Implementing State Management

import { Injectable } from "@angular/core";
import { BehaviorSubject, Observable } from "rxjs";

export interface AppState {
  user: string | null;
  theme: "light" | "dark";
}

@Injectable({
  providedIn: "root"
})
export class StateService {
  private stateSubject = new BehaviorSubject<AppState>({
    user: null,
    theme: "light"
  });

  public readonly state$ = this.stateSubject.asObservable();

  public updateState(newState: Partial<AppState>) {
    const currentState = this.stateSubject.value;
    this.stateSubject.next({ ...currentState, ...newState });
  }
}

import { Component, OnInit, OnDestroy } from "@angular/core";
import { StateService, AppState } from "./state.service";

@Component({
  selector: "app-example",
  template: `
    <p>Current user: {{ state?.user }}</p>
    <button (click)="toggleTheme()">Toggle Theme</button>
  &#x60;
})
export class ExampleComponent implements OnInit, OnDestroy {
  public state: AppState | null = null;

  constructor(private stateService: StateService) {}

  ngOnInit() {
    this.stateService.state$.subscribe(state => {
      this.state = state;
    });
  }

  toggleTheme() {
    this.stateService.updateState({
      theme: this.state?.theme === "light" ? "dark" : "light"
    });
  }

  ngOnDestroy() {
    // No explicit cleanup needed for observables in this example
  }
}

import { Observable } from 'rxjs';

const myObservable = new Observable(subscriber => {
  subscriber.next('Hello');
  subscriber.next('World');
  subscriber.complete();
});

myObservable.subscribe({
  next: value => console.log(value),
  complete: () => console.log('Finished')
});

import { Events } from 'ionic-angular';
import { Observable } from 'rxjs';

const eventObservable = new Observable(subscriber => {
  const handler = (data) => subscriber.next(data);
  this.events.subscribe('myEvent', handler);

  return () => this.events.unsubscribe('myEvent', handler);
});

eventObservable.subscribe(data => {
  console.log('Received event data:', data);
});

import { BehaviorSubject } from 'rxjs';

export class UserStateService {
  private userSubject = new BehaviorSubject<any>(null);
  public user$ = this.userSubject.asObservable();

  setUser(user: any) {
    this.userSubject.next(user);
  }

  getCurrentUser() {
    return this.userSubject.getValue();
  }
}

import { Component, Input, Output, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-child',
  template: &#x27;<button (click)="onButtonClicked()">{{ title }}</button>&#x27;
})
export class ChildComponent {
  @Input() title: string = &#x27;Default Title&#x27;;
  @Output() onButtonClick = new EventEmitter<string>();

  onButtonClicked() {
    this.onButtonClick.emit(this.title);
  }
}

@Component({
  selector: &#x27;app-parent&#x27;,
  template: &#x27;<app-child [title]="buttonTitle" (onButtonClick)="handleClick($event)"></app-child>&#x27;
})
export class ParentComponent {
  buttonTitle = &#x27;Click Me&#x27;;

  handleClick(event: string) {
    console.log("Button clicked with title:", event);
  }
}

import { createStore } from 'redux';

// Initial state
const initialState = {
  count: 0
};

// Reducer function
function counterReducer(state = initialState, action) {
  switch (action.type) {
    case 'INCREMENT':
      return { ...state, count: state.count + 1 };
    default:
      return state;
  }
}

// Create store
const store = createStore(counterReducer);

// Dispatch action
store.dispatch({ type: 'INCREMENT' });

console.log(store.getState()); // { count: 1 }

const setUser = (userData) => ({
  type: 'SET_USER_DATA',
  payload: userData
});

const userReducer = (state = {}, action) => {
  switch (action.type) {
    case 'SET_USER_DATA':
      return { ...state, ...action.payload };
    default:
      return state;
  }
};

import { setUser } from './actions';

// Dispatch the action
dispatch(setUser({ name: 'Alice', role: 'admin' }));

import { select } from '@angular/core';
import { Store } from '@ngrx/store';

const user = select(state => state.user);
const posts = select(state => state.posts);

// In component
this.store.select(user).subscribe(user => {
  console.log('User:', user);
});

this.store.select(posts).subscribe(posts => {
  console.log('Posts:', posts);
});

import { call, put, takeEvery } from 'redux-saga/effects';\n\nfunction* fetchUserSaga(action) {\n  try {\n    const user = yield call(fetch, `/api/users/${action.userId}`);\n    yield put({ type: 'FETCH_USER_SUCCESS', user });\n  } catch (error) {\n    yield put({ type: 'FETCH_USER_FAILURE', error });\n  }\n}\n\nfunction* watchFetchUser() {\n  yield takeEvery('FETCH_USER_REQUEST', fetchUserSaga);\n}

import { Injectable } from '@angular/core';\nimport { Actions, createEffect, ofType } from '@ngrx/effects';\nimport { Store } from '@ngrx/store';\nimport { tap, withLatestFrom } from 'rxjs/operators';\n\n@Injectable()\nexport class StorageEffects {\n  saveToStorage$ = createEffect(() =>\n    this.actions$.pipe(\n      ofType('SAVE_STATE'),\n      withLatestFrom(this.store),\n      tap(([action, state]) => {\n        localStorage.setItem('appState', JSON.stringify(state));\n      })\n    ),\n    { dispatch: false }\n  );\n\n  constructor(\n    private actions$: Actions,\n    private store: Store\n  ) {}\n}

import React, { createContext, useContext } from 'react';

const ThemeContext = createContext();

function ThemeProvider({ children }) {
  const [theme, setTheme] = React.useState('light');
  return (
    <ThemeContext.Provider value={{ theme, setTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

function ThemedButton() {
  const { theme, setTheme } = useContext(ThemeContext);
  return (
    <button onClick={() => setTheme(theme === 'light' ? 'dark' : 'light')}>
      {theme} Mode
    </button>
  );
}

import { EventBus } from '@ionic/core';

// Emit an event
EventBus.emit('app:loaded', { timestamp: Date.now() });

// Listen for an event
const handler = (payload) => {
  console.log('App loaded at:', payload.timestamp);
};

EventBus.on('app:loaded', handler);

// Remove listener
EventBus.off('app:loaded', handler);