This API represents a many-to-many relationship between two records through a third record. More...

#include <HasManyThrough.hpp>

Public Types
using	ThroughRecord = ThroughRecordOf< ThroughSpec >
	The record type of the "through" side of the relationship.

using	ReferencedRecord = ReferencedRecordT
	The record type of the "many" side of the relationship.

using	ReferencedRecordList = std::vector< std::shared_ptr< ReferencedRecord > >
	The list of records on the "many" side of the relationship.

using	value_type = ReferencedRecord
	Value type for range-based iteration.

using	iterator = ReferencedRecordList::iterator
	Iterator type for the list of records.

using	const_iterator = ReferencedRecordList::const_iterator
	Const iterator type for the list of records.

Public Member Functions
ReferencedRecordList const &	All () const noexcept
	Retrieves the list of loaded records.

ReferencedRecordList &	All () noexcept
	Retrieves the list of records as mutable reference.

ReferencedRecordList &	Emplace (ReferencedRecordList &&records) noexcept
	Emplaces the given list of records into this relationship.

std::size_t	Count () const
	Retrieves the number of records in this relationship.

bool	IsEmpty () const
	Checks if this relationship is empty.

ReferencedRecord const &	At (std::size_t index) const
	Retrieves the record at the given index.

ReferencedRecord &	At (std::size_t index)
	Retrieves the record at the given index.

ReferencedRecord const &	operator[] (std::size_t index) const
	Retrieves the record at the given index.

ReferencedRecord &	operator[] (std::size_t index)
	Retrieves the record at the given index.

iterator	begin () noexcept
	Returns an iterator to the beginning of the record list.

iterator	end () noexcept
	Returns an iterator to the end of the record list.

const_iterator	begin () const noexcept
	Returns a const iterator to the beginning of the record list.

const_iterator	end () const noexcept
	Returns a const iterator to the end of the record list.

std::weak_ordering	operator<=> (HasManyThrough const &other) const noexcept=default
	Default three-way comparison operator.

void	SetAutoLoader (Loader loader) noexcept
	Used internally to configure on-demand loading of the records.

void	Reload ()
	Reloads the records from the database.

template<typename Callable >
void	Each (Callable const &callable)
	Iterates over all records in this relationship.

Static Public Attributes
static constexpr auto	OwnerSelector = TheOwnerSelector
	Singles out the join record's foreign key pointing at the record owning this relationship.

static constexpr auto	ReferencedSelector = TheReferencedSelector
	Singles out the join record's foreign key pointing at ReferencedRecord.

Detailed Description

template<typename ReferencedRecordT, typename ThroughSpec, auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>
class Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >

This API represents a many-to-many relationship between two records through a third record.

The join record is named with the Through marker, so that the reader can tell it apart from the referenced record at a glance:

struct Friendship;
struct Human
{
    Field<int, PrimaryKey::AutoAssign> id;
    HasManyThrough<Human, Through<Friendship>> friends;
};

The join record must declare one BelongsTo pointing back at the record owning this relationship, and one pointing at the referenced record. Both are located by matching the relationship type.

When the join record cannot be resolved that way - most notably a self-referential many-to-many, where both of its foreign keys point at the same table - name the two foreign key columns explicitly:

struct Friendship;
struct Human
{
    Field<int, PrimaryKey::AutoAssign> id;
    HasManyThrough<Human, Through<Friendship>, SqlRealName { "a_id" }, SqlRealName { "b_id" }> friends;
};
struct Friendship
{
    Field<int, PrimaryKey::AutoAssign> id;
    BelongsTo<&Human::id, SqlRealName { "a_id" }> a;
    BelongsTo<&Human::id, SqlRealName { "b_id" }> b;
};

Template Parameters

ReferencedRecordT	The record type on the "many" side of the relationship.
ThroughSpec	The join record, wrapped as `Through<T>`. Naming the record bare is deprecated.
TheOwnerSelector	Singles out the join record's foreign key pointing at the owning record.
TheReferencedSelector	Singles out the join record's foreign key pointing at `ReferencedRecordT`.

See also: DataMapper, Field, HasMany, Through, RelationSelector

Definition at line 66 of file HasManyThrough.hpp.

Member Typedef Documentation

◆ ThroughRecord

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

using Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::ThroughRecord = ThroughRecordOf<ThroughSpec>

The record type of the "through" side of the relationship.

Definition at line 78 of file HasManyThrough.hpp.

◆ ReferencedRecord

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

using Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::ReferencedRecord = ReferencedRecordT

The record type of the "many" side of the relationship.

Definition at line 81 of file HasManyThrough.hpp.

◆ ReferencedRecordList

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

using Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::ReferencedRecordList = std::vector<std::shared_ptr<ReferencedRecord> >

The list of records on the "many" side of the relationship.

Definition at line 90 of file HasManyThrough.hpp.

◆ value_type

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

using Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::value_type = ReferencedRecord

Value type for range-based iteration.

Definition at line 93 of file HasManyThrough.hpp.

◆ iterator

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

using Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::iterator = ReferencedRecordList::iterator

Iterator type for the list of records.

Definition at line 95 of file HasManyThrough.hpp.

◆ const_iterator

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

using Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::const_iterator = ReferencedRecordList::const_iterator

Const iterator type for the list of records.

Definition at line 97 of file HasManyThrough.hpp.

Member Function Documentation

◆ All() [1/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecordList const & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::All ( ) const

noexcept

Retrieves the list of loaded records.

Definition at line 232 of file HasManyThrough.hpp.

Referenced by Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::Each().

◆ All() [2/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecordList & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::All ( )

noexcept

Retrieves the list of records as mutable reference.

Definition at line 241 of file HasManyThrough.hpp.

◆ Emplace()

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecordList & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::Emplace ( ReferencedRecordList && records )

noexcept

Emplaces the given list of records into this relationship.

Definition at line 253 of file HasManyThrough.hpp.

◆ Count()

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

std::size_t Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::Count ( ) const

Retrieves the number of records in this relationship.

Definition at line 261 of file HasManyThrough.hpp.

◆ IsEmpty()

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

bool Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::IsEmpty ( ) const

Checks if this relationship is empty.

Definition at line 274 of file HasManyThrough.hpp.

References Count.

◆ At() [1/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecord const & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::At ( std::size_t index ) const

Retrieves the record at the given index.

Parameters

index The index of the record to retrieve.

Note: This method will on-demand load the records if they are not already loaded.; This method will throw if the index is out of bounds.

Definition at line 281 of file HasManyThrough.hpp.

◆ At() [2/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecord & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::At ( std::size_t index )

Retrieves the record at the given index.

Parameters

index The index of the record to retrieve.

Note: This method will on-demand load the records if they are not already loaded.; This method will throw if the index is out of bounds.

Definition at line 288 of file HasManyThrough.hpp.

◆ operator[]() [1/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecord const & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::operator[] ( std::size_t index ) const

Retrieves the record at the given index.

Parameters

index The index of the record to retrieve.

Note: This method will on-demand load the records if they are not already loaded.; This method will NOT throw if the index is out of bounds. The behaviour is undefined.

Definition at line 295 of file HasManyThrough.hpp.

◆ operator[]() [2/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::ReferencedRecord & Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::operator[] ( std::size_t index )

Retrieves the record at the given index.

Parameters

index The index of the record to retrieve.

Note: This method will on-demand load the records if they are not already loaded.; This method will NOT throw if the index is out of bounds. The behaviour is undefined.

Definition at line 302 of file HasManyThrough.hpp.

◆ begin() [1/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::iterator Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::begin ( )

noexcept

Returns an iterator to the beginning of the record list.

Definition at line 309 of file HasManyThrough.hpp.

◆ end() [1/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::iterator Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::end ( )

noexcept

Returns an iterator to the end of the record list.

Definition at line 316 of file HasManyThrough.hpp.

◆ begin() [2/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::const_iterator Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::begin ( ) const

noexcept

Returns a const iterator to the beginning of the record list.

Definition at line 323 of file HasManyThrough.hpp.

◆ end() [2/2]

template<typename ReferencedRecordT , typename ThroughSpec , auto OwnerSelector, auto ReferencedSelector>

HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::const_iterator Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, OwnerSelector, ReferencedSelector >::end ( ) const

noexcept

Returns a const iterator to the end of the record list.

Definition at line 330 of file HasManyThrough.hpp.

◆ SetAutoLoader()

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

void Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::SetAutoLoader ( Loader loader )

inlinenoexcept

Used internally to configure on-demand loading of the records.

Definition at line 162 of file HasManyThrough.hpp.

◆ Reload()

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

void Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::Reload ( )

inline

Reloads the records from the database.

Definition at line 168 of file HasManyThrough.hpp.

◆ Each()

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

template<typename Callable >

void Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::Each ( Callable const & callable )

inline

Iterates over all records in this relationship.

Parameters

callable The callable to invoke for each record.

Note: This method will on-demand load the records if they are not already loaded, but not hold them all in memory.

Definition at line 181 of file HasManyThrough.hpp.

References Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::All().

Member Data Documentation

◆ OwnerSelector

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

constexpr auto Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::OwnerSelector = TheOwnerSelector

staticconstexpr

Singles out the join record's foreign key pointing at the record owning this relationship.

Definition at line 84 of file HasManyThrough.hpp.

◆ ReferencedSelector

template<typename ReferencedRecordT , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheReferencedSelector = AutoDetectRelation>

constexpr auto Lightweight::HasManyThrough< ReferencedRecordT, ThroughSpec, TheOwnerSelector, TheReferencedSelector >::ReferencedSelector = TheReferencedSelector

staticconstexpr

Singles out the join record's foreign key pointing at ReferencedRecord.

Definition at line 87 of file HasManyThrough.hpp.

The documentation for this class was generated from the following file:

Lightweight/DataMapper/HasManyThrough.hpp

Public Types

Public Member Functions

Static Public Attributes

Detailed Description

Member Typedef Documentation

◆ ThroughRecord

◆ ReferencedRecord

◆ ReferencedRecordList

◆ value_type

◆ iterator

◆ const_iterator

Member Function Documentation

◆ All() [1/2]

◆ All() [2/2]

◆ Emplace()

◆ Count()

◆ IsEmpty()

◆ At() [1/2]

◆ At() [2/2]

◆ operator[]() [1/2]

◆ operator[]() [2/2]

◆ begin() [1/2]

◆ end() [1/2]

◆ begin() [2/2]

◆ end() [2/2]

◆ SetAutoLoader()

◆ Reload()

◆ Each()

Member Data Documentation

◆ OwnerSelector

◆ ReferencedSelector