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Introduce variable_value::as_optional<>() #87

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Introduce variable_value::as_optional<>() #87

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11 changes: 11 additions & 0 deletions include/boost/program_options/variables_map.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@

#include <boost/any.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/optional.hpp>

#include <string>
#include <map>
Expand Down Expand Up @@ -74,6 +75,16 @@ namespace boost { namespace program_options {
return boost::any_cast<T&>(v);
}

/** If stored value is of type T, returns optional<T> having that value.
If variable is empty, returns optional<T> having the none.
Otherwise, throws boost::bad_any_cast exception. */
template<class T>
optional<T> as_optional() const {
if (empty()) return none;

return as<T>();
}

/// Returns true if no value is stored.
bool empty() const;
/** Returns true if the value was not explicitly
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4 changes: 4 additions & 0 deletions test/variable_map_test.cpp
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Expand Up @@ -51,6 +51,8 @@ void test_variable_map()
BOOST_CHECK(vm.count("biz") == 1);
BOOST_CHECK(vm["biz"].as<string>() == "3");
BOOST_CHECK(vm["output"].as<string>() == "foo");
BOOST_CHECK(vm["bar"].as_optional<string>() == optional<string>("11"));
BOOST_CHECK(vm["buz"].as_optional<string>() == none);

int i;
desc.add_options()
Expand All @@ -71,6 +73,8 @@ void test_variable_map()
BOOST_CHECK(vm2["zak"].as<int>() == 13);
BOOST_CHECK(vm2["opt"].as<bool>() == false);
BOOST_CHECK(i == 13);
BOOST_CHECK(vm2["zak"].as_optional<int>() == optional<int>(13));
BOOST_CHECK(vm2["zoo"].as_optional<int>() == none);

options_description desc2;
desc2.add_options()
Expand Down