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.
5 #ifndef IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_
6 #define IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_
8 #include "ios/public/consumer/base/supports_user_data.h"
9 #include "ios/public/provider/web/web_state.h"
13 // A base class for classes attached to, and scoped to, the lifetime of a
14 // WebState. For example:
17 // class Foo : public ios::WebStateUserData<Foo> {
20 // // ... more public stuff here ...
22 // explicit Foo(ios::WebState* web_state);
23 // friend class ios::WebStateUserData<Foo>;
24 // // ... more private stuff here ...
27 // DEFINE_WEB_CONTENTS_USER_DATA_KEY(Foo);
30 class WebStateUserData : public ios::SupportsUserData::Data {
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));
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()));
45 static const T* FromWebState(const WebState* web_state) {
46 return static_cast<const T*>(web_state->GetUserData(UserDataKey()));
50 static inline void* UserDataKey() {
56 static int kLocatorKey;
59 // The macro to define the locator key. This key should be defined in the .cc
60 // file of the derived class.
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)
66 #define DEFINE_WEB_STATE_USER_DATA_KEY(TYPE) \
68 int ios::WebStateUserData<TYPE>::kLocatorKey = 0
72 #endif // IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_