggeractionsfor write operations. - Relationship between
RecordAandFooRecordBare resolved from aRecordAinstance through afoo_idparams and retrieved via a call such asFooStore.get(this.foo_id) - Stores only expose
gettersmethods such asget(id),getAll(), etc.
APIUTILS
- I use SuperAgent for ajax calls. Each request is wrapped in
Promise - I use a map of read request
Promiseindexed by the hash of url + params - I trigger action through ActionCreators such as fooReceived or fooError when
Promiseis resolved or rejected. fooErroraction should certainly contains payloads with validation errors returned by the server.
COMPONENTS
- The controller-view component listen for changes in store(s).
- All my components, other than controller-view component, are 'pure', so I use ImmutableRenderMixin to only re-render what it's really needed (meaning that if you print
Perf.printWastedtime, it should be very low, few ms. - Since Relay and GraphQL are not yet open sourced, I enforce to keep my component
propsas explicit as possible viapropsType. - Parent component should only passes down the necessary props. If my parent component holds an object such as
var fooRecord = { foo:1, bar: 2, baz: 3};(I'm not usingImmutable.Recordhere for the sake of simplicity of this example) and my child component need to displayfooRecord.fooandfooRecord.bar, I do not pass the entirefooobject but onlyfooRecordFooandfooRecordBaras props to my child component because an other component could edit thefoo.bazvalue, making the child component re-render while this component doesn't need at all this value !
ROUTING - I simply use ReactRouter
IMPLEMENTATION
Here is a basic example :
api
apiUtils/Request.js
var request = require('superagent');
//based on http://stackoverflow.com/a/7616484/1836434
var hashUrl = function(url, params) {
var string = url + JSON.stringify(params);
var hash = 0, i, chr, len;
if (string.length == 0) return hash;
for (i = 0, len = string.length; i < len; i++) {
chr = string.charCodeAt(i);
hash = ((hash << 5) - hash) + chr;
hash |= 0; // Convert to 32bit integer
}
return hash;
}
var _promises = {};
module.exports = {
get: function(url, params) {
var params = params || {};
var hash = hashUrl(url, params);
var promise = _promises[hash];
if (promise == undefined) {
promise = new Promise(function(resolve, reject) {
request.get(url).query(params).end( function(err, res) {
if (err) {
reject(err);
} else {
resolve(res);
}
});
});
_promises[hash] = promise;
}
return promise;
},
post: function(url, data) {
return new Promise(function(resolve, reject) {
var req = request
.post(url)
.send(data)
.end( function(err, res) {
if (err) {
reject(err);
} else {
resolve(res);
}
});
});
}
};
apiUtils/FooAPI.js
var Request = require('./Request');
var FooActionCreators = require('../actions/FooActionCreators');
var _endpoint = 'http://localhost:8888/api/foos/';
module.exports = {
getAll: function() {
FooActionCreators.receiveAllPending();
Request.get(_endpoint).then( function(res) {
FooActionCreators.receiveAllSuccess(res.body);
}).catch( function(err) {
FooActionCreators.receiveAllError(err);
});
},
get: function(id) {
FooActionCreators.receivePending();
Request.get(_endpoint + id+'/').then( function(res) {
FooActionCreators.receiveSuccess(res.body);
}).catch( function(err) {
FooActionCreators.receiveError(err);
});
},
post: function(fooData) {
FooActionCreators.savePending();
Request.post(_endpoint, fooData).then (function(res) {
if (res.badRequest) { //i.e response return code 400 due to validation errors for example
FooActionCreators.saveInvalidated(res.body);
}
FooActionCreators.saved(res.body);
}).catch( function(err) { //server errors
FooActionCreators.savedError(err);
});
}
//others foos relative endpoints helper methods...
};
stores
stores/BarStore.js
var assign = require('object-assign');
var EventEmitter = require('events').EventEmitter;
var Immutable = require('immutable');
var AppDispatcher = require('../dispatcher/AppDispatcher');
var ActionTypes = require('../constants/BarConstants').ActionTypes;
var BarAPI = require('../APIUtils/BarAPI')
var CHANGE_EVENT = 'change';
var _bars = Immutable.OrderedMap();
class Bar extends Immutable.Record({
'id': undefined,
'name': undefined,
'description': undefined,
}) {
isReady() {
return this.id != undefined //usefull to know if we can display a spinner when the Bar is loading or the Bar's data if it is ready.
}
getBar() {
return BarStore.get(this.bar_id);
}
}
function _rehydrate(barId, field, value) {
//Since _bars is an Immutable, we need to return the new Immutable map. Immutable.js is smart, if we update with the save values, the same reference is returned.
_bars = _bars.updateIn([barId, field], function() {
return value;
});
}
var BarStore = assign({}, EventEmitter.prototype, {
get: function(id) {
if (!_bars.has(id)) {
BarAPI.get(id);
return new Bar(); //we return an empty Bar record for consistency
}
return _bars.get(id)
},
getAll: function() {
return _bars.toList() //we want to get rid of keys and just keep the values
},
Bar: Bar,
emitChange: function() {
this.emit(CHANGE_EVENT);
},
addChangeListener: function(callback) {
this.on(CHANGE_EVENT, callback);
},
removeChangeListener: function(callback) {
this.removeListener(CHANGE_EVENT, callback);
},
});
var _setBar = function(barData) {
_bars = _bars.set(barData.id, new Bar(barData));
};
var _setBars = function(barList) {
barList.forEach(function (barData) {
_setbar(barData);
});
};
BarStore.dispatchToken = AppDispatcher.register(function(action) {
switch (action.type)
{
case ActionTypes.BAR_LIST_RECEIVED_SUCESS:
_setBars(action.barList);
BarStore.emitChange();
break;
case ActionTypes.BAR_RECEIVED_SUCCESS:
_setBar(action.bar);
BarStore.emitChange();
break;
case ActionTypes.BAR_REHYDRATED:
_rehydrate(
action.barId,
action.field,
action.value
);
BarStore.emitChange();
break;
}
});
module.exports = BarStore;
stores/FooStore.js
var assign = require('object-assign');
var EventEmitter = require('events').EventEmitter;
var Immutable = require('immutable');
var AppDispatcher = require('../dispatcher/AppDispatcher');
var ActionTypes = require('../constants/FooConstants').ActionTypes;
var BarStore = require('./BarStore');
var FooAPI = require('../APIUtils/FooAPI')
var CHANGE_EVENT = 'change';
var _foos = Immutable.OrderedMap();
class Foo extends Immutable.Record({
'id': undefined,
'bar_id': undefined, //relation to Bar record
'baz': undefined,
}) {
isReady() {
return this.id != undefined;
}
getBar() {
// The whole point to store an id reference to Bar
// is to delegate the Bar retrieval to the BarStore,
// if the BarStore does not have this Bar object in
// its cache, the BarStore will trigger a GET request
return BarStore.get(this.bar_id);
}
}
function _rehydrate(fooId, field, value) {
_foos = _foos.updateIn([voucherId, field], function() {
return value;
});
}
var _setFoo = function(fooData) {
_foos = _foos.set(fooData.id, new Foo(fooData));
};
var _setFoos = function(fooList) {
fooList.forEach(function (foo) {
_setFoo(foo);
});
};
var FooStore = assign({}, EventEmitter.prototype, {
get: function(id) {
if (!_foos.has(id)) {
FooAPI.get(id);
return new Foo();
}
return _foos.get(id)
},
getAll: function() {
if (_foos.size == 0) {
FooAPI.getAll();
}
return _foos.toList()
},
Foo: Foo,
emitChange: function() {
this.emit(CHANGE_EVENT);
},
addChangeListener: function(callback) {
this.on(CHANGE_EVENT, callback);
},
removeChangeListener: function(callback) {
this.removeListener(CHANGE_EVENT, callback);
},
});
FooStore.dispatchToken = AppDispatcher.register(function(action) {
switch (action.type)
{
case ActionTypes.FOO_LIST_RECEIVED_SUCCESS:
_setFoos(action.fooList);
FooStore.emitChange();
break;
case ActionTypes.FOO_RECEIVED_SUCCESS:
_setFoo(action.foo);
FooStore.emitChange();
break;
case ActionTypes.FOO_REHYDRATED:
_rehydrate(
action.fooId,
action.field,
action.value
);
FooStore.emitChange();
break;
}
});
module.exports = FooStore;
components
components/BarList.react.js (controller-view component)
var React = require('react/addons');
var Immutable = require('immutable');
var BarListItem = require('./BarListItem.react');
var BarStore = require('../stores/BarStore');
function getStateFromStore() {
return {
barList: BarStore.getAll(),
};
}
module.exports = React.createClass({
getInitialState: function() {
return getStateFromStore();
},
componentDidMount: function() {
BarStore.addChangeListener(this._onChange);
},
componentWillUnmount: function() {
BarStore.removeChangeListener(this._onChange);
},
render: function() {
var barItems = this.state.barList.toJS().map(function (bar) {
// We could pass the entire Bar object here
// but I tend to keep the component not tightly coupled
// with store data, the BarItem can be seen as a standalone
// component that only need specific data
return <BarItem
key={bar.get('id')}
id={bar.get('id')}
name={bar.get('name')}
description={bar.get('description')}/>
});
if (barItems.length == 0) {
return (
<p>Loading...</p>
)
}
return (
<div>
{barItems}
</div>
)
},
_onChange: function() {
this.setState(getStateFromStore();
}
});
components/BarListItem.react.js
var React = require('react/addons');
var ImmutableRenderMixin = require('react-immutable-render-mixin')
var Immutable = require('immutable');
module.exports = React.createClass({
mixins: [ImmutableRenderMixin],
// I use propTypes to explicitly telling
// what data this component need. This
// component is a standalone component
// and we could have passed an entire
// object such as {id: ..., name, ..., description, ...}
// since we use all the datas (and when we use all the data it's
// a better approach since we don't want to write dozens of propTypes)
// but let's do that for the example's sake
propTypes: {
id: React.PropTypes.number.isRequired,
name: React.PropTypes.string.isRequired,
description: React.PropTypes.string.isRequired
}
render: function() {
return (
<li>
<p>{this.props.id}</p>
<p>{this.props.name}</p>
<p>{this.props.description}</p>
</li>
)
}
});
components/BarDetail.react.js
var React = require('react/addons');
var ImmutableRenderMixin = require('react-immutable-render-mixin')
var Immutable = require('immutable');
var BarActionCreators = require('../actions/BarActionCreators');
module.exports = React.createClass({
mixins: [ImmutableRenderMixin],
propTypes: {
id: React.PropTypes.number.isRequired,
name: React.PropTypes.string.isRequired,
description: React.PropTypes.string.isRequired
},
handleSubmit: function(event) {
//Since we keep the Bar data up to date with user input
//we can simply save the actual object in Store.
//If the user goes back without saving, we could display a
//"Warning : item not saved"
BarActionCreators.save(this.props.id);
},
handleChange: function(event) {
BarActionCreators.rehydrate(
this.props.id,
event.target.name, //the field we want to rehydrate
event.target.value //the updated value
);
},
render: function() {
return (
<form onSubmit={this.handleSumit}>
<input
type="text"
name="name"
value={this.props.name}
onChange={this.handleChange}/>
<textarea
name="description"
value={this.props.description}
onChange={this.handleChange}/>
<input
type="submit"
defaultValue="Submit"/>
</form>
)
},
});
components/FooList.react.js (controller-view component)
var React = require('react/addons');
var FooStore = require('../stores/FooStore');
var BarStore = require('../stores/BarStore');
function getStateFromStore() {
return {
fooList: FooStore.getAll(),
};
}
module.exports = React.createClass({
getInitialState: function() {
return getStateFromStore();
},
componentDidMount: function() {
FooStore.addChangeListener(this._onChange);
BarStore.addChangeListener(this._onChange);
},
componentWillUnmount: function() {
FooStore.removeChangeListener(this._onChange);
BarStore.removeChangeListener(this._onChange);
},
render: function() {
if (this.state.fooList.size == 0) {
return <p>Loading...</p>
}
return this.state.fooList.toJS().map(function (foo) {
<FooListItem
fooId={foo.get('id')}
fooBar={foo.getBar()}
fooBaz={foo.get('baz')}/>
});
},
_onChange: function() {
this.setState(getStateFromStore();
}
});
components/FooListItem.react.js
var React = require('react/addons');
var ImmutableRenderMixin = require('react-immutable-render-mixin')
var Bar = require('../stores/BarStore').Bar;
module.exports = React.createClass({
mixins: [ImmutableRenderMixin],
propTypes: {
fooId: React.PropTypes.number.isRequired,
fooBar: React.PropTypes.instanceOf(Bar).isRequired,
fooBaz: React.PropTypes.string.isRequired
}
render: function() {
//we could (should) use a component here but this answer is already too long...
var bar = <p>Loading...</p>;
if (bar.isReady()) {
bar = (
<div>
<p>{bar.get('name')}</p>
<p>{bar.get('description')}</p>
</div>
);
}
return (
<div>
<p>{this.props.fooId}</p>
<p>{this.props.fooBaz}</p>
{bar}
</div>
)
},
});
Let's go through an entire loop for FooList:
State 1:
- User hits the page /foos/ listing the Foos via the
FooListcontroller-view component FooListcontroller-view component callsFooStore.getAll()_foosmap is empty inFooStoresoFooStoreperforms a request viaFooAPI.getAll()- The
FooListcontroller-view component renders itself as loading state since itsstate.fooList.size == 0.
Here's the actual look of our list :
++++++++++++++++++++++++
+ +
+ "loading..." +
+ +
++++++++++++++++++++++++
FooAPI.getAll()request resolves and triggers theFooActionCreators.receiveAllSuccessactionFooStorereceive this action, updates its internal state, and emits change.
State 2:
FooListcontroller-view component receive change event and update its state to get the list from theFooStorethis.state.fooList.sizeis no longer== 0so the list can actually renders itself (note that we usetoJS()to explicitly get a raw javascript object sinceReactdoes not handle correctly mapping on not raw object yet).- We're passing needed props to the
FooListItemcomponent. - By calling
foo.getBar()we're telling to theFooStorethat we want theBarrecord back. getBar()method ofFoorecord retrieve theBarrecord through theBarStoreBarStoredoes not have thisBarrecord in its_barscache, so it triggers a request throughBarAPIto retrieve it.- The same happens for all
Foointhis.sate.fooListofFooListcontroller-view component - The page now looks something like this:
++++++++++++++++++++++++ + + + Foo1 "name1" + + Foo1 "baz1" + + Foo1 bar: + + "loading..." + + + + Foo2 "name2" + + Foo2 "baz2" + + Foo2 bar: + + "loading..." + + + + Foo3 "name3" + + Foo3 "baz3" + + Foo3 bar: + + "loading..." + + + ++++++++++++++++++++++++
-Now let's say the BarAPI.get(2) (requested by Foo2) resolves before BarAPI.get(1) (request by Foo1). Since it's asynchronous it's totally plausible.
- The BarAPI triggers the BAR_RECEIVED_SUCCESS' action via theBarActionCreators.
- TheBarStore` responds to this action by updating its internal store and emits change. That's the now the fun part...
State 3:
- The
FooListcontroller-view component responds to theBarStorechange by updating its state. - The
rendermethod is called - The
foo.getBar()call now retrieve a realBarrecord fromBarStore. Since thisBarrecord has been effectively retrieved, theImmutablePureRenderMixinwill compare old props with current props and determine that theBarobjects has changed ! Bingo, we could re-render theFooListItemcomponent (a better approach here would be to create a separate FooListBarDetail component to let only this component to re-render, here we also re-rendering the Foo's details that have not changed but for the sake of simplicity let's just do that). - The page now looks like this :
++++++++++++++++++++++++ + + + Foo1 "name1" + + Foo1 "baz1" + + Foo1 bar: + + "loading..." + + + + Foo2 "name2" + + Foo2 "baz2" + + Foo2 bar: + + "bar name" + + "bar description" + + + + Foo3 "name3" + + Foo3 "baz3" + + Foo3 bar: + + "loading..." + + + ++++++++++++++++++++++++
If you want me to add more details from a non detailed part (such as action creators, constants, routing, etc., use of BarListDetail component with form, POST, etc.) just tell me in the comments :).
回答2:
A few differences in my implementation:
I like stores employing a flyweight pattern. That is, unless forced to, all operations are "getOrRetrieveOrCreate"
I've had to forgo promise heavy development in favor of events/state. Async communication should still use promises, that is, things in actions use them otherwise communication occurs using events. If a view always renders the current state, then you need a state like "isLoading" to render a spinner. Or you need an event to get fired then update a state on a view. I think responding from an action with a promise may be an anti-pattern (not entirely sure).
URL changes fire the appropriate action. GET should work and be idempotent so a URL change should generally not result in a failure. It may however result in a redirect. I have an "authRequired" decorator for some actions. If you aren't authenticated then we redirect you to the login page with the target URL listed as a redirect path.
For validation we are thinking about starting from an action, firing a "xyzModel:willSaveData", before we start; then firing either "xyzModel:didSaveData" or "xyzModel:failedSaveData" events. The store listening to these events will indicate "saving" to the views that care. It may also indicate "hasValidationError" to views that care. If you want to dismiss an error. You can fire an action from a view that indicates that the error "wasReceived", which removes the "hasValidationError" flag or optionally could do something else like clear out all validation errors. Validations are interesting because of the different styles of validation. Ideally, you could create an app that would accept most any input due the limitations imposed by your input elements. Then again, servers may disagree with those choices :/.
来源：https://stackoverflow.com/questions/28060493/react-flux-and-xhr-routing-caching