| // Copyright (c) 2012 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 CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_USER_DATA_H_ |
| #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_USER_DATA_H_ |
| |
| #include "base/logging.h" |
| #include "base/supports_user_data.h" |
| #include "content/public/browser/web_contents.h" |
| |
| namespace content { |
| |
| // A base class for classes attached to, and scoped to, the lifetime of a |
| // WebContents. For example: |
| // |
| // --- in foo_tab_helper.h --- |
| // class FooTabHelper : public content::WebContentsUserData<FooTabHelper> { |
| // public: |
| // ~FooTabHelper() override; |
| // // ... more public stuff here ... |
| // private: |
| // explicit FooTabHelper(content::WebContents* contents); |
| // friend class content::WebContentsUserData<FooTabHelper>; |
| // // ... more private stuff here ... |
| // } |
| // --- in foo_tab_helper.cc --- |
| // DEFINE_WEB_CONTENTS_USER_DATA_KEY(FooTabHelper); |
| // |
| template <typename T> |
| class WebContentsUserData : public base::SupportsUserData::Data { |
| public: |
| // Creates an object of type T, and attaches it to the specified WebContents. |
| // If an instance is already attached, does nothing. |
| static void CreateForWebContents(WebContents* contents) { |
| DCHECK(contents); |
| if (!FromWebContents(contents)) |
| contents->SetUserData(UserDataKey(), new T(contents)); |
| } |
| |
| // Retrieves the instance of type T that was attached to the specified |
| // WebContents (via CreateForWebContents above) and returns it. If no instance |
| // of the type was attached, returns nullptr. |
| static T* FromWebContents(WebContents* contents) { |
| DCHECK(contents); |
| return static_cast<T*>(contents->GetUserData(UserDataKey())); |
| } |
| static const T* FromWebContents(const WebContents* contents) { |
| DCHECK(contents); |
| return static_cast<const T*>(contents->GetUserData(UserDataKey())); |
| } |
| |
| protected: |
| static inline void* UserDataKey() { |
| return &kLocatorKey; |
| } |
| |
| private: |
| // The user data key. |
| static int kLocatorKey; |
| }; |
| |
| // The macro to define the locator key. This key must be defined in the .cc file |
| // of the tab helper otherwise different instances for different template types |
| // will be collapsed by the Visual Studio linker. |
| // |
| // The "= 0" is surprising, but is required to effect a definition rather than |
| // a declaration. Without it, this would be merely a declaration of a template |
| // specialization. (C++98: 14.7.3.15; C++11: 14.7.3.13) |
| // |
| #define DEFINE_WEB_CONTENTS_USER_DATA_KEY(TYPE) \ |
| template<> \ |
| int content::WebContentsUserData<TYPE>::kLocatorKey = 0 |
| |
| } // namespace content |
| |
| #endif // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_USER_DATA_H_ |