| // Copyright (c) 2014 The Chromium OS Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef SHILL_PROPERTY_OBSERVER_H_ |
| #define SHILL_PROPERTY_OBSERVER_H_ |
| |
| #include <base/basictypes.h> |
| #include <base/callback.h> |
| #include <memory> |
| |
| #include "shill/accessor_interface.h" |
| #include "shill/error.h" |
| #include "shill/property_observer_interface.h" |
| |
| namespace shill { |
| |
| // A templated object that retains a reference to a typed accessor, |
| // and a saved value retrieved from the accessor. When the update |
| // method is called, it compares its saved value to the current |
| // value returned by the accessor. If the value has changed, it |
| // calls the supplied callback and updates the saved value. |
| template <class T> |
| class PropertyObserver : public PropertyObserverInterface { |
| public: |
| typedef base::Callback<void(const T &new_value)> Callback; |
| |
| PropertyObserver(std::shared_ptr<AccessorInterface<T>> accessor, |
| Callback callback) |
| : accessor_(accessor), callback_(callback) { |
| Error unused_error; |
| saved_value_ = accessor_->Get(&unused_error); |
| } |
| virtual ~PropertyObserver() {} |
| |
| // Implements PropertyObserverInterface. Compares the saved value with |
| // what the Get() method of |accessor_| returns. If the value has changed |
| // |callback_| is invoked and |saved_value_| is updated. |
| virtual void Update() override { |
| Error error; |
| T new_value_ = accessor_->Get(&error); |
| if (!error.IsSuccess() || saved_value_ == new_value_) { |
| return; |
| } |
| callback_.Run(new_value_); |
| saved_value_ = new_value_; |
| } |
| |
| private: |
| friend class PropertyObserverTest; |
| |
| std::shared_ptr<AccessorInterface<T>> accessor_; |
| Callback callback_; |
| T saved_value_; |
| |
| DISALLOW_COPY_AND_ASSIGN(PropertyObserver); |
| }; |
| |
| } // namespace shill |
| |
| #endif // SHILL_PROPERTY_OBSERVER_H_ |