Types of parameters 'action' and 'action' are incompatible, Property 'payload' is missing In Angular ngrx

Question

I am new to angular. Here I using ngrx to manage a state in my angular app. But when I'm compiling I got the following error. It says that 'Types of parameters 'action' and 'action' are incompatible'. I want to know the reason for this and how to solve this?

 
    Error: src/app/shopping-list/store/shoppingList.actions.ts:9:5 - error TS2564: Property 'payload' has no initializer and is not definitely assigned in the constructor.
    
    9     payload: Ingredient;
          ~~~~~~~
    src/app/app.module.ts:25:27 - error TS2322: Type '(state: { ingredients: Ingredient[]; } | undefined, action: AddIngredient) => { ingredients: Ingredient[]; }' is not assignable to type 'ActionReducer<{ ingredients: Ingredient[]; }, Action>'.
      Types of parameters 'action' and 'action' are incompatible.
        Property 'payload' is missing in type 'Action' but required in type 'AddIngredient'.
    
    25     StoreModule.forRoot({ shoppingList: shoppingListReducer }),
                                 ~~~~~~~~~~~~
    
      src/app/shopping-list/store/shoppingList.actions.ts:9:5
        9     payload: Ingredient;
              ~~~~~~~
        'payload' is declared here.

This is my shoppingList.actions.ts file.

import { Action } from '@ngrx/store'

import { Ingredient } from '../../shared/ingredient.model';

export const ADD_INGREDIENT = 'ADD_INGREDIENT';

export class AddIngredient implements Action {
    readonly type = ADD_INGREDIENT;
    payload: Ingredient;
}

This is the shoppingList.reducer.ts file.

import { Ingredient } from "src/app/shared/ingredient.model";

import * as shoppingListActions from './shoppingList.actions';

const intialState = {
    ingredients: [
        new Ingredient("Apples", 3),
        new Ingredient("Tomatoes", 4)
    ]
}

export function shoppingListReducer(state = intialState, action: shoppingListActions.AddIngredient) {
    switch (action.type) {
        case shoppingListActions.ADD_INGREDIENT:
            return {
                ...state,
                ingredients: [...state.ingredients, action.payload]
            }
        default:
            return state;
    }
}

Here is my app.module.ts file.

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppRouting } from './app-routing.module';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { HttpClientModule } from '@angular/common/http';
import { StoreModule } from '@ngrx/store';

import { AppComponent } from './app.component';
import { HeaderComponent } from './header/header.component';
import { SharedModule } from './shared/shared.module';
import { CoreModule } from './core.module';
import { shoppingListReducer } from './shopping-list/store/shoppingLis.reducer';

@NgModule({
  declarations: [
    AppComponent,
    HeaderComponent,

  ],
  imports: [
    BrowserModule,
    FormsModule,
    ReactiveFormsModule,
    HttpClientModule,
    StoreModule.forRoot({ shoppingList: shoppingListReducer }),
    AppRouting,
    SharedModule,
    CoreModule,
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

Answer 1

你的问题是因为签名问题，

方法 StoreModule.forRoot<unknown, Action>(reducers: ActionReducerMap<unknown, Action>)

从技术上讲，您正在传递一个正确的参数，但它仍然说您的Action对象参数包含一个字段调用有效负载，它不存在于ActionReducerMap<unknown, Action> 的Action参数中。从技术上讲，它不应该是错误，因为您已经将Action继承到您的操作类

类 AddIngredient 实现 Action{

但不幸的是，很明显ActionReducerMap<unknown, Action>中的Action不是来自'@ngrx/store'或者它们不相同，因此给出了编译错误。

由于您没有任何其他选择，您必须像下面那样修复它：-

首先创建国象下面这样在你购物，list.reducer.ts

export interface ShoppingListState{
    ingredients: Ingredient[];
}

const initialState: ShoppingListState = {
    ingredients: [
        new Ingredient('Apples', 5),
        new Ingredient("Tomatoes", 4),
    ]
};

还要修改您的减速器方法，如下所示：-

export function shoppingListReducer(state: ShoppingListState = initialState, 
    action: shoppingListActions.AddIngredient): ShoppingListState {
    switch(action.type){

现在在您的操作文件夹下创建一个文件调用index.ts（在减速器文件的同一位置 - 您也可以提供不同的名称），如下所示

import { ShoppingListState,  shoppingListReducer } from './shopping-list.reducer';
import { ActionReducerMap } from '@ngrx/store';


export const rootReducer = {};

export interface AppState {
    shoppingList: ShoppingListState;
};


export const reducers: ActionReducerMap<AppState, any> = {
    shoppingList: shoppingListReducer
};

现在将此减速器导入您的app.module.ts

import { reducers } from './reducers/'

并修改您的代码，如下所示

StoreModule.forRoot(reducers)

还要尽量避免像下面这样声明变量。

payload: Ingredient;

更好地使用构造函数并修改您的代码，如下所示：-

export class AddIngredient implements Action {
    readonly type = ADD_INGREDIENT;
    constructor(public payload: Ingredient){}
}

希望这会解决您的问题。