Lära Reusable Patterns | Advanced Type Patterns and Best Practices

When working with APIs in real-world applications, you often need to handle responses that follow a consistent structure but may contain different types of data. For example, an API might return user data in one response and product data in another, but both responses share common properties like a status code and potential error messages. To avoid rewriting similar types for every endpoint, you can use a reusable, generic API response type that adapts to any kind of data payload.


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// Define a generic interface for API responses
interface ApiResponse<T> {
  data: T | null;
  error: string | null;
  status: number;
}

This ApiResponse<T> interface allows you to specify the type of the data property using a generic parameter. You can use ApiResponse<User> for a user-related endpoint, or ApiResponse<Product> for a product-related endpoint, ensuring type safety and consistency across your codebase. For example, suppose you have the following user and product types:

type User = {
  id: number;
  name: string;
};

type Product = {
  id: number;
  title: string;
  price: number;
};

You can then type your API responses as ApiResponse<User> or ApiResponse<Product>, depending on what data you expect from the server. This pattern helps you avoid duplicating code and makes it easier to manage changes across your application.


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// Example function that fetches user data and returns a typed ApiResponse<User>
async function fetchUser(userId: number): Promise<ApiResponse<User>> {
  try {
    // Simulate fetching user data from an API
    const user: User = { id: userId, name: "Alice" };
    return {
      data: user,
      error: null,
      status: 200,
    };
  } catch (e) {
    return {
      data: null,
      error: "Failed to fetch user",
      status: 500,
    };
  }
}

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              123456
            
// Define a generic interface for API responses
interface ApiResponse<T> {
  data: T | null;
  error: string | null;
  status: number;
}

type User = {
  id: number;
  name: string;
};

type Product = {
  id: number;
  title: string;
  price: number;
};


              123456789101112131415161718
            
// Example function that fetches user data and returns a typed ApiResponse<User>
async function fetchUser(userId: number): Promise<ApiResponse<User>> {
  try {
    // Simulate fetching user data from an API
    const user: User = { id: userId, name: "Alice" };
    return {
      data: user,
      error: null,
      status: 200,
    };
  } catch (e) {
    return {
      data: null,
      error: "Failed to fetch user",
      status: 500,
    };
  }
}

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 1