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// Observer Interface
interface Observer {
  update(steps: number, heartRate: number, sleep: number): void;
}

// Subject Interface
interface Subject {
  registerObserver(observer: Observer): void;
  removeObserver(observer: Observer): void;
  notifyObservers(): void;

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// Step 1: Create the Component Interface
interface Coffee {
  cost(): number;
  description(): string;
}

// Step 2: Implement the Component Interface
class SimpleCoffee implements Coffee {
  cost(): number {
    return 1;

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// Step 1: Define the Interface our System Expects
interface IMessageClient {
  sendMessage(channel: string, user: string, message: string): void;
}

// Step 2: Implement Slack Client (Adaptee)
class SlackClient {
  postMessageToUserInChannel(channel: string, user: string, message: string) {
    console.log(`Posting message to ${user} in ${channel} through Slack: ${message}`);
  }

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// Step 1: Create the Product Class

class GameCharacter {
  name?: string;
  class?: string;
  weapon?: string;
  armor?: string;
  // ... any other game character attributes

  describe() {

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// Step 1: Create a Prototype

// Create a Cloneable interface
interface Cloneable {
  clone(): Cloneable;
}

// Create a GameObject class that implements Cloneable
class GameObject implements Cloneable {
  constructor(private sprite: string, private position: number) {}

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// Step 1: Define the Subsystem Interfaces and Implementation

// Define interfaces
interface LightSystem {
  turnOn(): void;
  turnOff(): void;
}

interface SecuritySystem {
  arm(): void;

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// Step 1: Define the Product Interface
interface Car {
  model: string;
  drive(): void;
}

// Step 2: Implement Concrete Products
class Tesla implements Car {
  model = "Tesla";

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// env.ts

import { z } from 'zod';

const envVariables = z.object({
    DATABASE_URL: z.string();
})

envVariables.parse(process.env);

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import {
  NestInterceptor,
  ExecutionContext,
  Injectable,
  CallHandler,
} from '@nestjs/common';
import { classToPlain } from 'class-transformer';
import { map } from 'rxjs/operators';

@Injectable()

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First Normal Form (INF)

1. Using row order to convey information is not permitted.
2. Mixing data types within the same column is not permitted.
3. Having a table without a primary key is not permitted.
4. Repeating groups are not permitted.

Second Normal Form (2NF)

Each non-key attribute in the table must be dependent on the entire primary key.

Third Normal Form (3NF)

Each non-key attribute in the table must depend on the key, the whole key, and nothing but the key.

Boyce-Codd Normal Form (BCNF)