[Getx]记Get.find()依赖绑错路由问题(二):get:5.0.0-beta.52在复杂场景下GetLifeC

对getx 源码的改造及原因

为什么要改造源码
- 在复杂场景下logic 会绑错路由的情况
- 上面的链接是Getx 4.6.1的改造,这次针对 get: 5.0.0-beta.52 修改,主要针对与5.0.0 推出的Bind适配

改造思路

首先要理解作者推出Bind的思路,这次5.0.0升级废弃了Bindings

/// [Bindings] should be extended or implemented.
/// When using `GetMaterialApp`, all `GetPage`s and navigation
/// methods (like Get.to()) have a `binding` property that takes an
/// instance of Bindings to manage the
/// dependencies() (via Get.put()) for the Route you are opening.
// ignore: one_member_abstracts
@Deprecated('Use Binding instead')
abstract class Bindings extends BindingsInterface<void> {
  @override
  void dependencies();
}

然后推出Binding

/// [Binding] should be extended.
/// When using `GetMaterialApp`, all `GetPage`s and navigation
/// methods (like Get.to()) have a `binding` property that takes an
/// instance of Bindings to manage the
/// dependencies() (via Get.put()) for the Route you are opening.
// ignore: one_member_abstracts
abstract class Binding extends BindingsInterface<List<Bind>> {}

区别在dependencies() 返回值,现在为List<Bind>, 我们知道这个dependencies()方法作用是给GetPage注入依赖,在推入GetPage入栈时BuildWidget调用

 // get 4.6.1
 ...
 final localbindings = [
   if (bindings != null) ...bindings!,
   if (binding != null) ...[binding!]
 ];
 final bindingsToBind = middlewareRunner.runOnBindingsStart(localbindings);
 if (bindingsToBind != null) {
   for (final binding in bindingsToBind) {
     binding.dependencies();
   }
 }

 final pageToBuild = middlewareRunner.runOnPageBuildStart(page)!;
 _child = middlewareRunner.runOnPageBuilt(pageToBuild());
 return _child!;
 ...

//get 5.0.0
final localbinds = [if (binds != null) ...binds!];

 final bindingsToBind = middlewareRunner
     .runOnBindingsStart(bindings.isNotEmpty ? bindings : localbinds);

 final pageToBuild = middlewareRunner.runOnPageBuildStart(page)!;

 if (bindingsToBind != null && bindingsToBind.isNotEmpty) {
   if (bindingsToBind is List<BindingsInterface>) {
     for (final item in bindingsToBind) {
       final dep = item.dependencies();
       //为了兼容4.x.x,如果返回List<Bind> 则使用Binds 包裹
       if (dep is List<Bind>) {
         _child = Binds(
           child: middlewareRunner.runOnPageBuilt(pageToBuild()),
           binds: dep,
         );
       }
       // 如果返回void,则是4.x.x版本
     }
   } else if (bindingsToBind is List<Bind>) {
     //处理直接GetPage直接传参binds时情况
     _child = Binds(
       child: middlewareRunner.runOnPageBuilt(pageToBuild()),
       binds: bindingsToBind,
     );
   }
 }

 return _child ??= middlewareRunner.runOnPageBuilt(pageToBuild());

那么这里出现的Binds做了什么处理呢

class Binds extends StatelessWidget {
 //简单的无状态Widget
 final List<Bind<dynamic>> binds;
 final Widget child;

 Binds({
   Key? key,
   required this.binds,
   required this.child,
 })
     : assert(binds.isNotEmpty),
       super(key: key);

  @override
 Widget build(BuildContext context) =>
 //将binds倒序迭代包裹本身,并生成一个Widget并返回
     binds.reversed.fold(child, (widget, e) => e._copyWithChild(widget));
}

接下来看Bind又是啥,_copyWithChild(widget)又做了什么处理

//本身是一个抽象类,提供_copyWithChild()接口,且本身是无状态Widget,所以可以在Binds.build()迭代并返回
abstract class Bind<T> extends StatelessWidget {
 ...

 @factory
 Bind<T> _copyWithChild(Widget child);

 //提供一个builder直接调用私有实现
 factory Bind.builder({
     ...
   }) =>
   _FactoryBind<T>(
     ...
   );
}
//实现类
class _FactoryBind<T> extends Bind<T> {

 @override
 Bind<T> _copyWithChild(Widget child) {
   return Bind<T>.builder(
     ...
 );
}

@override
 Widget build(BuildContext context) {
   //最终返回一个Binder,具体实现都在Binder中
   return Binder<T>(
   ...
   child: child!,
   );
  }
 }

重点来了,前面都的处理都是提供接口以及迭代包括,那么处理逻辑都存在Binder中

//继承InheritedWidget,可通过上下文做数据共享
class Binder<T> extends InheritedWidget {
 /// Create an inherited widget that updates its dependents when [controller]
 /// sends notifications.
 ///
 /// The [child] argument is required
 const Binder({
   ...
 }) : super(key: key, child: child);

 ...

 @override
 bool updateShouldNotify(Binder<T> oldWidget) {
   return oldWidget.id != id ||
       oldWidget.global != global ||
       oldWidget.autoRemove != autoRemove ||
       oldWidget.assignId != assignId;
 }

 @override
 InheritedElement createElement() => BindElement<T>(this);
 }
 //具体逻辑操作在element体现,具体源码见 https://github.com/jonataslaw/getx/blob/master/lib/get_state_manager/src/simple/get_state.dart
 //这里只关注 initState 与 dispose
 class BindElement<T> extends InheritedElement {
 BindElement(Binder<T> widget) : super(widget) {
   //在element初始化时调用initState(); tips: widget挂载时(Element inflateWidget(Widget newWidget, Object? newSlot))调用XXElement.createElement();
   initState();
 }

 ...


 void initState() {
   widget.initState?.call(this);

   var isRegistered = Get.isRegistered<T>(tag: widget.tag);

   //是否注册到全局单例
   if (widget.global) {
     if (isRegistered) {
       //已经注册,重置
       if (Get.isPrepared<T>(tag: widget.tag)) {
         _isCreator = true;
       } else {
         _isCreator = false;
       }

       _controllerBuilder = () => Get.find<T>(tag: widget.tag);
     } else {
       _controllerBuilder =
           () => (widget.create?.call(this) ?? widget.init?.call());
       _isCreator = true;
       //注册到全局单例池,等同于4.x.x 之前在void dependencies(){
         //Get.lazyPut<T>(_controllerBuilder!, tag: widget.tag);
         //or
         //Get.put<T>(_controllerBuilder!(), tag: widget.tag);
       //}
       if (widget.lazy) {
         Get.lazyPut<T>(_controllerBuilder!, tag: widget.tag);
       } else {
         Get.put<T>(_controllerBuilder!(), tag: widget.tag);
       }
     }
   } else {
     _controllerBuilder =
         (widget.create != null ? () => widget.create!.call(this) : null) ??
             widget.init;
     _isCreator = true;
     _needStart = true;
   }
 }

 ...

 void dispose() {
   widget.dispose?.call(this);
   if (_isCreator! || widget.assignId) {
     //可以通过autoRemove 由自身控制其生命周期
     if (widget.autoRemove && Get.isRegistered<T>(tag: widget.tag)) {
       Get.delete<T>(tag: widget.tag);
     }
   }

   ...
 }

 ...

 @override
 void unmount() {
   //卸载时调用dispose()
   dispose();
   super.unmount();
 }
}

通过翻阅源码,我大胆猜测作者使用Bind目的是拓展GetPage.bindings的功能,将组件put依赖的能力封装到Bind中,并拓展其自动管理生命周期的能力,4.x.x版本组件的依赖跟组件本身并不是强关联,Bingings里面不能很好的控制其生命周期,生命周期的控制是通过RouterReportManager加上Get.find()维护一个Map<routeName,List>,通过监听GetRoute路由的动作来控制depedency的销毁

开始改造

为啥还需要改造呢?复杂业务情况下,我们希望组件依赖的生命周期不能跟随组件的生命周期,而是类似与之前文章的根据路由的操作而定而在复杂场景下logic 会绑错路由的情况这个问题依旧存在,不同的是,现在可以在put() or lazyPut() 拿到当前context,继而拿到当前路由,但是我们知道,RouterReportManager绑定depedencyKey是在Get.find(),所以4.x.x的改造思路是在find时加上context绑定到正确的路由上,那么现在的做法需要怎么做呢,首先我们假定RouterReportManager中currentRoute不可信,问题见. 可信的routeName从哪里获取,Bind .put() or .lazyPut() 时一定是对的,所以需要在RouterReportManager中维护一个Map<BindRoute,epedencyKey>来维系对应路由

  class RouterReportManager<T> {
   ...
   ///保存bind 加载的depedencyKey,绑定到对应的context.route上
   final Map<String, T> _depeKey2BindRoute = {};
   ...

   ///获取可能bind的route
   T? _bindRoute(String depedencyKey) => _depeKey2BindRoute[depedencyKey]??_current;

   ///上报依赖绑定的对应的bindContext.route
   void reportDepeKey2BindRoute(String depedencyKey, T? routeName) {
     if (!_depeKey2BindRoute.containsKey(depedencyKey)) {
       if (routeName != null) {
         _depeKey2BindRoute.addAll({depedencyKey: routeName});
       }
     }
   }
   ///Get.find 时 修正绑定的route
   void reportDependencyLinkedToRoute(String depedencyKey) {
     final _bind = _bindRoute(depedencyKey);
     if (_bind == null) return;
     if (_routesKey.containsKey(_bind ?? _current)) {
       _routesKey[_bind]!.add(depedencyKey);
     } else {
       _routesKey[_bind] = <String>[depedencyKey];
     }
   }
 }

还剩一个问题,怎么调用reportDepeKey2BindRoute()上报

 static Bind lazyPut<S>(InstanceBuilderCallback<S> builder, {
   String? tag,
   bool fenix = true,
   // VoidCallback? onInit,
   VoidCallback? onClose,
   bool autoRemove = true, //tip 业务会用到,直接在源码上修改开出去使用
 }) {
   Get.lazyPut<S>(builder, tag: tag, fenix: fenix);
   return _FactoryBind<S>(
     tag: tag,
     autoRemove: autoRemove,
     initState: (_) {
       //onInit
       //不能在initState中调用context.dependOnInheritedWidgetOfExactType,所以加个帧回调
       //上报
       SchedulerBinding.instance.addPostFrameCallback((timeStamp) {
         RouterReportManager.instance
             .reportDepeKey2BindRoute(Get.getKey(S, tag), ModalRoute.of(_));
       });
     },
     dispose: (_) {
       onClose?.call();
     },
   );
 }

到此为,改造完成,业务使用,例:

 class LoginBinding extends Binding {
   @override
   List<Bind> dependencies() {
     return [
       Bind.lazyPut(() => LoginController()),
     ];
   }
 }

GetView不需要丑陋的继承context,也能在find时找到正确的context2bind

尾声
纯个人理解,难免片面或者有误,有不同的看法多多交流,谢谢

[Getx]记Get.find()依赖绑错路由问题(二):get:5.0.0-beta.52

对getx 源码的改造及原因

为什么要改造源码

改造思路

开始改造

尾声