FishRedux中的Dispatch如何实现-创新互联
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创新互联专业提供成都主机托管四川主机托管成都服务器托管四川服务器托管,支持按月付款!我们的承诺:贵族品质、平民价格,机房位于中国电信/网通/移动机房,四川电信科技城机房服务有保障!前言我们在使用fish-redux构建应用的时候,界面代码(view)和事件的处理逻辑(reducer,effect)是完全解耦的,界面需要处理事件的时候将action分发给对应的事件处理逻辑去进行处理,而这个分发的过程就是下面要讲的dispatch, 通过本篇的内容,你可以更深刻的理解一个action是如何一步步去进行分发的。
从example开始为了更好的理解action的dispatch过程,我们就先以todolistpage中一条todo条目的勾选事件为例,来看点击后事件的传递过程,通过断点debug我们很容易就能够发现点击时候发生的一切,具体过程如下:
用户点击勾选框,GestureDetector的onTap会被回调
通过buildView传入的dispatch函数对doneAction进行分发,发现todo_component的effect中无法处理此doneAction,所以将其交给pageStore的dispatch继续进行分发
pageStore的dispatch会将action交给reducer进行处理,故doneAction对应的_markDone会被执行,对state进行clone,并修改clone后的state的状态,然后将这个全新的state返回
然后pageStore的dispatch会通知所有的listeners,其中负责界面重绘的_viewUpdater发现state发生变化,通知界面进行重绘更新
Dispatch在fish-redux中的定义如下
typedef Dispatch = void Function(Action action);
本质上就是一个action的处理函数,接受一个action,然后对action进行分发。
下面我门通过源码来进行详细的分析。
0component->ComponentWidget->ComponentState->_mainCtx->_dispatch而 _mainCtx的初始化则是通过componet的createContext方法来创建的,顺着方法下去我们看到了dispatch的初始化
// redux_component/context.dart DefaultContext初始化方法
DefaultContext({
@required this.factors,
@required this.store,
@required BuildContext buildContext,
@required this.getState,
}) : assert(factors != null),
assert(store != null),
assert(buildContext != null),
assert(getState != null),
_buildContext = buildContext {
final OnAction onAction = factors.createHandlerOnAction(this);
/// create Dispatch
_dispatch = factors.createDispatch(onAction, this, store.dispatch);
/// Register inter-component broadcast
_onBroadcast =
factors.createHandlerOnBroadcast(onAction, this, store.dispatch);
registerOnDisposed(store.registerReceiver(_onBroadcast));
}
context中的dispatch是通过factors来进行创建的,factors其实就是当前component,factors创建dispatch的时候传入了onAction函数,以及context自己和store的dispatch。onAction主要是进行Effect处理。这边还可以看到,进行context初始化的最后,还将自己的onAction包装注册到store的广播中去,这样就可以接收到别人发出的action广播。
Component继承自Logic
// redux_component/logic.dart
@override
Dispatch createDispatch(
OnAction onAction, Context
ctx, Dispatch parentDispatch) {
Dispatch dispatch = (Action action) {
throw Exception(
'Dispatching while appending your effect & onError to dispatch is not allowed.');
};
/// attach to store.dispatch
dispatch = _applyOnAction
(onAction, ctx)(
dispatch: (Action action) => dispatch(action),
getState: () => ctx.state,
)(parentDispatch);
return dispatch;
}
static Middleware
_applyOnAction (OnAction onAction, Context ctx) {
return ({Dispatch dispatch, Get
getState}) {
return (Dispatch next) {
return (Action action) {
final Object result = onAction?.call(action);
if (result != null && result != false) {
return;
}
//skip-lifecycle-actions
if (action.type is Lifecycle) {
return;
}
if (!shouldBeInterruptedBeforeReducer(action)) {
ctx.pageBroadcast(action);
}
next(action);
};
};
};
}
}
上面分发的逻辑大概可以通过上图来表示
通过onAction将action交给component对应的effect进行处理
当effect无法处理此action,且此action非lifecycle-actions,且不需中断则广播给当前Page的其余所有effects
最后就是继续将action分发给store的dispatch(parentDispatch传入的其实就是store.dispatch)
0
// redux/create_store.dart
final Dispatch dispatch = (Action action) {
_throwIfNot(action != null, 'Expected the action to be non-null value.');
_throwIfNot(
action.type != null, 'Expected the action.type to be non-null value.');
_throwIfNot(!isDispatching, 'Reducers may not dispatch actions.');
try {
isDispatching = true;
state = reducer(state, action);
} finally {
isDispatching = false;
}
final List<_VoidCallback> _notifyListeners = listeners.toList(
growable: false,
);
for (_VoidCallback listener in _notifyListeners) {
listener();
}
notifyController.add(state);
};
// redux_component/component.dart
Widget buildPage(P param) {
return wrapper(_PageWidget
( component: this,
storeBuilder: () => createPageStore
( initState(param),
reducer,
applyMiddleware
(buildMiddleware(middleware)), ),
));
}
// redux_component/page_store.dart
PageStore
createPageStore (T preloadedState, Reducer reducer, [StoreEnhancer
enhancer]) => _PageStore
(createStore(preloadedState, reducer, enhancer)); // redux/create_store.dart
Store
createStore (T preloadedState, Reducer reducer, [StoreEnhancer
enhancer]) => enhancer != null
? enhancer(_createStore)(preloadedState, reducer)
: _createStore(preloadedState, reducer);
store的dispatch过程比较简单,主要就是进行reducer的调用,处理完成后通知监听者。
0
所以这里可以看到,当传入enhancer时,createStore的工作被enhancer代理了,会返回一个经过enhancer处理过的store。而PageStore创建的时候传入的是中间件的enhancer。
// redux/apply_middleware.dart
StoreEnhancer
applyMiddleware (List > middleware) {
return middleware == null || middleware.isEmpty
? null
: (StoreCreator
creator) => (T initState, Reducer reducer) {
assert(middleware != null && middleware.isNotEmpty);
final Store
store = creator(initState, reducer);
final Dispatch initialValue = store.dispatch;
store.dispatch = (Action action) {
throw Exception(
'Dispatching while constructing your middleware is not allowed. '
'Other middleware would not be applied to this dispatch.');
};
store.dispatch = middleware
.map((Middleware
middleware) => middleware(
dispatch: (Action action) => store.dispatch(action),
getState: store.getState,
))
.fold(
initialValue,
(Dispatch previousValue,
Dispatch Function(Dispatch) element) =>
element(previousValue),
);
return store;
};
}
这里的逻辑其实就是将所有的middleware的处理函数都串到store的dispatch,这样当store进行dispatch的时候所有的中间件的处理函数也会被调用。下面为各个处理函数的执行顺序,
首先还是component中的dispatch D1 会被执行,然后传递给store的dispatch,而此时store的dispatch已经经过中间件的增强,所以会执行中间件的处理函数,最终store的原始dispatch函数D2会被执行。
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