Make Callback::Reset() return a copy to support use-cases where Run() ends up modifying |*this|.

base/callback.h

 // This file was GENERATED by command:
 //     pump.py callback.h.pump
 // DO NOT EDIT BY HAND!!!
 
 
 // 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 BASE_CALLBACK_H_
@@ skipping 21 matching lines @@
 //
 // MEMORY MANAGEMENT AND PASSING
 //
 // The Callback objects themselves should be passed by const-reference, and
 // stored by copy. They internally store their state via a refcounted class
 // and thus do not need to be deleted.
 //
 // The reason to pass via a const-reference is to avoid unnecessary
 // AddRef/Release pairs to the internal state.
 //
+// If a Callback variable must be empty during the Run() of a previous value of
+// that variable, use ResetAndRun().  E.g. if MyClass has a member variable
+// Callback which gets set as a side-effect of Run()'ing the Callback (to
+// something else), ResetAndRun() can be handy.
 //
 // EXAMPLE USAGE:
 //
 // /* Binding a normal function. */
 // int Return5() { return 5; }
 // base::Callback<int(void)> func_cb = base::Bind(&Return5);
 // LOG(INFO) << func_cb.Run();  // Prints 5.
 //
 // void PrintHi() { LOG(INFO) << "hi."; }
 // base::Closure void_func_cb = base::Bind(&PrintHi);
@@ skipping 213 matching lines @@
     return CallbackBase::Equals(other);
   }
 
   R Run() const {
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get());
   }
 
+
+  R ResetAndRun() {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run();
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*);
 
 };
 
 template <typename R, typename A1>
 class Callback<R(A1)> : public internal::CallbackBase {
  public:
   typedef R(RunType)(A1);
@@ skipping 19 matching lines @@
     return CallbackBase::Equals(other);
   }
 
   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1) const {
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get(), internal::CallbackForward(a1));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType);
 
 };
 
 template <typename R, typename A1, typename A2>
 class Callback<R(A1, A2)> : public internal::CallbackBase {
  public:
@@ skipping 22 matching lines @@
 
   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
         typename internal::CallbackParamTraits<A2>::ForwardType a2) const {
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get(), internal::CallbackForward(a1),
              internal::CallbackForward(a2));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1),
+            internal::CallbackForward(a2));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType,
           typename internal::CallbackParamTraits<A2>::ForwardType);
 
 };
 
 template <typename R, typename A1, typename A2, typename A3>
 class Callback<R(A1, A2, A3)> : public internal::CallbackBase {
@@ skipping 25 matching lines @@
         typename internal::CallbackParamTraits<A2>::ForwardType a2,
         typename internal::CallbackParamTraits<A3>::ForwardType a3) const {
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get(), internal::CallbackForward(a1),
              internal::CallbackForward(a2),
              internal::CallbackForward(a3));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2,
+        typename internal::CallbackParamTraits<A3>::ForwardType a3) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1),
+            internal::CallbackForward(a2),
+            internal::CallbackForward(a3));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType,
           typename internal::CallbackParamTraits<A2>::ForwardType,
           typename internal::CallbackParamTraits<A3>::ForwardType);
 
 };
 
 template <typename R, typename A1, typename A2, typename A3, typename A4>
@@ skipping 28 matching lines @@
         typename internal::CallbackParamTraits<A4>::ForwardType a4) const {
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get(), internal::CallbackForward(a1),
              internal::CallbackForward(a2),
              internal::CallbackForward(a3),
              internal::CallbackForward(a4));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2,
+        typename internal::CallbackParamTraits<A3>::ForwardType a3,
+        typename internal::CallbackParamTraits<A4>::ForwardType a4) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1),
+            internal::CallbackForward(a2),
+            internal::CallbackForward(a3),
+            internal::CallbackForward(a4));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType,
           typename internal::CallbackParamTraits<A2>::ForwardType,
           typename internal::CallbackParamTraits<A3>::ForwardType,
           typename internal::CallbackParamTraits<A4>::ForwardType);
 
 };
 
@@ skipping 32 matching lines @@
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get(), internal::CallbackForward(a1),
              internal::CallbackForward(a2),
              internal::CallbackForward(a3),
              internal::CallbackForward(a4),
              internal::CallbackForward(a5));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2,
+        typename internal::CallbackParamTraits<A3>::ForwardType a3,
+        typename internal::CallbackParamTraits<A4>::ForwardType a4,
+        typename internal::CallbackParamTraits<A5>::ForwardType a5) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1),
+            internal::CallbackForward(a2),
+            internal::CallbackForward(a3),
+            internal::CallbackForward(a4),
+            internal::CallbackForward(a5));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType,
           typename internal::CallbackParamTraits<A2>::ForwardType,
           typename internal::CallbackParamTraits<A3>::ForwardType,
           typename internal::CallbackParamTraits<A4>::ForwardType,
           typename internal::CallbackParamTraits<A5>::ForwardType);
 
 };
@@ skipping 35 matching lines @@
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
     return f(bind_state_.get(), internal::CallbackForward(a1),
              internal::CallbackForward(a2),
              internal::CallbackForward(a3),
              internal::CallbackForward(a4),
              internal::CallbackForward(a5),
              internal::CallbackForward(a6));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2,
+        typename internal::CallbackParamTraits<A3>::ForwardType a3,
+        typename internal::CallbackParamTraits<A4>::ForwardType a4,
+        typename internal::CallbackParamTraits<A5>::ForwardType a5,
+        typename internal::CallbackParamTraits<A6>::ForwardType a6) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1),
+            internal::CallbackForward(a2),
+            internal::CallbackForward(a3),
+            internal::CallbackForward(a4),
+            internal::CallbackForward(a5),
+            internal::CallbackForward(a6));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType,
           typename internal::CallbackParamTraits<A2>::ForwardType,
           typename internal::CallbackParamTraits<A3>::ForwardType,
           typename internal::CallbackParamTraits<A4>::ForwardType,
           typename internal::CallbackParamTraits<A5>::ForwardType,
           typename internal::CallbackParamTraits<A6>::ForwardType);
 
@@ skipping 38 matching lines @@
 
     return f(bind_state_.get(), internal::CallbackForward(a1),
              internal::CallbackForward(a2),
              internal::CallbackForward(a3),
              internal::CallbackForward(a4),
              internal::CallbackForward(a5),
              internal::CallbackForward(a6),
              internal::CallbackForward(a7));
   }
 
+
+  R ResetAndRun(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2,
+        typename internal::CallbackParamTraits<A3>::ForwardType a3,
+        typename internal::CallbackParamTraits<A4>::ForwardType a4,
+        typename internal::CallbackParamTraits<A5>::ForwardType a5,
+        typename internal::CallbackParamTraits<A6>::ForwardType a6,
+        typename internal::CallbackParamTraits<A7>::ForwardType a7) {
+    Callback<RunType> tmp(*this);
+    Reset();
+    tmp.Run(internal::CallbackForward(a1),
+            internal::CallbackForward(a2),
+            internal::CallbackForward(a3),
+            internal::CallbackForward(a4),
+            internal::CallbackForward(a5),
+            internal::CallbackForward(a6),
+            internal::CallbackForward(a7));
+  }
+
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
           typename internal::CallbackParamTraits<A1>::ForwardType,
           typename internal::CallbackParamTraits<A2>::ForwardType,
           typename internal::CallbackParamTraits<A3>::ForwardType,
           typename internal::CallbackParamTraits<A4>::ForwardType,
           typename internal::CallbackParamTraits<A5>::ForwardType,
           typename internal::CallbackParamTraits<A6>::ForwardType,
           typename internal::CallbackParamTraits<A7>::ForwardType);
 
 };
 
 
 // Syntactic sugar to make Callbacks<void(void)> easier to declare since it
 // will be used in a lot of APIs with delayed execution.
 typedef Callback<void(void)> Closure;
 
 }  // namespace base
 
 #endif  // BASE_CALLBACK_H