1. 在 reducers/index.ts 文件中，确保使用的 reducer 函数返回一个合法的 state，且 state 的类型需要和 interface 中声明的一致。

例如：

import { ActionReducerMap } from '@ngrx/store'; import { AppState } from '../models/app-state.model'; import { reducer as productReducer } from './product.reducer'; import { reducer as cartReducer } from './cart.reducer';

export const reducers: ActionReducerMap = { products: productReducer, cart: cartReducer };

2. 在 reducer 函数中，确保所有的 case 分支都返回一个新的 state，而不是修改原先的 state。

例如：

import { ProductActionTypes, ProductActions } from '../actions/product.actions';

export interface ProductState { products: Array; };

export const initialState: ProductState = { products: [] };

export function reducer(state = initialState, action: ProductActions): ProductState { switch (action.type) { case ProductActionTypes.LoadProductsSuccess: { return { ...state, products: action.payload }; } default: { return state; } } }

3. 在使用 reducer 函数的组件中，需要声明当前组件需要订阅的 state 数据，并通过 map 函数将其映射到组件中的变量。

例如：

import { Component, OnInit } from '@angular/core'; import { Store } from '@ngrx/store'; import { ProductState } from '../reducers/product.reducer'; import { LoadProducts } from '../actions/product.actions'; import { Observable } from 'rxjs/Observable'; import { Product } from '../models/product.model';

@Component({ selector: 'app-product-list', templateUrl: './product-list.component.html', styleUrls: ['./product-list.component.css'] }) export class ProductListComponent implements OnInit { products$: Observable>;

constructor(private store: Store) {}

ngOnInit() { this.store.dispatch(new LoadProducts()); this.products$ = this.store.select('products'); }

}

通过以上三个步骤，可以避免在 Angular ngrx store 中出现 reducer 语法问题。