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docs(angular-query): Add Optimistic Updates Example for Angular (#8439)
* feat: add optimistic updates example for Angular - Implemented OptimisticUpdatesComponent with Angular Query for managing optimistic UI updates. - Added TasksService to handle query and mutation logic with , , and handlers. - Included mock API interceptor for simulating backend responses. * Remove comment * add lock file * ci: apply automated fixes * fix build, add example to docs * ci: apply automated fixes --------- Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com> Co-authored-by: Arnoud <[email protected]>
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‎docs/config.json

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"label": "Auto Refetching / Polling / Realtime",
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"to": "framework/angular/examples/auto-refetching"
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},
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{
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"label": "Optimistic Updates",
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"to": "framework/angular/examples/optimistic-updates"
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},
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{
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"label": "Pagination",
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"to": "framework/angular/examples/pagination"

‎examples/angular/optimistic-updates/.devcontainer/devcontainer.json

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{
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"name": "Node.js",
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"image": "mcr.microsoft.com/devcontainers/javascript-node:22"
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}

‎examples/angular/optimistic-updates/.eslintrc.cjs

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// @ts-check
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/** @type {import('eslint').Linter.Config} */
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const config = {}
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module.exports = config

‎examples/angular/optimistic-updates/README.md

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# TanStack Query Angular optimistic-updates example
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To run this example:
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- `npm install` or `yarn` or `pnpm i` or `bun i`
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- `npm run start` or `yarn start` or `pnpm start` or `bun start`

‎examples/angular/optimistic-updates/angular.json

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{
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"$schema": "./node_modules/@angular/cli/lib/config/schema.json",
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"version": 1,
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"cli": {
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"packageManager": "pnpm",
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"analytics": false,
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"cache": {
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"enabled": false
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}
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},
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"newProjectRoot": "projects",
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"projects": {
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"optimistic-updates": {
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"projectType": "application",
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"schematics": {
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"@schematics/angular:component": {
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"inlineTemplate": true,
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"inlineStyle": true,
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"skipTests": true
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},
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"@schematics/angular:class": {
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"skipTests": true
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},
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"@schematics/angular:directive": {
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"skipTests": true
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},
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"@schematics/angular:guard": {
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"skipTests": true
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},
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"@schematics/angular:interceptor": {
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"skipTests": true
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},
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"@schematics/angular:pipe": {
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"skipTests": true
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},
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"@schematics/angular:resolver": {
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"skipTests": true
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},
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"@schematics/angular:service": {
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"skipTests": true
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}
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},
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"root": "",
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"sourceRoot": "src",
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"prefix": "app",
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"architect": {
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"build": {
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"builder": "@angular/build:application",
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"options": {
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"outputPath": "dist/optimistic-updates",
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"index": "src/index.html",
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"browser": "src/main.ts",
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"polyfills": ["zone.js"],
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"tsConfig": "tsconfig.app.json",
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"assets": ["src/favicon.ico", "src/assets"],
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"styles": [],
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"scripts": []
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},
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"configurations": {
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"production": {
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"budgets": [
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{
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"type": "initial",
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"maximumWarning": "500kb",
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"maximumError": "1mb"
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},
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{
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"type": "anyComponentStyle",
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"maximumWarning": "2kb",
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"maximumError": "4kb"
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}
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],
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"outputHashing": "all"
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},
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"development": {
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"optimization": false,
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"extractLicenses": false,
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"sourceMap": true
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}
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},
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"defaultConfiguration": "production"
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},
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"serve": {
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"builder": "@angular/build:dev-server",
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"configurations": {
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"production": {
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"buildTarget": "optimistic-updates:build:production"
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},
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"development": {
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"buildTarget": "optimistic-updates:build:development"
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}
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},
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"defaultConfiguration": "development"
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},
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"extract-i18n": {
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"builder": "@angular/build:extract-i18n",
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"options": {
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"buildTarget": "optimistic-updates:build"
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}
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}
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}
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}
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}
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}

‎examples/angular/optimistic-updates/package.json

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{
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"name": "@tanstack/query-example-angular-optimistic-updates",
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"type": "module",
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"scripts": {
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"ng": "ng",
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"start": "ng serve",
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"build": "ng build",
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"watch": "ng build --watch --configuration development"
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},
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"private": true,
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"dependencies": {
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"@angular/common": "^19.1.0-next.0",
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"@angular/compiler": "^19.1.0-next.0",
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"@angular/core": "^19.1.0-next.0",
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"@angular/forms": "19.1.0-next.0",
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"@angular/platform-browser": "^19.1.0-next.0",
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"@angular/platform-browser-dynamic": "^19.1.0-next.0",
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"@tanstack/angular-query-experimental": "^5.66.4",
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"rxjs": "^7.8.1",
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"tslib": "^2.6.3",
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"zone.js": "^0.15.0"
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},
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"devDependencies": {
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"@angular/build": "^19.0.2",
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"@angular/cli": "^19.0.2",
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"@angular/compiler-cli": "^19.1.0-next.0",
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"typescript": "5.7.2"
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}
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}

‎examples/angular/optimistic-updates/src/app/app.component.ts

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import { ChangeDetectionStrategy, Component } from '@angular/core'
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import { OptimisticUpdatesComponent } from './components/optimistic-updates.component'
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@Component({
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changeDetection: ChangeDetectionStrategy.OnPush,
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selector: 'app-root',
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standalone: true,
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template: `<optimistic-updates />`,
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imports: [OptimisticUpdatesComponent],
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})
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export class AppComponent {}

‎examples/angular/optimistic-updates/src/app/app.config.ts

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import {
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provideHttpClient,
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withFetch,
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withInterceptors,
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} from '@angular/common/http'
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import {
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QueryClient,
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provideTanStackQuery,
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withDevtools,
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} from '@tanstack/angular-query-experimental'
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import { mockInterceptor } from './interceptor/mock-api.interceptor'
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import type { ApplicationConfig } from '@angular/core'
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export const appConfig: ApplicationConfig = {
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providers: [
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provideHttpClient(withFetch(), withInterceptors([mockInterceptor])),
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provideTanStackQuery(
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new QueryClient({
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defaultOptions: {
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queries: {
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gcTime: 1000 * 60 * 60 * 24, // 24 hours
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},
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},
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}),
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withDevtools(),
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),
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],
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}

‎examples/angular/optimistic-updates/src/app/components/optimistic-updates.component.ts

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import { ChangeDetectionStrategy, Component, inject } from '@angular/core'
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import {
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injectMutation,
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injectQuery,
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} from '@tanstack/angular-query-experimental'
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import { FormsModule } from '@angular/forms'
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import { DatePipe } from '@angular/common'
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import { TasksService } from '../services/tasks.service'
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@Component({
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changeDetection: ChangeDetectionStrategy.OnPush,
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selector: 'optimistic-updates',
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imports: [FormsModule, DatePipe],
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template: `
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<p>
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In this example, new items can be created using a mutation. The new item
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will be optimistically added to the list in hopes that the server accepts
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the item. If it does, the list is refetched with the true items from the
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list. Every now and then, the mutation may fail though. When that happens,
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the previous list of items is restored and the list is again refetched
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from the server.
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</p>
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<hr />
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@if (tasks.isLoading()) {
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<p>Loading...</p>
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}
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<div class="container">
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<label>
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<input type="checkbox" [(ngModel)]="failMutation" />
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Fail Mutation
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</label>
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<div class="input-container">
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<input type="text" [(ngModel)]="newItem" placeholder="Enter text" />
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<button (click)="addItem()">Create</button>
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<ul>
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@for (task of tasks.data(); track task) {
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<li>{{ task }}</li>
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}
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</ul>
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<div>
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Updated At: {{ tasks.dataUpdatedAt() | date: 'MMMM d, h:mm:ss a ' }}
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</div>
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</div>
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@if (!tasks.isLoading() && tasks.isFetching()) {
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<p>Fetching in background</p>
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}
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</div>
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`,
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})
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export class OptimisticUpdatesComponent {
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#tasksService = inject(TasksService)
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tasks = injectQuery(() => this.#tasksService.allTasks())
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clearMutation = injectMutation(() => this.#tasksService.addTask())
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addMutation = injectMutation(() => this.#tasksService.addTask())
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newItem = ''
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failMutation = false
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addItem() {
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if (!this.newItem) return
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this.addMutation.mutate({
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task: this.newItem,
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failMutation: this.failMutation,
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})
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this.newItem = ''
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}
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}

‎examples/angular/optimistic-updates/src/app/interceptor/mock-api.interceptor.ts

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/**
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* MockApiInterceptor is used to simulate API responses for `/api/tasks` endpoints.
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* It handles the following operations:
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* - GET: Fetches all tasks from sessionStorage.
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* - POST: Adds a new task to sessionStorage.
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* Simulated responses include a delay to mimic network latency.
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*/
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import { HttpResponse } from '@angular/common/http'
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import { delay, of } from 'rxjs'
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import type {
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HttpEvent,
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HttpHandlerFn,
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HttpInterceptorFn,
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HttpRequest,
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} from '@angular/common/http'
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import type { Observable } from 'rxjs'
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export const mockInterceptor: HttpInterceptorFn = (
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req: HttpRequest<unknown>,
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next: HttpHandlerFn,
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): Observable<HttpEvent<any>> => {
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const respondWith = (status: number, body: any) =>
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of(new HttpResponse({ status, body })).pipe(delay(1000))
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if (req.url === '/api/tasks') {
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switch (req.method) {
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case 'GET':
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return respondWith(
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200,
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JSON.parse(
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sessionStorage.getItem('optimistic-updates-tasks') || '[]',
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),
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)
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case 'POST':
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const tasks = JSON.parse(
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sessionStorage.getItem('optimistic-updates-tasks') || '[]',
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)
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tasks.push(req.body)
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sessionStorage.setItem(
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'optimistic-updates-tasks',
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JSON.stringify(tasks),
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)
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return respondWith(201, {
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status: 'success',
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task: req.body,
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})
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}
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}
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if (req.url === '/api/tasks-wrong-url') {
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return respondWith(500, {
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status: 'error',
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})
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}
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return next(req)
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}

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