Detailed explanation of angular learning state manager NgRx

// angular.json
"cli": {
  "defaultCollection": "@ngrx/schematics"
}

import { createAction } from "@ngrx/store"

export const increment = createAction("increment")
export const decrement = createAction("decrement")

import { createReducer, on } from "@ngrx/store"
import { decrement, increment } from "../actions/counter.actions"

export const counterFeatureKey = "counter"

export interface State {
  count: number
}

export const initialState: State = {
  count: 0
}

export const reducer = createReducer(
  initialState,
  on(increment, state => ({ count: state.count + 1 })),
  on(decrement, state => ({ count: state.count - 1 }))
)

import { createFeatureSelector, createSelector } from "@ngrx/store"
import { counterFeatureKey, State } from "../reducers/counter.reducer"
import { AppState } from ".."

export const selectCounter = createFeatureSelector<AppState, State>(counterFeatureKey)
export const selectCount = createSelector(selectCounter, state => state.count)

import { select, Store } from "@ngrx/store"
import { Observable } from "rxjs"
import { AppState } from "./store"
import { decrement, increment } from "./store/actions/counter.actions"
import { selectCount } from "./store/selectors/counter.selectors"

export class AppComponent {
  count: Observable<number>
  constructor(private store: Store<AppState>) {
    this.count = this.store.pipe(select(selectCount))
  }
  increment() {
    this.store.dispatch(increment())
  }
  decrement() {
    this.store.dispatch(decrement())
  }
}

<button (click)="increment()">+</button>
<span>{{ count | async }}</span>
<button (click)="decrement()">-</button>

this.store.dispatch(increment({ count: 5 }))

import { createAction, props } from "@ngrx/store"
export const increment = createAction("increment", props<{ count: number }>())

export declare function props<P extends object>(): Props<P>;

export const reducer = createReducer(
  initialState,
  on(increment, (state, action) => ({ count: state.count + action.count }))
)

function debug(reducer: ActionReducer<any>): ActionReducer<any> {
  return function (state, action) {
    return reducer(state, action)
  }
}

export const metaReducers: MetaReducer<AppState>[] = !environment.production
  ? [debug]
  : []

<button (click)="increment_async()">async</button>

increment_async() {
  this.store.dispatch(increment_async())
}

export const increment_async = createAction("increment_async")

import { Injectable } from "@angular/core"
import { Actions, createEffect, ofType } from "@ngrx/effects"
import { increment, increment_async } from "../actions/counter.actions"
import { mergeMap, map } from "rxjs/operators"
import { timer } from "rxjs"

// createEffect
// 用于创建 Effect, Effect 用于执行副作用.
// 调用方法时传递回调函数, 回调函数中返回 Observable 对象, 对象中要发出副作用执行完成后要触发的 Action 对象
// 回调函数的返回值在 createEffect 方法内部被继续返回, 最终返回值被存储在了 Effect 类的属性中
// NgRx 在实例化 Effect 类后, 会订阅 Effect 类属性, 当副作用执行完成后它会获取到要触发的 Action 对象并触发这个 Action

// Actions
// 当组件触发 Action 时, Effect 需要通过 Actions 服务接收 Action, 所以在 Effect 类中通过 constructor 构造函数参数的方式将 Actions 服务类的实例对象注入到 Effect 类中
// Actions 服务类的实例对象为 Observable 对象, 当有 Action 被触发时, Action 对象本身会作为数据流被发出

// ofType
// 对目标 Action 对象进行过滤.
// 参数为目标 Action 的 Action Creator 函数
// 如果未过滤出目标 Action 对象, 本次不会继续发送数据流
// 如果过滤出目标 Action 对象, 会将 Action 对象作为数据流继续发出

@Injectable()
export class CounterEffects {
  constructor(private actions: Actions) {
    // this.loadCount.subscribe(console.log)
  }
  loadCount = createEffect(() => {
    return this.actions.pipe(
      ofType(increment_async),
      mergeMap(() => timer(1000).pipe(map(() => increment({ count: 10 }))))
    )
  })
}

/*
	{
		ids: [1, 2],
		entities: {
			1: { id: 1, title: "Hello Angular" },
			2: { id: 2, title: "Hello NgRx" }
		}
	}
*/
export interface State extends EntityState<Todo> {}

export const adapter: EntityAdapter<Todo> = createEntityAdapter<Todo>()
// 获取初始状态 可以传递对象参数 也可以不传
// {ids: [], entities: {}}
export const initialState: State = adapter.getInitialState()

// selectTotal 获取数据条数
// selectAll 获取所有数据 以数组形式呈现
// selectEntities 获取实体集合 以字典形式呈现
// selectIds 获取id集合, 以数组形式呈现
const { selectIds, selectEntities, selectAll, selectTotal } = adapter.getSelectors();

export const selectTodo = createFeatureSelector<AppState, State>(todoFeatureKey)
export const selectTodos = createSelector(selectTodo, selectAll)

import { StoreRouterConnectingModule } from "@ngrx/router-store"

@NgModule({
  imports: [
    StoreRouterConnectingModule.forRoot()
  ]
})
export class AppModule {}

import * as fromRouter from "@ngrx/router-store"

export interface AppState {
  router: fromRouter.RouterReducerState
}
export const reducers: ActionReducerMap<AppState> = {
  router: fromRouter.routerReducer
}

// router.selectors.ts
import { createFeatureSelector } from "@ngrx/store"
import { AppState } from ".."
import { RouterReducerState, getSelectors } from "@ngrx/router-store"

const selectRouter = createFeatureSelector<AppState, RouterReducerState>(
  "router"
)

export const {
  // 获取和当前路由相关的信息 (路由参数、路由配置等)
  selectCurrentRoute,
  // 获取地址栏中 # 号后面的内容
  selectFragment,
  // 获取路由查询参数
  selectQueryParams,
  // 获取具体的某一个查询参数 selectQueryParam(&#39;name&#39;)
  selectQueryParam,
  // 获取动态路由参数
  selectRouteParams,
 	// 获取某一个具体的动态路由参数 selectRouteParam(&#39;name&#39;)
  selectRouteParam,
  // 获取路由自定义数据
  selectRouteData,
  // 获取路由的实际访问地址
  selectUrl
} = getSelectors(selectRouter)