Struct HasMany

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

A “has many” association.

Imagine you have these models:

struct User {
    id: i32,
}

struct Car {
    id: i32,
    user_id: i32,
}

For this setup we say “user has many cars” and “cars have one user”. This is the inverse of a HasOne assocation because the foreign key is on Car instead of User.

This means users can own many cars, but cars can only be owned by one user.

Example

You can find a complete example of HasMany here.

Attributes

Name	Description	Default	Example
foreign_key_field	The name of the foreign key field	{name of struct}_id	foreign_key_field = user_id
foreign_key_optional	The foreign key type is optional	Not set	foreign_key_optional
root_model_field	The name of the field on the associated GraphQL type that holds the database model	N/A (unless using skip)	root_model_field = car
graphql_field	The name of this field in your GraphQL schema	{name of field}	graphql_field = country
predicate_method	Method used to filter child associations. This can be used if you only want to include a subset of the models	N/A (attribute is optional)	predicate_method = a_predicate_method

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

Errors

try_unwrap will never error. If the association wasn’t loaded or wasn’t found it will return Ok(vec![]).

Implementations

impl<T> HasMany<T>

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

Borrow the loaded values. If no values have been loaded it will return an empty list. It will not return an error.

Trait Implementations

impl<T> Association<T> for HasMany<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 HasMany<T>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for HasMany<T>

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

Formats the value using the given formatter.

impl<T> Default for HasMany<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: Ord> Ord for HasMany<T>

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

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

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

impl<T> StructuralPartialEq for HasMany<T>