Add base::ScopedObservation.
This class is for observers that observe only one source.
This is more readable and slightly more efficient than using
base::ScopedObserver, where an observer has zero or one subscriptions.
Change-Id: Iefd987ce006aa2106249cf2708f63d90326814ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2518028
Reviewed-by: François Doray <[email protected]>
Reviewed-by: Patrick Monette <[email protected]>
Commit-Queue: François Doray <[email protected]>
Commit-Queue: Sigurður Ásgeirsson <[email protected]>
Cr-Commit-Position: refs/heads/master@{#824014}
diff --git a/base/scoped_observation_unittest.cc b/base/scoped_observation_unittest.cc
new file mode 100644
index 0000000..37ca30e
--- /dev/null
+++ b/base/scoped_observation_unittest.cc
@@ -0,0 +1,147 @@
+// Copyright 2020 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.
+
+#include "base/scoped_observation.h"
+
+#include "base/ranges/algorithm.h"
+#include "base/stl_util.h"
+#include "base/test/gtest_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace {
+
+class TestSourceObserver {};
+
+class TestSource {
+ public:
+ void AddObserver(TestSourceObserver* observer);
+ void RemoveObserver(TestSourceObserver* observer);
+
+ bool HasObserver(TestSourceObserver* observer) const;
+ size_t num_observers() const { return observers_.size(); }
+
+ private:
+ std::vector<TestSourceObserver*> observers_;
+};
+
+void TestSource::AddObserver(TestSourceObserver* observer) {
+ observers_.push_back(observer);
+}
+
+void TestSource::RemoveObserver(TestSourceObserver* observer) {
+ auto it = base::ranges::find(observers_, observer);
+ EXPECT_TRUE(it != observers_.end());
+ observers_.erase(it);
+}
+
+bool TestSource::HasObserver(TestSourceObserver* observer) const {
+ return base::Contains(observers_, observer);
+}
+
+using TestScopedObservation = ScopedObservation<TestSource, TestSourceObserver>;
+
+} // namespace
+
+TEST(ScopedObservationTest, RemovesObservationOnDestruction) {
+ TestSource s1;
+
+ {
+ TestSourceObserver o1;
+ TestScopedObservation obs(&o1);
+ EXPECT_EQ(0u, s1.num_observers());
+ EXPECT_FALSE(s1.HasObserver(&o1));
+
+ obs.Observe(&s1);
+ EXPECT_EQ(1u, s1.num_observers());
+ EXPECT_TRUE(s1.HasObserver(&o1));
+ }
+
+ // Test that the observation is removed when it goes out of scope.
+ EXPECT_EQ(0u, s1.num_observers());
+}
+
+TEST(ScopedObservationTest, RemoveObservation) {
+ TestSource s1;
+ TestSourceObserver o1;
+ TestScopedObservation obs(&o1);
+ EXPECT_EQ(0u, s1.num_observers());
+ EXPECT_FALSE(s1.HasObserver(&o1));
+
+ obs.Observe(&s1);
+ EXPECT_EQ(1u, s1.num_observers());
+ EXPECT_TRUE(s1.HasObserver(&o1));
+
+ obs.RemoveObservation();
+ EXPECT_EQ(0u, s1.num_observers());
+}
+
+TEST(ScopedObservationTest, IsObserving) {
+ TestSource s1;
+ TestSourceObserver o1;
+ TestScopedObservation obs(&o1);
+ EXPECT_FALSE(obs.IsObserving());
+
+ obs.Observe(&s1);
+ EXPECT_TRUE(obs.IsObserving());
+
+ obs.RemoveObservation();
+ EXPECT_FALSE(obs.IsObserving());
+}
+
+TEST(ScopedObservationTest, IsObservingSource) {
+ TestSource s1;
+ TestSource s2;
+ TestSourceObserver o1;
+ TestScopedObservation obs(&o1);
+ EXPECT_FALSE(obs.IsObservingSource(&s1));
+ EXPECT_FALSE(obs.IsObservingSource(&s2));
+
+ obs.Observe(&s1);
+ EXPECT_TRUE(obs.IsObservingSource(&s1));
+ EXPECT_FALSE(obs.IsObservingSource(&s2));
+
+ obs.RemoveObservation();
+ EXPECT_FALSE(obs.IsObservingSource(&s1));
+ EXPECT_FALSE(obs.IsObservingSource(&s2));
+}
+
+namespace {
+
+// A test source with oddly named Add/Remove functions.
+class TestSourceWithNonDefaultNames {
+ public:
+ void AddFoo(TestSourceObserver* observer) { impl_.AddObserver(observer); }
+ void RemoveFoo(TestSourceObserver* observer) {
+ impl_.RemoveObserver(observer);
+ }
+
+ const TestSource& impl() const { return impl_; }
+
+ private:
+ TestSource impl_;
+};
+
+using TestScopedObservationWithNonDefaultNames =
+ ScopedObservation<TestSourceWithNonDefaultNames,
+ TestSourceObserver,
+ &TestSourceWithNonDefaultNames::AddFoo,
+ &TestSourceWithNonDefaultNames::RemoveFoo>;
+
+} // namespace
+
+TEST(ScopedObservationTest, NonDefaultNames) {
+ TestSourceWithNonDefaultNames s1;
+ TestSourceObserver o1;
+
+ EXPECT_EQ(0u, s1.impl().num_observers());
+ {
+ TestScopedObservationWithNonDefaultNames obs(&o1);
+ obs.Observe(&s1);
+ EXPECT_EQ(1u, s1.impl().num_observers());
+ EXPECT_TRUE(s1.impl().HasObserver(&o1));
+ }
+}
+
+} // namespace base
