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OptionError

Overview​

The OptionError class is a specialized error type in the @ts-rust/std library, used specifically with the Option type to indicate errors related to optional value operations. It extends the AnyError class where template T is OptionErrorKind and provides additional context about why an Option operation failed.

When It Appears​

OptionError is thrown in scenarios involving the Option type, such as attempting to unwrap a None value using methods like unwrap() or expect().

Usage​

OptionError is encountered when working with the Option type and its methods. It helps developers identify and handle cases where an expected value is absent (None).

Example​

import { none, Option, isOptionError } from "@ts-rust/std";

// Create an Option with no value
const maybeValue: Option<number> = none();

try {
  // Attempt to unwrap a None value, which throws an OptionError
  const value = maybeValue.unwrap();
} catch (e) {
  if (isOptionError(e)) {
    console.log(e.message); // "[UnwrapCalledOnNone] `unwrap`: called on `None`."
  }
}

// Using expect() with a custom message
try {
  maybeValue.expect("Expected a number, but got None");
} catch (e) {
  if (isOptionError(e)) {
    console.log(e.message); // "[ExpectCalledOnNone] Expected a number, but got None."
  }
}

OptionErrorKind Values​

The OptionError class uses the OptionErrorKind enum to categorize errors. Each value corresponds to a specific failure scenario:

KindDescription
ValueAccessedOnNoneThrown when the value property is accessed on a None variant.
ExpectCalledOnNoneThrown when expect() is called on a None variant.
UnwrapCalledOnNoneThrown when unwrap() is called on a None variant.
PredicateExceptionThrown when a callback/predicate passed to a method throws an exception (e.g., map, filter, unwrapOrElse, mapOrElse, match, getOrInsertWith).

See Also​