1 // Copyright (c) 2011 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 // ScopedCallbackFactory helps in cases where you wish to allocate a Callback 6 // (see base/callback.h), but need to prevent any pending callbacks from 7 // executing when your object gets destroyed. 8 // 9 // EXAMPLE: 10 // 11 // void GatherDataAsynchronously(Callback1<Data>::Type* callback); 12 // 13 // class MyClass { 14 // public: 15 // MyClass() : factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) { 16 // } 17 // 18 // void Process() { 19 // GatherDataAsynchronously(factory_.NewCallback(&MyClass::GotData)); 20 // } 21 // 22 // private: 23 // void GotData(const Data& data) { 24 // ... 25 // } 26 // 27 // base::ScopedCallbackFactory<MyClass> factory_; 28 // }; 29 // 30 // In the above example, the Process function calls GatherDataAsynchronously to 31 // kick off some asynchronous processing that upon completion will notify a 32 // callback. If in the meantime, the MyClass instance is destroyed, when the 33 // callback runs, it will notice that the MyClass instance is dead, and it will 34 // avoid calling the GotData method. 35 36 #ifndef BASE_MEMORY_SCOPED_CALLBACK_FACTORY_H_ 37 #define BASE_MEMORY_SCOPED_CALLBACK_FACTORY_H_ 38 39 #include "base/callback.h" 40 #include "base/memory/weak_ptr.h" 41 42 namespace base { 43 44 template <class T> 45 class ScopedCallbackFactory { 46 public: ScopedCallbackFactory(T * obj)47 explicit ScopedCallbackFactory(T* obj) : weak_factory_(obj) { 48 } 49 NewCallback(void (T::* method)())50 typename Callback0::Type* NewCallback( 51 void (T::*method)()) { 52 return new CallbackImpl<void (T::*)(), Tuple0 >( 53 weak_factory_.GetWeakPtr(), method); 54 } 55 56 template <typename Arg1> NewCallback(void (T::* method)(Arg1))57 typename Callback1<Arg1>::Type* NewCallback( 58 void (T::*method)(Arg1)) { 59 return new CallbackImpl<void (T::*)(Arg1), Tuple1<Arg1> >( 60 weak_factory_.GetWeakPtr(), method); 61 } 62 63 template <typename Arg1, typename Arg2> NewCallback(void (T::* method)(Arg1,Arg2))64 typename Callback2<Arg1, Arg2>::Type* NewCallback( 65 void (T::*method)(Arg1, Arg2)) { 66 return new CallbackImpl<void (T::*)(Arg1, Arg2), Tuple2<Arg1, Arg2> >( 67 weak_factory_.GetWeakPtr(), method); 68 } 69 70 template <typename Arg1, typename Arg2, typename Arg3> NewCallback(void (T::* method)(Arg1,Arg2,Arg3))71 typename Callback3<Arg1, Arg2, Arg3>::Type* NewCallback( 72 void (T::*method)(Arg1, Arg2, Arg3)) { 73 return new CallbackImpl<void (T::*)(Arg1, Arg2, Arg3), 74 Tuple3<Arg1, Arg2, Arg3> >( 75 weak_factory_.GetWeakPtr(), method); 76 } 77 78 template <typename Arg1, typename Arg2, typename Arg3, typename Arg4> NewCallback(void (T::* method)(Arg1,Arg2,Arg3,Arg4))79 typename Callback4<Arg1, Arg2, Arg3, Arg4>::Type* NewCallback( 80 void (T::*method)(Arg1, Arg2, Arg3, Arg4)) { 81 return new CallbackImpl<void (T::*)(Arg1, Arg2, Arg3, Arg4), 82 Tuple4<Arg1, Arg2, Arg3, Arg4> >( 83 weak_factory_.GetWeakPtr(), method); 84 } 85 86 template <typename Arg1, typename Arg2, typename Arg3, typename Arg4, 87 typename Arg5> NewCallback(void (T::* method)(Arg1,Arg2,Arg3,Arg4,Arg5))88 typename Callback5<Arg1, Arg2, Arg3, Arg4, Arg5>::Type* NewCallback( 89 void (T::*method)(Arg1, Arg2, Arg3, Arg4, Arg5)) { 90 return new CallbackImpl<void (T::*)(Arg1, Arg2, Arg3, Arg4, Arg5), 91 Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> >( 92 weak_factory_.GetWeakPtr(), method); 93 } 94 RevokeAll()95 void RevokeAll() { weak_factory_.InvalidateWeakPtrs(); } HasPendingCallbacks()96 bool HasPendingCallbacks() const { return weak_factory_.HasWeakPtrs(); } 97 98 private: 99 template <typename Method> 100 class CallbackStorage { 101 public: CallbackStorage(const WeakPtr<T> & obj,Method meth)102 CallbackStorage(const WeakPtr<T>& obj, Method meth) 103 : obj_(obj), 104 meth_(meth) { 105 } 106 107 protected: 108 WeakPtr<T> obj_; 109 Method meth_; 110 }; 111 112 template <typename Method, typename Params> 113 class CallbackImpl : public CallbackStorage<Method>, 114 public CallbackRunner<Params> { 115 public: CallbackImpl(const WeakPtr<T> & obj,Method meth)116 CallbackImpl(const WeakPtr<T>& obj, Method meth) 117 : CallbackStorage<Method>(obj, meth) { 118 } RunWithParams(const Params & params)119 virtual void RunWithParams(const Params& params) { 120 // Use "this->" to force C++ to look inside our templatized base class; 121 // see Effective C++, 3rd Ed, item 43, p210 for details. 122 if (!this->obj_) 123 return; 124 DispatchToMethod(this->obj_.get(), this->meth_, params); 125 } 126 }; 127 128 WeakPtrFactory<T> weak_factory_; 129 }; 130 131 } // namespace base 132 133 #endif // BASE_MEMORY_SCOPED_CALLBACK_FACTORY_H_ 134