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+/*
+ * Copyright © 2013 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authored by: Thomas Voß <thomas.voss@canonical.com>
+ */
+#ifndef CORE_PROPERTY_H_
+#define CORE_PROPERTY_H_
+
+#include <core/signal.h>
+
+#include <iostream>
+
+namespace core
+{
+/**
+ * @brief A very simple, templated class that allows for uniform declaration of get-able/set-able/observable members.
+ * @tparam The type of the value contained within the property.
+ */
+template<typename T>
+class Property
+{
+ public:
+ /**
+ * @brief ValueType refers to the type of the contained value.
+ */
+ typedef T ValueType;
+
+ /**
+ * @brief Property creates a new instance of property and initializes the contained value.
+ * @param t The initial value, defaults to Property<T>::default_value().
+ */
+ inline explicit Property(const T& t = T{}) : value{t}
+ {
+ }
+
+ /**
+ * @brief Copy c'tor, only copies the contained value, not the changed signal and its connections.
+ * @param rhs
+ */
+ inline Property(const Property<T>& rhs) : value{rhs.value}
+ {
+ }
+
+ inline virtual ~Property() = default;
+
+ /**
+ * @brief Assignment operator, only assigns to the contained value.
+ * @param rhs The right-hand-side, raw value to assign to this property.
+ */
+ inline Property& operator=(const T& rhs)
+ {
+ set(rhs);
+ return *this;
+ }
+
+ /**
+ * @brief Assignment operator, only assigns to the contained value, not the changed signal and its connections.
+ * @param rhs The right-hand-side property to assign from.
+ */
+ inline Property& operator=(const Property<T>& rhs)
+ {
+ set(rhs.value);
+ return *this;
+ }
+
+ /**
+ * @brief Explicit casting operator to the contained value type.
+ * @return A non-mutable reference to the contained value.
+ */
+ inline operator const T&() const
+ {
+ return get();
+ }
+
+ /**
+ * @brief Provides access to a pointer to the contained value.
+ */
+ inline const T* operator->() const
+ {
+ return &get();
+ }
+
+ /**
+ * @brief operator == checks if the value of a property and a raw value are equal.
+ * @param lhs Non-mutable reference to a property.
+ * @param rhs Non-mutable reference to a raw value.
+ * @return True iff the value contained in lhs equals rhs.
+ */
+ friend inline bool operator==(const Property<T>& lhs, const T& rhs)
+ {
+ return lhs.get() == rhs;
+ }
+
+ /**
+ * @brief operator == checks if the value of two properties are equal.
+ * @param lhs Non-mutable reference to a property.
+ * @param rhs Non-mutable reference to a property.
+ * @return True iff the value contained in lhs equals the value contained in rhs.
+ */
+ friend inline bool operator==(const Property<T>& lhs, const Property<T>& rhs)
+ {
+ return lhs.get() == rhs.get();
+ }
+
+ /**
+ * @brief Set the contained value to the provided value. Notify observers of the change.
+ * @param [in] new_value The new value to assign to this property.
+ * @post get() == new_value;
+ */
+ inline virtual void set(const T& new_value)
+ {
+ if (value != new_value)
+ {
+ value = new_value;
+ signal_changed(value);
+ }
+ }
+
+ /**
+ * @brief Access the value contained within this property.
+ * @return A non-mutable reference to the property value.
+ */
+ inline virtual const T& get() const
+ {
+ return value;
+ }
+
+ /**
+ * @brief Access to the changed signal, allows observers to subscribe to change notifications.
+ * @return A non-mutable reference to the changed signal.
+ */
+ inline const Signal<T>& changed() const
+ {
+ return signal_changed;
+ }
+
+ /**
+ * @brief Provides in-place update facilities.
+ *
+ * The provided update_functor is applied to the contained value. If the update functor
+ * returns true, indicating that the value has been changed, the changed signal is emitted.
+ *
+ * @param update_functor The update function to be applied to the contained value.
+ * @return true iff application of the update functor has been successful.
+ */
+ inline virtual bool update(const std::function<bool(T& t)>& update_functor)
+ {
+ if (update_functor(mutable_get()))
+ {
+ signal_changed(value);
+ return true;
+ }
+
+ return false;
+ }
+
+ protected:
+ inline T& mutable_get() const
+ {
+ return value;
+ }
+
+ private:
+ mutable T value;
+ Signal<T> signal_changed;
+};
+}
+
+#endif // CORE_PROPERTY_H_