Struct OptionHasOne

pub struct OptionHasOne<T>(/* private fields */);

An optional “has-one association”.

It works exactly like HasOne except it doesn’t error if the association doesn’t get loaded. The value doesn’t get loaded it defaults to None.

Example

You can find a complete example of OptionHasMany here.

Attributes

It supports the same attributes as HasOne.

Errors

try_unwrap will never error. If the association wasn’t loaded or wasn’t found it will return Ok(None).

Implementations

impl<T> OptionHasOne<T>

pub fn try_unwrap(&self) -> Result<&Option<T>, Error>

Borrow the loaded value. If the value has not been loaded it will return Ok(None). It will not error.

Trait Implementations

impl<T> Association<T> for OptionHasOne<Box<T>>

fn loaded_child(&mut self, child: T)

Store the loaded child on the association.

fn assert_loaded_otherwise_failed(&mut self)

The association should have been loaded by now, if not store an error inside the association (if applicable for the particular association).

impl<T> Association<T> for OptionHasOne<T>

fn loaded_child(&mut self, child: T)

Store the loaded child on the association.

fn assert_loaded_otherwise_failed(&mut self)

The association should have been loaded by now, if not store an error inside the association (if applicable for the particular association).

impl<T: Clone> Clone for OptionHasOne<T>

fn clone(&self) -> OptionHasOne<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for OptionHasOne<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for OptionHasOne<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: Ord> Ord for OptionHasOne<T>

fn cmp(&self, other: &OptionHasOne<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T: PartialEq> PartialEq for OptionHasOne<T>

fn eq(&self, other: &OptionHasOne<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: PartialOrd> PartialOrd for OptionHasOne<T>

fn partial_cmp(&self, other: &OptionHasOne<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: Eq> Eq for OptionHasOne<T>

impl<T> StructuralPartialEq for OptionHasOne<T>