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_WEB_PUBLIC_WEB_STATE_USER_DATA_H_ 6 #define IOS_WEB_PUBLIC_WEB_STATE_USER_DATA_H_ 7 8 #include "base/memory/ptr_util.h" 9 #include "base/supports_user_data.h" 10 #import "ios/web/public/web_state.h" 11 12 // This macro declares a static variable inside the class that inherits from 13 // WebStateUserData. The address of this static variable is used as the key to 14 // store/retrieve an instance of the class on/from a WebState. 15 #define WEB_STATE_USER_DATA_KEY_DECL() static constexpr int kUserDataKey = 0 16 17 // This macro instantiates the static variable declared by the previous macro. 18 // It must live in a .mm/.cc file to ensure that there is only one instantiation 19 // of the static variable. 20 #define WEB_STATE_USER_DATA_KEY_IMPL(Type) const int Type::kUserDataKey; 21 22 namespace web { 23 24 // A base class for classes attached to, and scoped to, the lifetime of a 25 // WebState. For example: 26 // 27 // --- in foo_tab_helper.h --- 28 // class FooTabHelper : public web::WebStateUserData<FooTabHelper> { 29 // public: 30 // ~FooTabHelper() override; 31 // // ... more public stuff here ... 32 // private: 33 // explicit FooTabHelper(web::WebState* web_state); 34 // friend class web::WebStateUserData<FooTabHelper>; 35 // WEB_STATE_USER_DATA_KEY_DECL(); 36 // // ... more private stuff here ... 37 // }; 38 // 39 // --- in foo_tab_helper.cc --- 40 // WEB_STATE_USER_DATA_KEY_IMPL(FooTabHelper) 41 template <typename T> 42 class WebStateUserData : public base::SupportsUserData::Data { 43 public: 44 // Creates an object of type T, and attaches it to the specified WebState. 45 // If an instance is already attached, does nothing. CreateForWebState(WebState * web_state)46 static void CreateForWebState(WebState* web_state) { 47 if (!FromWebState(web_state)) 48 web_state->SetUserData(UserDataKey(), base::WrapUnique(new T(web_state))); 49 } 50 51 // Retrieves the instance of type T that was attached to the specified 52 // WebState (via CreateForWebState above) and returns it. If no instance 53 // of the type was attached, returns nullptr. FromWebState(WebState * web_state)54 static T* FromWebState(WebState* web_state) { 55 return static_cast<T*>(web_state->GetUserData(UserDataKey())); 56 } FromWebState(const WebState * web_state)57 static const T* FromWebState(const WebState* web_state) { 58 return static_cast<const T*>(web_state->GetUserData(UserDataKey())); 59 } 60 61 // Removes the instance attached to the specified WebState. RemoveFromWebState(WebState * web_state)62 static void RemoveFromWebState(WebState* web_state) { 63 web_state->RemoveUserData(UserDataKey()); 64 } 65 UserDataKey()66 static const void* UserDataKey() { return &T::kUserDataKey; } 67 }; 68 69 } // namespace web 70 71 #endif // IOS_WEB_PUBLIC_WEB_STATE_USER_DATA_H_ 72