Represents a one-to-one relationship through a join table. More...

#include <HasOneThrough.hpp>

Classes
struct	Loader
	Carries the deferred load, installed by the DataMapper. More...

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

using	ReferencedRecord = OtherTable
	The record type of the "Other" side of the relationship.

Public Member Functions
LIGHTWEIGHT_FORCE_INLINE constexpr void	EmplaceRecord (std::shared_ptr< ReferencedRecord > record)
	Emplaces the given record into this relationship.

LIGHTWEIGHT_FORCE_INLINE RelationResult< std::reference_wrapper< ReferencedRecord > >	Record ()
	Retrieves the record in this relationship, loading it on first access.

LIGHTWEIGHT_FORCE_INLINE RelationResult< std::reference_wrapper< ReferencedRecord const > >	Record () const
	Retrieves the record in this relationship, loading it on first access.

LIGHTWEIGHT_FORCE_INLINE constexpr bool	IsLoaded () const noexcept
	Checks if the record is loaded.

LIGHTWEIGHT_FORCE_INLINE void	Unload () noexcept
	Unloads the record from memory, so the next access loads it again.

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord &	operator* ()
	Retrieves the record in this relationship, loading it on first access.

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord const &	operator* () const
	Retrieves the record in this relationship, loading it on first access.

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord *	operator-> ()
	Retrieves the record in this relationship, loading it on first access.

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord const *	operator-> () const
	Retrieves the record in this relationship, loading it on first access.

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

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

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	ThroughSelector = TheThroughSelector
	Singles out ReferencedRecord's foreign key pointing at ThroughRecord.

Detailed Description

template<typename OtherTable, typename ThroughSpec, auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>
class Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >

Represents a one-to-one relationship through a join table.

The OtherTable parameter is the record reached through the join table. The ThroughSpec parameter is the join table, which references the current record. It is named with the Through marker, so that the reader can tell it apart from the referenced record:

struct Account;
struct AccountHistory;
struct Supplier
{
    Field<int, PrimaryKey::AutoAssign> id;
    HasOneThrough<AccountHistory, Through<Account>> accountHistory;
};

Both foreign keys are located by matching the relationship type. When either record holds more than one foreign key into the same table, name the column to single one out - see the RelationSelector concept and the example on HasManyThrough.

Template Parameters

OtherTable	The record type reached through the join table.
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.
TheThroughSelector	Singles out `OtherTable's` foreign key pointing at the join record.

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

Definition at line 50 of file HasOneThrough.hpp.

Member Typedef Documentation

◆ ThroughRecord

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

using Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::ThroughRecord = ThroughRecordOf<ThroughSpec>

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

Definition at line 62 of file HasOneThrough.hpp.

◆ ReferencedRecord

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

using Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::ReferencedRecord = OtherTable

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

Definition at line 65 of file HasOneThrough.hpp.

Member Function Documentation

◆ EmplaceRecord()

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE constexpr void Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::EmplaceRecord ( std::shared_ptr< ReferencedRecord > record )

inlineconstexpr

Emplaces the given record into this relationship.

Definition at line 74 of file HasOneThrough.hpp.

◆ Record() [1/2]

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE RelationResult< std::reference_wrapper< ReferencedRecord > > Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::Record ( )

inline

Retrieves the record in this relationship, loading it on first access.

Never throws for an unavailable record: the reason comes back as the error instead.

Returns: The record; or RelationError::NotFound when there is none, RelationError::NotConfigured when there is no loader (a hand-built record, or one read with loadRelations = false), RelationError::Outdated when the default connection string changed since the record was read, RelationError::QueryFailed when the load query failed.

Definition at line 89 of file HasOneThrough.hpp.

◆ Record() [2/2]

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE RelationResult< std::reference_wrapper< ReferencedRecord const > > Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::Record ( ) const

inline

Retrieves the record in this relationship, loading it on first access.

Never throws for an unavailable record: the reason comes back as the error instead.

Returns: The record; or RelationError::NotFound when there is none, RelationError::NotConfigured when there is no loader (a hand-built record, or one read with loadRelations = false), RelationError::Outdated when the default connection string changed since the record was read, RelationError::QueryFailed when the load query failed.

Definition at line 95 of file HasOneThrough.hpp.

◆ IsLoaded()

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE constexpr bool Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::IsLoaded ( ) const

inlineconstexprnoexcept

Checks if the record is loaded.

Definition at line 101 of file HasOneThrough.hpp.

◆ Unload()

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE void Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::Unload ( )

inlinenoexcept

Unloads the record from memory, so the next access loads it again.

Definition at line 107 of file HasOneThrough.hpp.

◆ operator*() [1/2]

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord & Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::operator* ( )

inline

Retrieves the record in this relationship, loading it on first access.

Exceptions

SqlRequireLoadedError The record is unavailable; Record() reports why without throwing.

Definition at line 115 of file HasOneThrough.hpp.

◆ operator*() [2/2]

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord const & Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::operator* ( ) const

inline

Retrieves the record in this relationship, loading it on first access.

Exceptions

SqlRequireLoadedError The record is unavailable; Record() reports why without throwing.

Definition at line 122 of file HasOneThrough.hpp.

◆ operator->() [1/2]

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord * Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::operator-> ( )

inline

Retrieves the record in this relationship, loading it on first access.

Exceptions

SqlRequireLoadedError The record is unavailable; Record() reports why without throwing.

Definition at line 130 of file HasOneThrough.hpp.

◆ operator->() [2/2]

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

LIGHTWEIGHT_FORCE_INLINE ReferencedRecord const * Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::operator-> ( ) const

inline

Retrieves the record in this relationship, loading it on first access.

Exceptions

SqlRequireLoadedError The record is unavailable; Record() reports why without throwing.

Definition at line 137 of file HasOneThrough.hpp.

◆ SetAutoLoader()

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

void Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::SetAutoLoader ( Loader loader )

inline

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

Definition at line 154 of file HasOneThrough.hpp.

Member Data Documentation

◆ OwnerSelector

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

constexpr auto Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::OwnerSelector = TheOwnerSelector

staticconstexpr

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

Definition at line 68 of file HasOneThrough.hpp.

◆ ThroughSelector

template<typename OtherTable , typename ThroughSpec , auto TheOwnerSelector = AutoDetectRelation, auto TheThroughSelector = AutoDetectRelation>

constexpr auto Lightweight::HasOneThrough< OtherTable, ThroughSpec, TheOwnerSelector, TheThroughSelector >::ThroughSelector = TheThroughSelector

staticconstexpr

Singles out ReferencedRecord's foreign key pointing at ThroughRecord.

Definition at line 71 of file HasOneThrough.hpp.

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

Lightweight/DataMapper/HasOneThrough.hpp

Classes

Public Types

Public Member Functions

Static Public Attributes

Detailed Description

Member Typedef Documentation

◆ ThroughRecord

◆ ReferencedRecord

Member Function Documentation

◆ EmplaceRecord()

◆ Record() [1/2]

◆ Record() [2/2]

◆ IsLoaded()

◆ Unload()

◆ operator*() [1/2]

◆ operator*() [2/2]

◆ operator->() [1/2]

◆ operator->() [2/2]

◆ SetAutoLoader()

Member Data Documentation

◆ OwnerSelector

◆ ThroughSelector