The match function in Effect-TS is a versatile utility that allows developers to handle cases of Option values (Some and None) in a functional and expressive manner. It provides a way to define actions or computations that should occur based on the presence or absence of a value within an Option. By using match, you can succinctly specify different behaviors for Some and None without the need for explicit conditional checks, thus making your code cleaner and easier to understand. This function enhances code readability and maintainability by encapsulating conditional logic in a declarative style.
Example 1
Match an Option and provide different behaviors for Some and None using O.match.
This example demonstrates returning different messages based on whether the Option contains a value or not.
import { Option as O, pipe } from 'effect'; function match_ex01() { const some = O.some(1); const none = O.none(); const handleOption = O.match({ onNone: () => 'Option is None', onSome: (value) => `Option contains: ${value}`, }); console.log(handleOption(some)); // Output: Option contains: 1 console.log(handleOption(none)); // Output: Option is None
}
Example 2
Match an Option and perform different side effects based on whether it is Some or None.
This example demonstrates logging messages based on the presence of a value.
function match_ex02() { const some = O.some(1); const none = O.none(); pipe( some, O.match({ onNone: () => console.log('Option is None'), // Log a message if the Option is None onSome: (value) => console.log(`Option contains: ${value}`), // Log the value if the Option is Some }) ); // Output: Option contains: 1 pipe( none, O.match({ onNone: () => console.log('Option is None'), // Log a message if the Option is None onSome: (value) => console.log(`Option contains: ${value}`), // Log the value if the Option is Some }) ); // Output: Option is None
}
Example 3
Match an Option and return a default value if it is None using O.match.
This example demonstrates providing a default value for a None case.
function match_ex03() { const some = O.some(1); const none = O.none(); const getValueOrDefault = ( option: O.Option<number>, defaultValue: number ): number => pipe( option, O.match({ onNone: () => defaultValue, // Return the default value if the Option is None onSome: (value) => value, // Return the contained value if the Option is Some }) ); console.log(getValueOrDefault(some, 0)); // Output: 1 (since some contains 1) console.log(getValueOrDefault(none, 0)); // Output: 0 (since none is None)
}
Example 4
Match an Option and perform computations based on the contained value using O.match.
This example demonstrates different computations based on the presence of a value.
function match_ex04() { const some = O.some(2); const none = O.none(); const compute = O.match({ onNone: () => 0, // Return 0 if the Option is None onSome: (value: number) => value * value, // Compute the square of the value if the Option is Some }); console.log(compute(some)); // Output: 4 (since some contains 2 and 2*2 = 4) console.log(compute(none)); // Output: 0 (since none is None)
}
Example 5
Match an Option with more complex types and return a message based on the presence of a value.
This example demonstrates matching an Option containing an object.
function match_ex05() { const some = O.some({ key: 'value' }); const none = O.none(); const handleComplexOption = O.match<string, { key: string }>({ onNone: () => 'No data available', // Return a message if the Option is None onSome: (obj) => `Data: ${obj.key}`, // Return the key of the object if the Option is Some }); console.log(handleComplexOption(some)); // Output: Data: value console.log(handleComplexOption(none)); // Output: No data available
}
Conclusion
In conclusion, the match function is an essential tool in the Effect-TS library that simplifies handling optional values with the Option type. By providing clear, type-safe ways to distinguish between Some and None, match helps avoid common errors associated with null checks and enhances the functional programming capabilities in TypeScript. As demonstrated through various examples, using match not only makes the code more robust but also significantly improves its readability and expressiveness. Adopting this pattern can lead to cleaner, more maintainable codebases where optional values are a common occurrence.
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