Struct HasOne

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

A non-optional “has one” association.

Imagine you have these models:

struct User {
    id: i32,
    country_id: i32,
}

struct Country {
    id: i32,
}

For this setup we say “a user has one country”. This means that User has a field named country_id that references the id of another country.

Example

You can find a complete example of HasOne here.

Attributes

Name	Description	Default	Example
foreign_key_field	The name of the foreign key field	{name of field}_id	foreign_key_field = country_id
root_model_field	The name of the field on the associated GraphQL type that holds the model	{name of field}	root_model_field = country
graphql_field	The name of this field in your GraphQL schema	{name of field}	graphql_field = country
child_primary_key_field	The name of the primary key field on the associated model	id	child_primary_key_field = identifier
default	Use the default value for all unspecified attributes	N/A	default

Additionally it also supports the attributes print, skip, and field_arguments. See the root model docs for more into on those.

Errors

When calling try_unwrap to get the loaded value it will return an error if the value has not been loaded, or if the load failed.

For example if a user has a country_id of 10 but there is no Country with id 10 then try_unwrap will return an error.

Implementations

impl<T> HasOne<T>

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

Borrow the loaded value. If the value has not been loaded it will return an error.

Trait Implementations

impl<T> Association<T> for HasOne<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 HasOne<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 HasOne<T>

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

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for HasOne<T>

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

Formats the value using the given formatter.

impl<T> Default for HasOne<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: Ord> Ord for HasOne<T>

fn cmp(&self, other: &HasOne<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 HasOne<T>

fn eq(&self, other: &HasOne<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 HasOne<T>

fn partial_cmp(&self, other: &HasOne<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 HasOne<T>

impl<T> StructuralPartialEq for HasOne<T>