Result<TError, TValue> (class)

Result is a Either version directly focused in handling errors, it is more specific since TLeft is limited to be an Error.

Status: stable

Factory Methods

Result.left<TError>(error)

Creates a left Either instance with the Error value filled.

Status: stable
Returns: Result<TError, unknown>

Parameters

Name	Type	Description
error	T extends Error	The value to fill the left slot

Example usage

const { Result } = Melon.std.functional;

const error = new Error("The condition is false");
const myValue = condition ? Result.right("The condition is true") : Result.left(error);

Result.right<TValue>(value)

Creates a left Either instance with the Error value filled.

Status: stable
Returns: Result<unknown, TValue>

Parameters

Name	Type	Description
value	T extends Error	The value to fill the left slot

Example usage

const { Result } = Melon.std.functional;

const error = new Error("The condition is false");
const myValue = condition ? Result.right("The condition is true") : Result.left(error);

Instance Methods

Result.match<T>(actionError, actionValue)

Create an a pattern-matching based operation chain to the Result values. This is inherited from Either.

Status: stable
Returns: T

Parameters

Name	Type	Description
actionError	Function	The operation to be called in case of the error not being null
actionValue	Function	The operation to be called in case of the value not being null

Example usage

const { Result } = Melon.std.functional;

const myValue = condition ? Result.right("The condition is true") : Result.left(error);
const myDerivedValue = myValue.match<string>(
    error => error.message,
    value => value
);

Result.fold<T>(actionLeft, actionRight)

Create an a pattern-matching based operation chain to the Result values. This is inherited from Either.

Status: stable
Returns: T

Parameters

Name	Type	Description
actionLeft	Function	The operation to be called in case of the left value not being null
actionRight	Function	The operation to be called in case of the right value not being null

Example usage

const { Result } = Melon.std.functional;

const myValue = condition ? Result.right("The condition is true") : Result.left(error);
const myDerivedValue = myValue.fold<string>(
    error => error.message,
    value => value
);