[英]How can I effectively reset a state using @ngrx/store?
最近几天我似乎被这个问题困住了。
我们正在开发一个 Angular 2 应用程序,我需要为用户创建一个向导来填写表单。
我已经成功地使数据流过向导的每个步骤,并保存它以便自由来回移动。 但是,一旦提交表单,我似乎无法重置它。
我应该补充一点,每个组件都在墙后。 也许更好的解决方案是在 AppModule 中直接注入单例服务。 但我似乎无法让它发挥作用。
到目前为止,这是我的代码:
第1步
import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { Router } from '@angular/router';
import { EventOption } from '../../../events/shared/event-option.model';
import { Store } from '@ngrx/store';
import { NewEventService } from '../shared/new-event.service';
import { Event } from '../../../events/shared/event.model';
import { FriendService } from '../../../friends/shared/friend.service';
@Component({
selector: 'app-upload-images',
templateUrl: './upload-images.component.html',
styleUrls: ['../../../events/new-event/new-event.component.css']
})
export class UploadImagesComponent implements OnInit {
form: FormGroup;
private event;
private images = [];
constructor(
private _store: Store<any>,
private formBuilder: FormBuilder,
private router: Router,
private newEventService: NewEventService,
private friendService: FriendService
) {
_store.select('newEvent').subscribe(newEvent => {
this.event = newEvent;
})
}
ngOnInit() {
this.initForm(this.event);
if (this.event.counter === 0) {
let friends = this.friendService.getFriends('58aaf6304fabf427e0acc08d');
for (let friend in friends) {
this.event.userIds.push(friends[friend]['id']);
}
}
}
initForm(event: Event) {
this.images.push({ imageUrl: 'test0', voteCount: 0 });
this.images.push({ imageUrl: 'test1', voteCount: 0 });
this.images.push({ imageUrl: 'test2', voteCount: 0 });
this.images.push({ imageUrl: 'test3', voteCount: 0 });
this.form = this.formBuilder.group({
firstImage: [this.event.length > 0 ? this.event.eventOption[0].imageUrl : null],
secondImage: [this.event.length > 0 ? this.event.eventOption[1].imageUrl : null],
thirdImage: [this.event.length > 0 ? this.event.eventOption[2].imageUrl : null],
fourthImage: [this.event.length > 0 ? this.event.eventOption[3].imageUrl : null],
})
}
next() {
this.event.eventOptions = this.images;
this.newEventService.updateEvent(this.event);
this.router.navigate(['events/new-event/choose-friends']);
}
}
第2步
import { Component, OnInit, Input } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { Router } from '@angular/router';
import { EventOption } from '../../../events/shared/event-option.model';
import { Store } from '@ngrx/store';
import { Event } from '../../shared/event.model';
import { NewEventService } from '../shared/new-event.service';
import { FriendService } from '../../../friends/shared/friend.service';
import { SearchPipe } from '../../../core/search.pipe';
@Component({
selector: 'app-choose-friends',
templateUrl: './choose-friends.component.html',
styleUrls: ['../../../events/new-event/new-event.component.css', './choose-friends.component.css']
})
export class ChooseFriendsComponent implements OnInit {
private searchTerm = '';
private event;
private friends = [];
private friendsError = false;
constructor(
private _store: Store<any>,
private formBuilder: FormBuilder,
private router: Router,
private newEventService: NewEventService,
private friendService: FriendService
) {
_store.select('newEvent').subscribe(newEvent => {
this.event = newEvent;
})
}
ngOnInit() {
this.friends = this.friendService.getFriends('58aaf6304fabf427e0acc08d');
}
selectedFriend(friendId: string) {
return this.friendService.selectedFriend(friendId, this.event.userIds);
}
toggleFriend(friendId: string) {
return this.friendService.toggleFriend(friendId, this.event.userIds);
}
toggleAllFriends() {
return this.friendService.toggleAllFriends(this.friends, this.event.userIds);
}
submit() {
if (this.event.userIds.length > 0) {
this.newEventService.resetEvent();
this.router.navigate(['events/vote-events']);
} else {
this.friendsError = true;
}
}
back() {
this.newEventService.updateEvent(this.event);
this.router.navigate(['events/new-event/upload-images']);
}
}
活动服务
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Store, Action } from '@ngrx/store';
import { Event } from '../../../events/shared/event.model';
import { EventOption } from '../../../events/shared/event-option.model';
import { newEvent, newEventModel } from './new-event.reducer';
import 'rxjs/add/operator/take';
import 'rxjs/add/operator/find';
import { Subject } from 'rxjs/Subject';
@Injectable()
export class NewEventService {
public newEvent$: Observable<newEventModel>;
constructor(private store: Store<newEventModel>) {
this.newEvent$ = this.store.select('newEvent');
}
getEvent(event) {
return this.store.dispatch({
type: 'GET_EVENT',
payload: event
})
}
updateEvent(event) {
return this.store.dispatch({
type: 'UPDATE_EVENT',
payload: event
})
}
resetEvent() {
return this.store.dispatch({
type: 'RESET_EVENT',
})
}
}
事件减少器
import { EventOption } from '../../shared/event-option.model';
import { EventType } from '../../shared/event-type.model';
import { ActionReducer, Action } from '@ngrx/store';
import { Event } from '../../shared/event.model';
import { FriendService } from '../../../friends/shared/friend.service';
export interface newEventModel {
eventOptions: EventOption[];
eventTypeId: number,
duration: number,
comment: string,
privacyId: number,
isGlobal: boolean,
id: string,
userIds: string[],
counter: number
}
let blankState: newEventModel = {
eventOptions: [],
eventTypeId: null,
duration: 1440,
comment: '',
privacyId: 0,
isGlobal: false,
id: '',
userIds: [],
counter: 0
}
let initialState: newEventModel = {
eventOptions: [],
eventTypeId: null,
duration: 1440,
comment: '',
privacyId: 0,
isGlobal: false,
id: '',
userIds: [],
counter: 0
}
export const newEvent: ActionReducer<newEventModel> = (state: newEventModel = initialState, action: Action) => {
// return new state
switch (action.type) {
case 'GET_EVENT':
return state;
case 'UPDATE_EVENT':
action.payload.counter = action.payload.counter + 1;
return action.payload;
case 'RESET_EVENT':
return Object.assign({}, state, {
eventOptions: [],
eventTypeId: null,
duration: 1440,
comment: '',
privacyId: 0,
isGlobal: false,
id: '',
userIds: [],
counter: 0
});
default:
return state;
}
}
如果需要,我可以提供一个有效的 plunkr,但我需要先创建它。
TLDR:如何重置@ngrx/store 上的状态?
感谢您提供的任何帮助!
您可以通过使用Object.assign
将initialState
所有属性复制到新对象,从而在您的减速器中将状态重置为initialState
。
export const newEvent: ActionReducer<newEventModel> = (state: newEventModel = initialState, action: Action) => {
// return new state
switch (action.type) {
// ...
case 'RESET_EVENT':
return Object.assign({}, initialState);
// ...
}
}
reducer 应该是一个纯函数,所以不应该修改参数。 您的UPDATE_EVENT
需要稍作调整:
case 'UPDATE_EVENT':
let counter = { counter: action.payload.counter + 1 };
return Object.assign({}, action.payload, counter);
到后续的图案是Object.assign({}, source1, source2, ...)
其中source1
, source2
等包含要分配的属性。 在属性source1
是由重复的属性覆盖source2
等。
有更简单的方法,您只需要设置initialState
而不是state
:
const reducer = createReducer(initialState,
on(proofActions.cleanAdditionalInsuredState, (state, action) => ({
...initialState
})),
Noy Levi 对这个问题的回答是正确的,它将initialState 分配回状态,但是,有一种方法可以自动为每个reducer 分配initialState。
要理解的关键概念是,如果传递给减速器的“状态”的值是“未定义”(不是“空”,它需要是“未定义”),那么减速器将自动将提供给的初始状态分配给“状态”减速器创建时。 由于这种默认行为,您可以创建一个识别动作的“元减速器”,例如“注销”,然后将“未定义”状态传递给所有后续调用的减速器。
这篇关于 redux 的文章、 这篇关于 NgRx 的文章以及关于 NgRx 的这个答案中都很好地描述了这种行为。
相关代码如下所示:
export function logoutClearState(reducer) {
return function (state, action) {
if (action.type === ActionTypes.LOGOUT) {
state = undefined;
}
return reducer(state, action);
};
}
@NgModule({
imports: [
StoreModule.forRoot(reducers, { metaReducers: [logoutClearState] }),
],
declarations: [],
providers: [],
})
我假设您的 RESET_EVENT 应该返回一个新对象。 尽管您正在使用state
数据和另一个对象填充对象:
case 'RESET_EVENT':
return Object.assign({}, state, {
eventOptions: [],
eventTypeId: null,
duration: 1440,
comment: '',
privacyId: 0,
isGlobal: false,
id: '',
userIds: [],
counter: 0
});
Object.assign
的语法是Object.assign(target, ...sources)
并且您提供两个项目作为源: state
和包含eventOptions
、 eventTypeId
等的对象。
相反,您需要返回Object.assign({}, initialState);
对不起,我请了一天假为了准备一些考试。 我最终通过执行以下操作来“解决”它:
....
case 'RESET_EVENT':
action.payload.eventOptions = blankState.eventOptions;
action.payload.eventTypeId = blankState.eventTypeId;
action.payload.duration = blankState.duration;
action.payload.comment = blankState.comment;
action.payload.privacyId = blankState.privacyId;
....
return action.payload;
....
它可能不是最漂亮或最好的解决方案,但至少它有效。 感谢@iblamefish 和所有人的帮助。
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