1// Copyright 2013 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_ 6#define IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_ 7 8#include "ios/public/consumer/base/supports_user_data.h" 9#include "ios/public/provider/web/web_state.h" 10 11namespace ios { 12 13// A base class for classes attached to, and scoped to, the lifetime of a 14// WebState. For example: 15// 16// --- in foo.h --- 17// class Foo : public ios::WebStateUserData<Foo> { 18// public: 19// virtual ~Foo(); 20// // ... more public stuff here ... 21// private: 22// explicit Foo(ios::WebState* web_state); 23// friend class ios::WebStateUserData<Foo>; 24// // ... more private stuff here ... 25// } 26// --- in foo.cc --- 27// DEFINE_WEB_CONTENTS_USER_DATA_KEY(Foo); 28// 29template <typename T> 30class WebStateUserData : public ios::SupportsUserData::Data { 31 public: 32 // Creates an object of type T, and attaches it to the specified WebState. 33 // If an instance is already attached, does nothing. 34 static void CreateForWebState(WebState* web_state) { 35 if (!FromWebState(web_state)) 36 web_state->SetUserData(UserDataKey(), new T(web_state)); 37 } 38 39 // Retrieves the instance of type T that was attached to the specified 40 // WebState (via CreateForWebState above) and returns it. If no instance 41 // of the type was attached, returns NULL. 42 static T* FromWebState(WebState* web_state) { 43 return static_cast<T*>(web_state->GetUserData(UserDataKey())); 44 } 45 static const T* FromWebState(const WebState* web_state) { 46 return static_cast<const T*>(web_state->GetUserData(UserDataKey())); 47 } 48 49 protected: 50 static inline void* UserDataKey() { 51 return &kLocatorKey; 52 } 53 54 private: 55 // The user data key. 56 static int kLocatorKey; 57}; 58 59// The macro to define the locator key. This key should be defined in the .cc 60// file of the derived class. 61// 62// The "= 0" is surprising, but is required to effect a definition rather than 63// a declaration. Without it, this would be merely a declaration of a template 64// specialization. (C++98: 14.7.3.15; C++11: 14.7.3.13) 65// 66#define DEFINE_WEB_STATE_USER_DATA_KEY(TYPE) \ 67template<> \ 68int ios::WebStateUserData<TYPE>::kLocatorKey = 0 69 70} // namespace ios 71 72#endif // IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_ 73