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Tidy up lazy implementation.

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This commit is contained in:
John Maguire 2016-02-11 14:09:36 +00:00
parent 4c8b1d8143
commit a7ca007e24
1 changed files with 37 additions and 7 deletions
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44
ext/libclementine-common/core/lazy.h
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@ -1,25 +1,55 @@
/* This file is part of Clementine.
Copyright 2016, John Maguire <john.maguire@gmail.com>
Clementine is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Clementine 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with Clementine. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef LAZY_H
#define LAZY_H
#include <functional>
#include <memory>
// Helper for lazy initialisation of objects.
// Usage:
// Lazy<Foo> my_lazy_object([]() { return new Foo; });
template <typename T>
class Lazy {
public:
explicit Lazy(std::function<T*()> init) : init_(init) {}
T* get() {
if (!ptr_) {
ptr_.reset(init_());
}
T* get() const {
CheckInitialised();
return ptr_.get();
}
typename std::add_lvalue_reference<T>::type operator*() const {
CheckInitialised();
return *ptr_;
}
T* operator->() const { return ptr_.get(); }
T* operator->() const { return get(); }
private:
std::function<T*()> init_;
std::unique_ptr<T> ptr_;
void CheckInitialised() const {
if (!ptr_) {
ptr_.reset(init_());
}
}
const std::function<T*()> init_;
mutable std::unique_ptr<T> ptr_;
};
#endif // LAZY_H