add Create for scope

paddle/framework/scope.h

@@ -31,10 +31,16 @@ namespace framework {
  * scope.
  */
 class Scope {
- public:
+ private:
   explicit Scope(const std::shared_ptr<Scope>& parent = nullptr)
       : parent_(parent) {}
 
+ public:
+  static std::shared_ptr<Scope> Create(
+      const std::shared_ptr<Scope>& parent = nullptr) {
+    return std::make_shared<Scope>(Scope(parent));
+  }
+
   /// Create Variable in this Scope. Failed if Variable already been
   /// created.
   Variable* CreateVariable(const std::string& name) {

paddle/framework/scope_test.cc

@@ -19,7 +19,7 @@ TEST(Scope, Create) {
   using paddle::framework::Scope;
   using paddle::framework::Variable;
 
-  Scope* scope = new Scope();
+  auto scope = Scope::Create();
 
   Variable* var0 = scope->CreateVariable("");
   EXPECT_NE(var0, nullptr);
@@ -42,10 +42,10 @@ TEST(Scope, Parent) {
   using paddle::framework::Scope;
   using paddle::framework::Variable;
 
-  const auto parent_scope_ptr = std::shared_ptr<Scope>(new Scope());
-  Scope* scope = new Scope(parent_scope_ptr);
+  auto parent_scope = Scope::Create();
+  auto scope = Scope::Create(parent_scope);
 
-  Variable* var0 = parent_scope_ptr->CreateVariable("a");
+  Variable* var0 = parent_scope->CreateVariable("a");
   EXPECT_NE(var0, nullptr);
 
   Variable* var1 = scope->GetVariable("a");