Result Reference

A Result represents either success (Ok) or failure (Err), used for error handling without exceptions.

Result is an abstract base class with two concrete subclasses:

• Ok - represents a successful value
• Err- represents an error value

var success = Ok(42);
var failure = Err("Something went wrong");

Methods

err

Returns the error value if Err, otherwise returns nil.

var result = Err("Something went wrong");
println(result.err()); // "Something went wrong"

var success = Ok(42);
println(success.err()); // nil

Parameters

None

Returns

dyn! - The error value or nil

expect

Returns the success value if Ok, otherwise panics with a custom message.

var result = Ok(42);
var value = result.expect("Expected a valid number"); // 42

var error = Err("original error");
// var value = error.expect("Custom error message"); // Panics with "Custom error message"

Parameters

• message: String - The error message to display if the result is Err

Returns

dyn! - The success value

Throws

Throws with the provided message if the result is Err

flat_map

Transforms the success value with a function that returns a Result, otherwise returns the error unchanged.

var result = Ok(5);
var new_result = result.flat_map((x) -> Ok(x * 2)); // Ok(10)

var error = Err("error");
var still_error = error.flat_map((x) -> Ok(x * 2)); // Err("error")

Parameters

• transform: (dyn!) -> Result - A function that takes the success value and returns a new Result

Returns

Result - The result from the transform function, or the original error

if_err

Calls the provided function if the Result is Err.

var result = Err("error");
var maybe_value = result.if_err((err) -> println(err));

Parameters

callback: (dyn!) -> nil - A callback that will be called if the Result is Err.

Returns

Result - The instance of the Result object.

if_ok

Calls the provided function if the Result is Ok.

var result = Ok("Message");
var maybe_value = result.if_ok((message) -> println(message));

Parameters

callback: (dyn!) -> nil - A callback that will be called if the Result is Ok.

Returns

Result - The instance of the Result object.

is_err

Returns true if the result is Err.

var result = Err("error");
println(result.is_err()); // true

Parameters

None

Returns

Boolean - true if the result is Err, false otherwise

is_ok

Returns true if the result is Ok.

var result = Ok(42);
println(result.is_ok()); // true

Parameters

None

Returns

Boolean - true if the result is Ok, false otherwise

map

Transforms the success value if Ok, otherwise returns the error unchanged.

var result = Ok(5);
var doubled = result.map((x) -> x * 2); // Ok(10)

var error = Err("error");
var still_error = error.map((x) -> x * 2); // Err("error")

Parameters

• transform: (dyn!) -> dyn! - A function that transforms the success value

Returns

Result - A new Result with the transformed value, or the original error

map_err

Transforms the error value if Err, otherwise returns the success unchanged.

var result = Ok(42);
var still_ok = result.map_err((err) -> "New " + err); // Ok(42)

var error = Err("error");
var new_error = error.map_err((err) -> "New " + err); // Err("New error")

Parameters

• transform: (dyn!) -> Err - A function that transforms the error value

Returns

Result - The original success, or a new Result with the transformed error

ok

Returns the success value if Ok, otherwise returns nil.

var result = Ok(42);
println(result.ok()); // 42

var error = Err("error");
println(error.ok()); // nil

Parameters

None

Returns

dyn! - The success value or nil

or_else

Returns the current result if Ok, otherwise calls the provided function and returns its result.

var result = Ok(42);
var new_result = result.or_else(() -> Ok(0)); // Ok(42)

var error = Err("error");
var new_result = error.or_else(() -> Ok(0)); // Ok(0)

Parameters

• callback: () -> Result - A function that returns a new Result

Returns

Result - The current result if Ok, or the result from the callback

unwrap

Returns the success value if Ok, otherwise panics with the error value.

var result = Ok(42);
var value = result.unwrap(); // 42

var error = Err("error");
// var value = error.unwrap(); // Panics with "error"!

Parameters

None

Returns

dyn! - The success value

Throws

Throws if the result is Err, displaying the error value

unwrap_or

Returns the success value if Ok, otherwise returns the provided default value.

var result = Ok(42);
var value = result.unwrap_or(0); // 42

var error = Err("error");
var value = error.unwrap_or(0); // 0

Parameters

• default_value: dyn! - The value to return if the result is Err

Returns

dyn! - The success value or the default value

unwrap_or_else

Returns the success value if Ok, otherwise calls the provided function and returns its result.

var result = Ok(42);
var value = result.unwrap_or_else(() -> 0); // 42

var error = Err("error");
var value = error.unwrap_or_else(() -> 0); // 0

Parameters

• callback: () -> dyn! - A function that returns a default value

Returns

dyn! - The success value or the result of calling the callback