Cast result query mysql2 to type

When working with TypeScript and MySQL, you may come across a situation where you need to cast the result of a query from the mysql2 library to a specific type. This can be useful when you want to ensure type safety and avoid runtime errors. In this blog post, we will explore different solutions to cast the result of a query in TypeScript.

Solution 1: Using Type Assertion

One way to cast the result of a query is by using type assertion. Type assertion allows you to explicitly specify the type of a value, even if TypeScript cannot infer it automatically. Here’s an example:

// Assuming you have a connection to the MySQL database
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: 'password',
  database: 'mydatabase',
});

// Perform the query
connection.query('SELECT * FROM users', (error, results) => {
  if (error) throw error;

  // Cast the result to the desired type
  const users: User[] = results as User[];

  // Use the result
  console.log(users);
});

// Define the User type
interface User {
  id: number;
  name: string;
  email: string;
}

In this example, we assume that you have a connection to the MySQL database using the mysql2 library. After performing the query, we cast the results to the User[] type using the as keyword. This tells TypeScript that we expect the result to be an array of User objects. You can then use the result as a strongly-typed array of users.

Solution 2: Using a Mapper Function

Another approach is to use a mapper function to transform the result of the query into the desired type. This can be useful when you need to perform additional transformations or validations on the data. Here’s an example:

// Assuming you have a connection to the MySQL database
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: 'password',
  database: 'mydatabase',
});

// Perform the query
connection.query('SELECT * FROM users', (error, results) => {
  if (error) throw error;

  // Map the result to the desired type
  const users: User[] = results.map(mapUser);

  // Use the result
  console.log(users);
});

// Define the User type
interface User {
  id: number;
  name: string;
  email: string;
}

// Mapper function
function mapUser(result: any): User {
  return {
    id: result.id,
    name: result.name,
    email: result.email,
  };
}

In this example, we define a mapper function called mapUser that takes a result object and transforms it into a User object. We then use the map function to apply the mapper function to each result in the array. This allows us to create an array of User objects from the query result.

Both solutions provide a way to cast the result of a query from the mysql2 library to a specific type in TypeScript. Choose the solution that best fits your needs and coding style.

That’s it! You now know how to cast the result of a query from mysql2 to a specific type in TypeScript. Happy coding!

Cast result query mysql2 to type