QueryResolver Class Reference

#include "common/query/query-resolver.hpp"

Description

Interface: a facility for resolving (some kind of) queries A concrete subclass has the ability to create Resolution instances in response to specific queries of some kind, if applicable.

Every resolution mechanism is expected to enrol by calling #installResolutionCase. Such a registration is considered permanent; a factory function gets stored, assuming that the entity to implement this function remains available up to the end of Lumiera main(). The kind of query and a suitable resolver is determined by the QueryID, which includes a type-ID. Thus the implementation might downcast query and resultset.

Definition at line 98 of file query-resolver.hpp.

Public Member Functions
bool	canHandle (Goal const &) const
PReso	issue (Goal const &query) const
	issue a query to retrieve contents The query is handed over internally to a suitable resolver implementation. More...
virtual	operator string () const =0
	short characterisation of the actual facility

Protected Types
using	ResolutionMechanism = function< Resolution *(Goal const &)>

Protected Member Functions
virtual bool	canHandleQuery (Goal::QueryID const &) const =0
void	installResolutionCase (Goal::QueryID const &, ResolutionMechanism)

Private Attributes
unique_ptr< QueryDispatcher >	dispatcher_

Additional Inherited Members
Private Member Functions inherited from NonCopyable
	NonCopyable (NonCopyable const &)=delete
NonCopyable &	operator= (NonCopyable const &)=delete

Member Function Documentation

issue()

PReso issue

(

Goal const &

query

)

const

issue a query to retrieve contents The query is handed over internally to a suitable resolver implementation.

Returns

concrete Resolution of the query (ResultSet), managed by smart-pointer.

Exceptions

lumiera::Error

subclass if query evaluation flounders. This might be broken logic, invalid input, misconfiguration or failure of an external facility used for resolution.

Note

a query may yield no results, in which case the iterator is empty.

implementation

For actually building a result set, the QueryResolver base implementation uses an embedded dispatcher table. The concrete query resolving facilities, when implementing the QueryResolver interface, are expected to register individual resolution functions into this QueryDispatcher table. Whenever issuing a Goal, a suitable resolution function is picked based on the Goal::QueryID, which contains an embedded type code. Thus, the individual resolution function can (re)establish a typed context and downcast the Goal appropriately

Definition at line 98 of file query-resolver.cpp.

Inheritance diagram for QueryResolver:

Collaboration diagram for QueryResolver:

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

• query-resolver.hpp
• query-resolver.cpp