Banish boilerplate. Profile-keyed API factory for extension API classes.

chrome/browser/extensions/api/profile_keyed_api_factory.h

+// 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 CHROME_BROWSER_EXTENSIONS_API_PROFILE_KEYED_API_FACTORY_H_
+#define CHROME_BROWSER_EXTENSIONS_API_PROFILE_KEYED_API_FACTORY_H_
+
+#include "base/lazy_instance.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/extensions/extension_system_factory.h"
+#include "chrome/browser/profiles/profile_dependency_manager.h"
+#include "chrome/browser/profiles/profile_keyed_service_factory.h"
+
+namespace extensions {
+
+// Default settings for instantiations of ProfileKeyedAPIFactory.
+struct DefaultProfileKeyedAPIFactoryTraits {
+  // Flags that control ProfileKeyedAPIFactory behavior.
+  // See ProfileKeyedBaseFactory for usage.
+  static const bool kServiceRedirectedInIncognito = false;
+  static const bool kServiceIsNULLWhileTesting = false;
+};
+
+// Instantiations of ProfileKeyedAPIFactory must specialize this traits class
+// and declare a static const char* name() function (used in the
+// ProfileKeyedBase constructor). They can also override flags from
+// DefaultProfileKeyedAPIFactoryTraits.
+template <typename T>
+struct ProfileKeyedAPIFactoryTraits
+    : public DefaultProfileKeyedAPIFactoryTraits {
+};
+
+// A template for factories for Profile-keyed services that manage
+// extension APIs.
+template <typename T>

[Jeffrey Yasskin, 2012/12/21 01:43:50]

Document what T is.

Can you make the trait fields into static members of T instead of making people
specialize ProfileKeyedAPIFactoryTraits?

[Yoyo Zhou, 2012/12/21 22:41:33]

Expanded the comment.

If I make them static members of T, then in order to have default properties, I
need to define a ProfileKeyedService base here that the Ts inherit from.

I'll upload 2 patchsets:

3: leaving this as is
4: making the traits static members of ProfileKeyedAPI (inherits from
ProfileKeyedService)

+class ProfileKeyedAPIFactory : public ProfileKeyedServiceFactory {
+ public:
+  typedef ProfileKeyedAPIFactoryTraits<T> Traits;
+
+  static T* GetForProfile(Profile* profile) {
+    return static_cast<T*>(
+        GetInstance()->GetServiceForProfile(profile, true));
+  }
+
+  static ProfileKeyedAPIFactory<T>* GetInstance() {
+    if (!instance_.Get())
+      instance_.Get().reset(new ProfileKeyedAPIFactory<T>);
+    return instance_.Get().get();
+  }
+
+  // Declare dependencies on other factories.
+  // By default, ExtensionSystemFactory is the only dependency; however,
+  // specializations can override this.

[Jeffrey Yasskin, 2012/12/21 01:43:50]

Give some example code for how they'd override it.

[Yoyo Zhou, 2012/12/21 22:41:33]

Done.

+  void DeclareFactoryDependencies() {
+    DependsOn(extensions::ExtensionSystemFactory::GetInstance());
+  }
+
+  ProfileKeyedAPIFactory<T>()
+  : ProfileKeyedServiceFactory(Traits::name(),
+                               ProfileDependencyManager::GetInstance()) {
+    DeclareFactoryDependencies();
+  }
+
+  virtual ~ProfileKeyedAPIFactory<T>() {

[Jeffrey Yasskin, 2012/12/21 01:43:50]

s/<T>//. C++ expands the plain name of the current template to the current
specialization.

[Yoyo Zhou, 2012/12/21 22:41:33]

Done throughout.

+  }
+
+ private:
+  friend class scoped_ptr<ProfileKeyedAPIFactory<T> >;
+
+  // ProfileKeyedServiceFactory implementation.
+  virtual ProfileKeyedService* BuildServiceInstanceFor(
+      Profile* profile) const OVERRIDE {
+    return new T(profile);
+  }
+
+  // ProfileKeyedBaseFactory implementation.
+  // These can be effectively overridden with template specializations.
+  virtual bool ServiceRedirectedInIncognito() const OVERRIDE {
+    return Traits::kServiceRedirectedInIncognito;
+  }
+
+  virtual bool ServiceIsCreatedWithProfile() const OVERRIDE {
+    return true;
+  }
+
+  virtual bool ServiceIsNULLWhileTesting() const OVERRIDE {
+    return Traits::kServiceIsNULLWhileTesting;
+  }
+
+  static base::LazyInstance<scoped_ptr<ProfileKeyedAPIFactory<T> > >

[Jeffrey Yasskin, 2012/12/21 01:43:50]

Why LazyInstance<scoped_ptr>? Do you want LazyInstance<ProfileKeyedAPIFactory<T>
>::Leaky?

[Yoyo Zhou, 2012/12/21 22:41:33]

Can't be done here:

invalid application of 'sizeof' to incomplete type
'extensions::ProfileKeyedAPIFactory<extensions::ProcessesAPI

The alternative to this scoped_ptr shenanigan is declaring the lazy instance in
each instantiator. I went and did that. I'm not certain that leakiness matters
for my use case.

+      instance_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProfileKeyedAPIFactory<T>);
+};
+
+template <typename T>
+base::LazyInstance<scoped_ptr<ProfileKeyedAPIFactory<T> > >
+ProfileKeyedAPIFactory<T>::instance_ = LAZY_INSTANCE_INITIALIZER;

[Jeffrey Yasskin, 2012/12/21 01:43:50]

This is going to be sad if it's #included from multiple DLLs. You'll get
multiple instances.

[Yoyo Zhou, 2012/12/21 22:41:33]

Moved the lazy instances to each .cc file.

+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_PROFILE_KEYED_API_FACTORY_H_