javascript - 如何为 Angular 2 中的特定路由实现 RouteReuseStrategy shouldDetach

Question

我有一个 Angular 2 模块，我在其中实现了路由，并希望在导航时存储状态。
用户应该能够:

使用“搜索公式”搜索文档

导航到结果之一

导航回“搜索结果” - 不与服务器通信

这是可能的，包括 RouteReuseStrategy .
问题是:
如何实现不应存储文档？
所以应该存储路由路径“documents”的状态，而不应该存储路由路径“documents/:id”的状态？

Answer 1

嘿安德斯，好问题!

我有和你几乎一样的用例，并且想做同样的事情!用户搜索 > 获取结果 > 用户导航到结果 > 用户返回 > 繁荣 快速返回结果，但您不想存储用户导航到的特定结果。

tl;博士

您需要有一个实现 RouteReuseStrategy 的类并在 ngModule 中提供您的策略.如果要修改路由存储时，修改shouldDetach功能。当它返回时 true , Angular 存储路由。如果要在附加路由时修改，修改shouldAttach功能。当shouldAttach返回 true，Angular 将使用存储的路由代替请求的路由。这是一个 Plunker供你玩耍。

关于RouteReuseStrategy

通过问这个问题，您已经了解 RouteReuseStrategy 允许您告诉 Angular 不要销毁组件，而实际上是保存它以供以后重新渲染。这很酷，因为它允许:

减少服务器调用

提速

并且组件在默认情况下呈现在与它相同的状态

如果您想暂时离开页面，即使用户输入了 ，最后一个也很重要。拍品 的文本。由于表单数量过多，企业应用程序会喜欢此功能!

这就是我想出的解决问题的方法。正如你所说，你需要利用 RouteReuseStrategy由 @angular/router 在 3.4.1 及更高版本中提供。

待办事项

第一 确保您的项目具有 @angular/router 版本 3.4.1 或更高版本。

下一个 , 创建一个文件，该文件将容纳实现 RouteReuseStrategy 的类.我调用我的 reuse-strategy.ts并将其放入 /app用于保管的文件夹。现在，这个类应该是这样的:

import { RouteReuseStrategy } from '@angular/router';

export class CustomReuseStrategy implements RouteReuseStrategy {
}

(不要担心您的 TypeScript 错误，我们将解决所有问题)

完成基础工作 通过将类(class)提供给您的 app.module .请注意，您还没有写 CustomReuseStrategy ，但应该继续和 import它来自 reuse-strategy.ts都一样。还有 import { RouteReuseStrategy } from '@angular/router';

@NgModule({
    [...],
    providers: [
        {provide: RouteReuseStrategy, useClass: CustomReuseStrategy}
    ]
)}
export class AppModule {
}

最后一块 正在编写控制路由是否分离、存储、检索和重新附加的类。在我们讨论旧的复制/粘贴之前，我将在这里对机制做一个简短的解释，据我所知。对于我描述的方法，请引用下面的代码，当然还有大量文档 在代码中 .

导航时，shouldReuseRoute火灾。这个对我来说有点奇怪，但如果它返回 true ，然后它实际上会重用您当前所在的路线，并且不会触发任何其他方法。如果用户正在导航，我只会返回 false。

如 shouldReuseRoute返回 false , shouldDetach火灾。 shouldDetach确定是否要存储路由，并返回 boolean表示一样多。 这是您应该决定存储/不存储路径的地方 ，我会通过检查要存储的路径数组来实现 route.routeConfig.path , 如果 path 返回 false不存在于数组中。

如 shouldDetach返回 true , store被解雇，这是您存储您想要的有关路线的任何信息的机会。无论您做什么，您都需要存储 DetachedRouteHandle因为这是 Angular 稍后用来识别您存储的组件的内容。下面，我存储了 DetachedRouteHandle和 ActivatedRouteSnapshot进入我类(class)的本地变量。

所以，我们已经看到了存储的逻辑，但是导航到一个组件呢？ Angular 如何决定拦截你的导航并将存储的导航放在它的位置？

再次，在 shouldReuseRoute 之后已返回 false , shouldAttach运行，这是您确定是否要重新生成或使用内存中的组件的机会。如果要重用已存储的组件，请返回 true一切顺利!

现在 Angular 会问你，“你想让我们使用哪个组件？”，你将通过返回该组件的 DetachedRouteHandle 来指明这一点。来自 retrieve .

这几乎就是您需要的所有逻辑!在 reuse-strategy.ts 的代码中，下面，我还给你留下了一个漂亮的函数，可以比较两个对象。我用它来比较 future 路线的 route.params和 route.queryParams与存储的。如果这些都匹配，我想使用存储的组件而不是生成一个新的组件。但是你怎么做是 由你决定!

重用策略.ts

/**
 * reuse-strategy.ts
 * by corbfon 1/6/17
 */

import { ActivatedRouteSnapshot, RouteReuseStrategy, DetachedRouteHandle } from '@angular/router';

/** Interface for object which can store both: 
 * An ActivatedRouteSnapshot, which is useful for determining whether or not you should attach a route (see this.shouldAttach)
 * A DetachedRouteHandle, which is offered up by this.retrieve, in the case that you do want to attach the stored route
 */
interface RouteStorageObject {
    snapshot: ActivatedRouteSnapshot;
    handle: DetachedRouteHandle;
}

export class CustomReuseStrategy implements RouteReuseStrategy {

    /** 
     * Object which will store RouteStorageObjects indexed by keys
     * The keys will all be a path (as in route.routeConfig.path)
     * This allows us to see if we've got a route stored for the requested path
     */
    storedRoutes: { [key: string]: RouteStorageObject } = {};

    /** 
     * Decides when the route should be stored
     * If the route should be stored, I believe the boolean is indicating to a controller whether or not to fire this.store
     * _When_ it is called though does not particularly matter, just know that this determines whether or not we store the route
     * An idea of what to do here: check the route.routeConfig.path to see if it is a path you would like to store
     * @param route This is, at least as I understand it, the route that the user is currently on, and we would like to know if we want to store it
     * @returns boolean indicating that we want to (true) or do not want to (false) store that route
     */
    shouldDetach(route: ActivatedRouteSnapshot): boolean {
        let detach: boolean = true;
        console.log("detaching", route, "return: ", detach);
        return detach;
    }

    /**
     * Constructs object of type `RouteStorageObject` to store, and then stores it for later attachment
     * @param route This is stored for later comparison to requested routes, see `this.shouldAttach`
     * @param handle Later to be retrieved by this.retrieve, and offered up to whatever controller is using this class
     */
    store(route: ActivatedRouteSnapshot, handle: DetachedRouteHandle): void {
        let storedRoute: RouteStorageObject = {
            snapshot: route,
            handle: handle
        };

        console.log( "store:", storedRoute, "into: ", this.storedRoutes );
        // routes are stored by path - the key is the path name, and the handle is stored under it so that you can only ever have one object stored for a single path
        this.storedRoutes[route.routeConfig.path] = storedRoute;
    }

    /**
     * Determines whether or not there is a stored route and, if there is, whether or not it should be rendered in place of requested route
     * @param route The route the user requested
     * @returns boolean indicating whether or not to render the stored route
     */
    shouldAttach(route: ActivatedRouteSnapshot): boolean {

        // this will be true if the route has been stored before
        let canAttach: boolean = !!route.routeConfig && !!this.storedRoutes[route.routeConfig.path];

        // this decides whether the route already stored should be rendered in place of the requested route, and is the return value
        // at this point we already know that the paths match because the storedResults key is the route.routeConfig.path
        // so, if the route.params and route.queryParams also match, then we should reuse the component
        if (canAttach) {
            let willAttach: boolean = true;
            console.log("param comparison:");
            console.log(this.compareObjects(route.params, this.storedRoutes[route.routeConfig.path].snapshot.params));
            console.log("query param comparison");
            console.log(this.compareObjects(route.queryParams, this.storedRoutes[route.routeConfig.path].snapshot.queryParams));

            let paramsMatch: boolean = this.compareObjects(route.params, this.storedRoutes[route.routeConfig.path].snapshot.params);
            let queryParamsMatch: boolean = this.compareObjects(route.queryParams, this.storedRoutes[route.routeConfig.path].snapshot.queryParams);

            console.log("deciding to attach...", route, "does it match?", this.storedRoutes[route.routeConfig.path].snapshot, "return: ", paramsMatch && queryParamsMatch);
            return paramsMatch && queryParamsMatch;
        } else {
            return false;
        }
    }

    /** 
     * Finds the locally stored instance of the requested route, if it exists, and returns it
     * @param route New route the user has requested
     * @returns DetachedRouteHandle object which can be used to render the component
     */
    retrieve(route: ActivatedRouteSnapshot): DetachedRouteHandle {

        // return null if the path does not have a routerConfig OR if there is no stored route for that routerConfig
        if (!route.routeConfig || !this.storedRoutes[route.routeConfig.path]) return null;
        console.log("retrieving", "return: ", this.storedRoutes[route.routeConfig.path]);

        /** returns handle when the route.routeConfig.path is already stored */
        return this.storedRoutes[route.routeConfig.path].handle;
    }

    /** 
     * Determines whether or not the current route should be reused
     * @param future The route the user is going to, as triggered by the router
     * @param curr The route the user is currently on
     * @returns boolean basically indicating true if the user intends to leave the current route
     */
    shouldReuseRoute(future: ActivatedRouteSnapshot, curr: ActivatedRouteSnapshot): boolean {
        console.log("deciding to reuse", "future", future.routeConfig, "current", curr.routeConfig, "return: ", future.routeConfig === curr.routeConfig);
        return future.routeConfig === curr.routeConfig;
    }

    /** 
     * This nasty bugger finds out whether the objects are _traditionally_ equal to each other, like you might assume someone else would have put this function in vanilla JS already
     * One thing to note is that it uses coercive comparison (==) on properties which both objects have, not strict comparison (===)
     * Another important note is that the method only tells you if `compare` has all equal parameters to `base`, not the other way around
     * @param base The base object which you would like to compare another object to
     * @param compare The object to compare to base
     * @returns boolean indicating whether or not the objects have all the same properties and those properties are ==
     */
    private compareObjects(base: any, compare: any): boolean {

        // loop through all properties in base object
        for (let baseProperty in base) {

            // determine if comparrison object has that property, if not: return false
            if (compare.hasOwnProperty(baseProperty)) {
                switch(typeof base[baseProperty]) {
                    // if one is object and other is not: return false
                    // if they are both objects, recursively call this comparison function
                    case 'object':
                        if ( typeof compare[baseProperty] !== 'object' || !this.compareObjects(base[baseProperty], compare[baseProperty]) ) { return false; } break;
                    // if one is function and other is not: return false
                    // if both are functions, compare function.toString() results
                    case 'function':
                        if ( typeof compare[baseProperty] !== 'function' || base[baseProperty].toString() !== compare[baseProperty].toString() ) { return false; } break;
                    // otherwise, see if they are equal using coercive comparison
                    default:
                        if ( base[baseProperty] != compare[baseProperty] ) { return false; }
                }
            } else {
                return false;
            }
        }

        // returns true only after false HAS NOT BEEN returned through all loops
        return true;
    }
}

行为

此实现存储用户在路由器上访问的每条唯一路由仅一次。这将在用户在站点上的整个 session 期间继续添加到存储在内存中的组件。如果您想限制您存储的路线，可以在 shouldDetach 上进行。方法。它控制您保存哪些路线。

示例

假设您的用户从主页搜索某些内容，然后将他们导航到路径 search/:term , 可能看起来像 www.yourwebsite.com/search/thingsearchedfor .搜索页面包含一堆搜索结果。你想存储这条路线，以防他们想回来!现在他们点击搜索结果并导航到 view/:resultId ，您不想存储它，因为它们可能只会出现一次。有了上面的实现，我只需更改 shouldDetach方法!它可能如下所示:

首先让我们创建一个我们想要存储的路径数组。

private acceptedRoutes: string[] = ["search/:term"];

现在，在 shouldDetach我们可以查看 route.routeConfig.path反对我们的阵列。

shouldDetach(route: ActivatedRouteSnapshot): boolean {
    // check to see if the route's path is in our acceptedRoutes array
    if (this.acceptedRoutes.indexOf(route.routeConfig.path) > -1) {
        console.log("detaching", route);
        return true;
    } else {
        return false; // will be "view/:resultId" when user navigates to result
    }
}

因为 Angular 只会存储一个路由实例，所以这个存储是轻量级的，我们只会存储位于 search/:term 的组件。而不是所有其他人!

附加链接

尽管目前还没有太多文档，但这里有几个链接可以了解现有内容:

Angular 文档: https://angular.io/docs/ts/latest/api/router/index/RouteReuseStrategy-class.html

介绍文章: https://www.softwarearchitekt.at/post/2016/12/02/sticky-routes-in-angular-2-3-with-routereusestrategy.aspx

nativescript-angular 的默认实现 路由重用策略 : https://github.com/NativeScript/nativescript-angular/blob/cb4fd3a/nativescript-angular/router/ns-route-reuse-strategy.ts