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In some cases you want to store property data for each instance. Often you'll use member data on the entities themselves for this. But in some cases you don't want to bloat the entity class with data for seldomly used properties. In these cases you can instead use the PropertyInstanceState class, and keep a static instance of this per property.
101 lines
3.4 KiB
C++
101 lines
3.4 KiB
C++
/*
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Copyright (C) 2015 Erik Ogenvik
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef RULESETS_PROPERTYINSTANCESTATE_H_
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#define RULESETS_PROPERTYINSTANCESTATE_H_
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#include <unordered_map>
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#include <cassert>
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class LocatedEntity;
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/**
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* @brief Handles entity specific property state.
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*
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* In some cases you want to save instance state per entity. Often in those cases you can store
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* it in some member directly on the entity. But sometimes you don't want to bloat the entity with
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* fields for seldom used properties. In those cases this class becomes useful.
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* An instance is meant to be used as a static field of the property. When the property is installed
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* on the entity addState should be called, and when it's removed removeState must be called.
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* Failing to call removeState properly will lead to an assert error on shutdown.
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*/
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template <typename T>
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class PropertyInstanceState {
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private:
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std::unordered_map<const LocatedEntity*, T*> mStates;
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public:
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~PropertyInstanceState() {
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//When an instance of this is destroyed, all entities should already have deregistered themselves from it.
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assert(mStates.empty());
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}
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/**
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* Adds a new state for the specified entity.
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* @param entity An entity.
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* @param state A new state instance.
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*/
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void addState(const LocatedEntity* entity, T* state) {
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mStates.insert(std::make_pair(entity, state));
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}
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/**
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* Gets the state for the supplied entity.
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* @param entity An entity.
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* @return The registered state, or null.
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*/
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T* getState(const LocatedEntity* entity) const {
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auto I = mStates.find(entity);
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if (I != mStates.end()) {
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return I->second;
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}
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return nullptr;
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}
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/**
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* Removes the state for the supplied entity.
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*
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* Calling this will delete the state instance.
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* @param entity An entity.
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*/
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void removeState(const LocatedEntity* entity) {
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auto I = mStates.find(entity);
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if (I != mStates.end()) {
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delete I->second;
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mStates.erase(I);
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}
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}
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/**
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* Replaces the existing state registered for the entity with a new state.
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*
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* The existing state instance will be deleted.
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* @param entity An entity.
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* @param state A new state.
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*/
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void replaceState(const LocatedEntity* entity, T* state) {
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auto I = mStates.find(entity);
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if (I != mStates.end()) {
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delete I->second;
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I->second = state;
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}
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}
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};
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#endif /* RULESETS_PROPERTYINSTANCESTATE_H_ */
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