Easier ftl::Flags construction
As demonstrated by the existing test, while it is possible to construct
a ftl::Flags<E> from multiple values, it requires an extra
`using namespace ftl::flag_operators` or alternatively a
`using ftl::flag_operators::operator|` to implicitly construct a
`ftl::Flags<E>` type.
But there is an easier way -- allow implicit construction from a
`std::initializer_list<E>`.
This means as an alternative to:
using namespace ftl::flag_operators;
ftl::Flags<E> x = E::A | E::B;
... one can instead write:
ftl::Flags<E> x = {E::A, E::B};
... and achieve the same initial value.
This change adds the new constructor overload.
Assignment from an initializer list automatically works, without having
to define a explicit `operator=(std::initializer_list<E>)`. Instead the
copy constuctor is used.
As a useful side effect, you can now also clear the flags by assigning
an empty initializer list:
ftl::Flags<E> x;
x = {}; // Clears x to zero
Bug: 185536303
Flag: EXEMPT New library code
Test: atest ftl_test
Change-Id: I1de7857c93ebef4fc5e6157aac9cf162b49943e1
diff --git a/libs/ftl/flags_test.cpp b/libs/ftl/flags_test.cpp
index 1279d11..bb43e8d 100644
--- a/libs/ftl/flags_test.cpp
+++ b/libs/ftl/flags_test.cpp
@@ -17,7 +17,7 @@
#include <ftl/flags.h>
#include <gtest/gtest.h>
-#include <type_traits>
+#include <initializer_list>
namespace android::test {
@@ -59,6 +59,18 @@
ASSERT_FALSE(flags.all(TestFlags::ONE | TestFlags::TWO | TestFlags::THREE));
}
+TEST(Flags, ImplicitConstructionAndAssignmentFromInitializerList) {
+ Flags<TestFlags> flags = {TestFlags::ONE, TestFlags::THREE};
+ ASSERT_TRUE(flags.test(TestFlags::ONE));
+ ASSERT_FALSE(flags.test(TestFlags::TWO));
+ ASSERT_TRUE(flags.test(TestFlags::THREE));
+
+ flags = {};
+ ASSERT_FALSE(flags.test(TestFlags::ONE));
+ ASSERT_FALSE(flags.test(TestFlags::TWO));
+ ASSERT_FALSE(flags.test(TestFlags::THREE));
+}
+
TEST(Flags, DefaultConstructor_hasNoFlagsSet) {
Flags<TestFlags> flags;
ASSERT_FALSE(flags.any(TestFlags::ONE | TestFlags::TWO | TestFlags::THREE));