@ngrx 4商店返回类型

Question

我正在创建一个使用Angular 4和@ngrx 4的web应用程序，并且我遇到了Store返回类型的问题。这是在我使用的组件Store：

export class ProductEditComponent implements OnInit, OnDestroy { 

    categoryMap: Map<number, Node>; 
    categoryObs$: Observable<State>; 
    categoryObsSubscription; 

    constructor(private store: Store<State>) { } 

    ngOnInit() { 
    // Retrieve data from the backend. 
    this.categoryObs$ = this.store.select('productTree'); 
    this.categoryObsSubscription = this.categoryObs$.subscribe((res: State) => { 
     this.categoryMap = res.productTree; 
    }, (error) => { 
     console.error(error); 
    }); 

    this.store.dispatch(new productTreeActions.LoadProductTreeAction(1)); 
    } 

    ngOnDestroy() { 
    this.categoryObsSubscription.unsubscribe(); 
    } 

} 

从我能理解的文档，我从store.select获得观察员应键入到State接口，因为我创造了Store为： store: Store<State>

然而，当我尝试我观察到的分配给选定Store（this.categoryObs$ = this.store.select('productTree');），我得到这个错误：

Type 'Store<Map<number, Node>>' is not assignable to type 'Observable<State>'. Types of property 'operator' are incompatible. Type 'Operator<any, Map<number, Node>>' is not assignable to type 'Operator<any, State>'. Type 'Map<number, Node>' is not assignable to type 'State'. Property 'productTree' is missing in type 'Map<number, Node>'. 

我不确定我做错了什么，因为我已经检查了res的值，它对应于State类。

这里是我的终极版：

export interface State { 
    productTree: Map<number, Node>; 
    errorMsg: string; 
} 

const initialState: State = { 
    productTree: new Map<number, Node>(), 
    errorMsg: '' 
}; 

export function productTreeReducer(state = initialState, action: productTreeOperations.Actions): State { 

    switch (action.type) { 
    case productTreeOperations.LOAD_PRODUCT_TREE: 
     return initialState; // Reset state 

    case productTreeOperations.LOAD_PRODUCT_TREE_COMPLETE: 
     return { productTree: action.payload, errorMsg: '' }; 

    case productTreeOperations.LOAD_PRODUCT_TREE_FAIL: 
     return { productTree: undefined, errorMsg: action.payload } 

    case productTreeOperations.DELETE_BRANCH: 
     return deleteBranch(action.payload, state); 

    case productTreeOperations.ADD_CHILD: 
     return addChild(action.payload.parent, action.payload.newChild, state); 

    default: 
     return state; 
    } 
} 

和行动：

export const LOAD_PRODUCT_TREE = 'load-product-tree'; 
export const LOAD_PRODUCT_TREE_COMPLETE = 'load-product-tree-complete'; 
export const LOAD_PRODUCT_TREE_FAIL = 'load-product-tree-fail'; 

export const DELETE_BRANCH = 'delete-branch'; 
export const ADD_CHILD = 'add-child'; 

/** 
* Loads tree from backend and resets current state. 
*/ 
export class LoadProductTreeAction implements Action { 
    readonly type = LOAD_PRODUCT_TREE; 
    constructor (public payload: number) { } 
} 

/** 
* Returns the loaded tree from the backend. 
*/ 
export class LoadProductTreeCompleteAction implements Action { 
    readonly type = LOAD_PRODUCT_TREE_COMPLETE; 
    constructor (public payload: Map<number, Node>) { } 
} 

/** 
* Returns an error that happened when the tree was being loaded from the backend. 
*/ 
export class LoadProductTreeFailAction implements Action { 
    readonly type = LOAD_PRODUCT_TREE_FAIL; 
    constructor (public payload: string) { } 
} 

/** 
* Deletes an entire branch of the tree (the current node and all child nodes). 
*/ 
export class DeleteBranchAction implements Action { 
    readonly type = DELETE_BRANCH; 
    constructor (public payload: Node) { } 
} 

/** 
* Adds a child to a node. 
*/ 
export class AddChildAction implements Action { 
    readonly type = ADD_CHILD; 
    constructor (public payload: { parent: Node, newChild: Node }) { } 
} 

export type Actions = LoadProductTreeAction | 
         LoadProductTreeCompleteAction | 
         LoadProductTreeFailAction | 
         DeleteBranchAction | 
         AddChildAction; 

Answer 1

你的状态由productTree它的类型是Map<number, Node>

export interface State { 
    productTree: Map<number, Node>; 
    errorMsg: string; 
} 

你从商店选择productTree的。

this.categoryObs$ = this.store.select('productTree'); 

因此，它将返回Map<number, Node>而不是Observable<State>。

取而代之，您应该使用createFeatureSelector来返回状态，然后订阅它，如下面的示例。

// reducers.ts 
import { createSelector, createFeatureSelector } from '@ngrx/store'; 

export interface FeatureState { 
    counter: number; 
} 

export interface AppState { 
    feature: FeatureState 
} 

export const selectFeature = createFeatureSelector<FeatureState>('feature'); 

，并使用该selectFeature在组件

store.select(selectFeature).subscribe(store =. { 
    this.counter = store.counter; 
}); 

Read about selectors from here