Class NoneImpl

Calls mapper if the Option is Some, otherwise returns None. This function can be used for control flow based on Option values.

Returns the contained Some value, if exists. Throws an error if not.

If you know you're dealing with Some and the compiler knows it too (because you tested isSome() or isNone()) you should use value instead. While Some's expect() and value will both return the same value using value is preferable because it makes it clear that there won't be an exception thrown on access.

true when the Option is None

true when the Option is Some

Maps an Option<T> to Option<U> by applying a function to a contained Some value, leaving a None value untouched.

This function can be used to compose the Options of two functions.

Maps an Option<T> to Option<U> by either converting T to U using mapper (in case of Some) or using the default_ value (in case of None).

If default is a result of a function call consider using mapOrElse() instead, it will only evaluate the function when needed.

Maps an Option<T> to Option<U> by either converting T to U using mapper (in case of Some) or producing a default value using the default function (in case of None).

Returns Some() if we have a value, otherwise returns other.

other is evaluated eagerly. If other is a result of a function call try orElse() instead – it evaluates the parameter lazily.

Example

Some(1).or(Some(2)) // => Some(1)
None.or(Some(2)) // => Some(2)
Copy

Returns Some() if we have a value, otherwise returns the result of calling other().

other() is called only when needed.

Example

Some(1).orElse(() => Some(2)) // => Some(1)
None.orElse(() => Some(2)) // => Some(2)
Copy

Maps an Option<T> to a Result<T, E>.

Returns the contained Some value. Because this function may throw, its use is generally discouraged. Instead, prefer to handle the None case explicitly.

If you know you're dealing with Some and the compiler knows it too (because you tested isSome() or isNone()) you should use value instead. While Some's unwrap() and value will both return the same value using value is preferable because it makes it clear that there won't be an exception thrown on access.

Throws if the value is None.

Returns the contained Some value or a provided default.

(This is the unwrap_or in rust)