MementoTie< SIG, MEM > Class Template Reference

#include "steam/control/memento-tie.hpp"

Description

template<typename SIG, typename MEM>
class steam::control::MementoTie< SIG, MEM >

Binding together state capturing and execution of the undo operation.

MementoTie itself is a passive container object with a very specific type, depending on the type of the operation arguments and the type of the memento. It is to be allocated within the StorageHolder of the command, thereby wrapping the undo and capture function, setting up the necessary bindings and closures for allowing them to cooperate behind the scenes to carry out the UNDO functionality. On construction, the UndoMutation functor retrieves the wired up functions, storing them into generic containers (type erasure) for later invocation.

More specifically, the captureFunction, which is expected to run immediately prior to the actual command operation, returns a memento value object (of unspecific type), which needs to be stored within the MementoTie. On UNDO, the undo-operation functor needs to be provided with a reference to this stored memento value through an additional parameter (which by convention is always the last argument of the undo function).

Warning

take care of the MementoTie storage location, as the bound functions returned by tieCaptureFunc and tieUndoFunc refer to this implicitly.

Parameters

SIG	signature of the command operation
MEM	type of the memento state to capture. Needs to be default constructible and copyable

Definition at line 79 of file memento-tie.hpp.

Public Member Functions
	MementoTie (function< SIG_undo > const &undoFunc, function< SIG_cap > const &captureFunc)
	creates an execution context tying together the provided functions. More...
void	clear ()
	reverses the effect of capturing state and returns this memento holder into pristine state
MEM &	getState ()
	access the currently captured memento state value More...
bool	isValid () const
	operator bool () const
	conversion to bool() yields true if all functions are usable and memento state has been captured
	operator std::string () const
	for diagnostics: include format-util.hpp
function< SIG >	tieCaptureFunc ()
	bind the capturing function to the internal memento store within this object. More...
function< SIG >	tieUndoFunc ()
	bind the undo function to the internal memento store within this object. More...

Private Types
typedef CommandSignature< SIG, MEM >::CaptureSig	SIG_cap
typedef CommandSignature< SIG, MEM >::UndoOp_Sig	SIG_undo

Private Member Functions
void	capture (MEM const &mementoVal)
	to be chained behind the capture function

Private Attributes
function< SIG_cap >	capture_
bool	isCaptured_
ReplaceableItem< MEM >	memento_
	storage holding the captured state for undo
function< SIG_undo >	undo_

Constructor & Destructor Documentation

MementoTie()

MementoTie ( function< SIG_undo > const &  undoFunc, function< SIG_cap > const &  captureFunc  )

inline

creates an execution context tying together the provided functions.

Bound copies of these functors may be pulled from the MementoTie, in order to build the closures (with the concrete operation arguments) to be invoked later on command execution.

Definition at line 111 of file memento-tie.hpp.

Member Function Documentation

tieUndoFunc()

function<SIG> tieUndoFunc ( )

inline

bind the undo function to the internal memento store within this object.

Returns

a functor, which, when invoked with the remaining arguments, will automatically call getState() to retrieve the current memento value.

Note

similar to getState(), the returned functor will throw when the state capturing wasn't yet invoked

Definition at line 137 of file memento-tie.hpp.

References MementoTie< SIG, MEM >::getState().

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tieCaptureFunc()

function<SIG> tieCaptureFunc ( )

inline

bind the capturing function to the internal memento store within this object.

Returns

a functor, which on invocation will automatically store the return value of the capturing function (= the current memento value) into the field memento_ within this object

Definition at line 152 of file memento-tie.hpp.

References MementoTie< SIG, MEM >::capture().

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getState()

MEM& getState ( )

inline

access the currently captured memento state value

Exceptions

when	the capturing function wasn't yet invoked

Definition at line 164 of file memento-tie.hpp.

Referenced by MementoTie< SIG, MEM >::tieUndoFunc().

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Inheritance diagram for MementoTie< SIG, MEM >:

Collaboration diagram for MementoTie< SIG, MEM >:

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

• memento-tie.hpp