| // Copyright 2022 The Chromium 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 CHROME_BROWSER_UI_BROWSER_USER_DATA_H_ |
| #define CHROME_BROWSER_UI_BROWSER_USER_DATA_H_ |
| |
| #include "base/check.h" |
| #include "base/memory/ptr_util.h" |
| #include "base/memory/raw_ptr.h" |
| #include "base/supports_user_data.h" |
| #include "chrome/browser/ui/browser.h" |
| |
| // A base class for classes attached to, and scoped to, the lifetime of a |
| // Browser. For example: |
| // |
| // --- in foo_helper.h --- |
| // class FooHelper : public BrowserUserData<FooHelper> { |
| // public: |
| // ~FooHelper() override; |
| // |
| // // ... more public stuff here ... |
| // |
| // private: |
| // explicit FooHelper(Browser* browser); |
| // |
| // friend BrowserUserData; |
| // BROWSER_USER_DATA_KEY_DECL(); |
| // |
| // // ... more private stuff here ... |
| // }; |
| // |
| // --- in foo_helper.cc --- |
| // BROWSER_USER_DATA_KEY_IMPL(FooHelper) |
| |
| template <typename T> |
| class BrowserUserData : public base::SupportsUserData::Data { |
| public: |
| explicit BrowserUserData(Browser& browser) : browser_(&browser) {} |
| |
| // Creates an object of type T, and attaches it to the specified Browser. |
| // If an instance is already attached, does nothing. |
| template <typename... Args> |
| static void CreateForBrowser(Browser* browser, Args&&... args) { |
| DCHECK(browser); |
| if (!FromBrowser(browser)) { |
| browser->SetUserData( |
| UserDataKey(), |
| base::WrapUnique(new T(browser, std::forward<Args>(args)...))); |
| } |
| } |
| |
| // Retrieves the instance of type T that was attached to the specified |
| // Browser (via CreateForBrowser above) and returns it. If no instance |
| // of the type was attached, returns nullptr. |
| static T* FromBrowser(Browser* browser) { |
| DCHECK(browser); |
| return static_cast<T*>(browser->GetUserData(UserDataKey())); |
| } |
| static const T* FromBrowser(const Browser* browser) { |
| DCHECK(browser); |
| return static_cast<const T*>(browser->GetUserData(UserDataKey())); |
| } |
| |
| static T* GetOrCreateForBrowser(Browser* browser) { |
| if (auto* data = FromBrowser(browser)) { |
| return data; |
| } |
| |
| CreateForBrowser(browser); |
| return FromBrowser(browser); |
| } |
| |
| // Removes the instance attached to the specified Browser. |
| static void RemoveFromBrowser(Browser* browser) { |
| DCHECK(FromBrowser(browser)); |
| browser->RemoveUserData(UserDataKey()); |
| } |
| |
| static const void* UserDataKey() { return &T::kUserDataKey; } |
| |
| // Returns the Browser associated with `this` object of a subclass |
| // which inherits from BrowserUserData. |
| // |
| // The returned `Browser` is guaranteed to live as long as `this` |
| // BrowserUserData (due to how UserData works - Browser |
| // owns `this` UserData). |
| Browser& GetBrowser() { return *browser_; } |
| const Browser& GetBrowser() const { return *browser_; } |
| |
| private: |
| // Browser associated with subclass which inherits this BrowserUserData. |
| const raw_ptr<Browser> browser_ = nullptr; |
| }; |
| |
| // Users won't be able to instantiate the template if they miss declaring the |
| // user data key. |
| // This macro declares a static variable inside the class that inherits from |
| // BrowserUserData. The address of this static variable is used as |
| // the key to store/retrieve an instance of the class. |
| #define BROWSER_USER_DATA_KEY_DECL() static const int kUserDataKey = 0 |
| |
| // This macro instantiates the static variable declared by the previous macro. |
| // It must live in a .cc file to ensure that there is only one instantiation |
| // of the static variable. |
| #define BROWSER_USER_DATA_KEY_IMPL(Type) const int Type::kUserDataKey |
| |
| #endif // CHROME_BROWSER_UI_BROWSER_USER_DATA_H_ |