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Merge pull request #38 from ToruNiina/get-any-type

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extended conversions
This commit is contained in:
Toru Niina
2019-03-17 13:11:59 +09:00
committed by GitHub
parent 0908806915 cad8f51256
commit d86870e038
8 changed files with 405 additions and 0 deletions
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142
README.md
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@@ -457,6 +457,148 @@ int i = 0;
toml::from_toml(i, data.at("something"));
```
### Conversion between toml value and your class
You can also use `toml::get` and other related functions with the types you defined
after you implement some stuff.
```cpp
namespace ext
{
struct foo
{
int a;
double b;
std::string c;
};
} // ext
const auto data = toml::parse("example.toml");
const foo f = toml::get<ext::foo>(data.at("foo"));
```
There are 2 ways to use `toml::get` with the types that you defined.
The first one is to implement `from_toml(const toml::value&)` member function.
```cpp
namespace ext
{
struct foo
{
int a;
double b;
std::string c;
void from_toml(const toml::value& v)
{
this->a = toml::find<int >(v, "a");
this->b = toml::find<double >(v, "b");
this->c = toml::find<std::string>(v, "c");
return;
}
};
} // ext
```
In this way, because `toml::get` first constructs `foo` without arguments,
the type should be default-constructible.
The second is to implement specialization of `toml::from` for your type.
```cpp
namespace ext
{
struct foo
{
int a;
double b;
std::string c;
};
} // ext
namespace toml
{
template<>
struct from<ext::foo>
{
ext::foo from_toml(const toml::value& v)
{
ext::foo f;
f.a = toml::find<int >(v, "a");
f.b = toml::find<double >(v, "b");
f.c = toml::find<std::string>(v, "c");
return f;
}
};
} // toml
```
In this way, since the conversion function is introduced from out of the class,
you can add conversion between `toml::value` and classes defined in another library.
Note that you cannot implement both of the functions because the overload
resolution of `toml::get` become ambiguous.
----
The opposite direction is also supported in a similar way. You can directly
pass your type to `toml::value`'s constructor by introducing `into_iter` or
`toml::into<T>`.
```cpp
namespace ext
{
struct foo
{
int a;
double b;
std::string c;
toml::table into_toml() const // you need to mark it const.
{
return toml::table{{"a", this->a}, {"b", this->b}, {"c", this->c}};
}
};
} // ext
ext::foo f{42, 3.14, "foobar"};
toml::value v(f);
```
The definition of `toml::into<ext::foo>` is similar to `from_toml()`.
```cpp
namespace ext
{
struct foo
{
int a;
double b;
std::string c;
};
} // ext
namespace toml
{
template<>
struct into<ext::foo>
{
toml::table into_toml(const ext::foo& v)
{
return toml::table{{"a", this->a}, {"b", this->b}, {"c", this->c}};
}
};
} // toml
ext::foo f{42, 3.14, "foobar"};
toml::value v(f);
```
Any type that can be converted to `toml::value`, e.g. `toml::table`, `toml::array`,
is okay to return from `into_toml`.
### visiting toml::value
TOML v2.1.0+ provides `toml::visit` to apply a function to `toml::value` in the

1
tests/CMakeLists.txt
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@@ -29,6 +29,7 @@ set(TEST_NAMES
test_parse_unicode
test_error_detection
test_format_error
test_extended_conversions
)
CHECK_CXX_COMPILER_FLAG("-Wall" COMPILER_SUPPORTS_WALL)

116
tests/test_extended_conversions.cpp Normal file
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@@ -0,0 +1,116 @@
#define BOOST_TEST_MODULE "test_extended_conversions"
#ifdef UNITTEST_FRAMEWORK_LIBRARY_EXIST
#include <boost/test/unit_test.hpp>
#else
#define BOOST_TEST_NO_LIB
#include <boost/test/included/unit_test.hpp>
#endif
#include <toml.hpp>
namespace extlib
{
struct foo
{
int a;
std::string b;
};
struct bar
{
int a;
std::string b;
void from_toml(const toml::value& v)
{
this->a = toml::find<int>(v, "a");
this->b = toml::find<std::string>(v, "b");
return ;
}
toml::table into_toml() const
{
return toml::table{{"a", this->a}, {"b", this->b}};
}
};
} // extlib
namespace toml
{
template<>
struct from<extlib::foo>
{
static extlib::foo from_toml(const toml::value& v)
{
return extlib::foo{toml::find<int>(v, "a"), toml::find<std::string>(v, "b")};
}
};
template<>
struct into<extlib::foo>
{
static toml::table into_toml(const extlib::foo& f)
{
return toml::table{{"a", f.a}, {"b", f.b}};
}
};
} // toml
BOOST_AUTO_TEST_CASE(test_conversion_by_member_methods)
{
const toml::value v{{"a", 42}, {"b", "baz"}};
const auto foo = toml::get<extlib::foo>(v);
BOOST_CHECK_EQUAL(foo.a, 42);
BOOST_CHECK_EQUAL(foo.b, "baz");
const toml::value v2(foo);
BOOST_CHECK_EQUAL(v, v2);
}
BOOST_AUTO_TEST_CASE(test_conversion_by_specialization)
{
const toml::value v{{"a", 42}, {"b", "baz"}};
const auto bar = toml::get<extlib::bar>(v);
BOOST_CHECK_EQUAL(bar.a, 42);
BOOST_CHECK_EQUAL(bar.b, "baz");
const toml::value v2(bar);
BOOST_CHECK_EQUAL(v, v2);
}
BOOST_AUTO_TEST_CASE(test_recursive_conversion)
{
const toml::value v{
toml::table{{"a", 42}, {"b", "baz"}},
toml::table{{"a", 43}, {"b", "qux"}},
toml::table{{"a", 44}, {"b", "quux"}},
toml::table{{"a", 45}, {"b", "foobar"}},
};
const auto foos = toml::get<std::vector<extlib::foo>>(v);
BOOST_CHECK_EQUAL(foos.size() , 4ul);
BOOST_CHECK_EQUAL(foos.at(0).a , 42);
BOOST_CHECK_EQUAL(foos.at(1).a , 43);
BOOST_CHECK_EQUAL(foos.at(2).a , 44);
BOOST_CHECK_EQUAL(foos.at(3).a , 45);
BOOST_CHECK_EQUAL(foos.at(0).b , "baz");
BOOST_CHECK_EQUAL(foos.at(1).b , "qux");
BOOST_CHECK_EQUAL(foos.at(2).b , "quux");
BOOST_CHECK_EQUAL(foos.at(3).b , "foobar");
const auto bars = toml::get<std::vector<extlib::bar>>(v);
BOOST_CHECK_EQUAL(bars.size() , 4ul);
BOOST_CHECK_EQUAL(bars.at(0).a , 42);
BOOST_CHECK_EQUAL(bars.at(1).a , 43);
BOOST_CHECK_EQUAL(bars.at(2).a , 44);
BOOST_CHECK_EQUAL(bars.at(3).a , 45);
BOOST_CHECK_EQUAL(bars.at(0).b , "baz");
BOOST_CHECK_EQUAL(bars.at(1).b , "qux");
BOOST_CHECK_EQUAL(bars.at(2).b , "quux");
BOOST_CHECK_EQUAL(bars.at(3).b , "foobar");
}

20
toml/from.hpp Normal file
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@@ -0,0 +1,20 @@
// Copyright Toru Niina 2019.
// Distributed under the MIT License.
#ifndef TOML11_FROM_HPP
#define TOML11_FROM_HPP
#include "traits.hpp"
namespace toml
{
template<typename T>
struct from;
// {
// static T from_toml(const toml::value& v)
// {
// // User-defined conversions ...
// }
// };
} // toml
#endif // TOML11_FROM_HPP

38
toml/get.hpp
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@@ -2,6 +2,7 @@
// Distributed under the MIT License.
#ifndef TOML11_GET_HPP
#define TOML11_GET_HPP
#include "from.hpp"
#include "result.hpp"
#include "value.hpp"
#include <algorithm>
@@ -173,6 +174,20 @@ template<typename T, typename std::enable_if<detail::conjunction<
>::value, std::nullptr_t>::type = nullptr>
T get(const toml::value& v);
template<typename T, typename std::enable_if<detail::conjunction<
detail::negation<detail::is_exact_toml_type<T>>, // not a toml::value
detail::has_from_toml_method<T>, // but has from_toml(toml::value) memfn
std::is_default_constructible<T> // and default constructible
>::value, std::nullptr_t>::type = nullptr>
T get(const toml::value& v);
template<typename T, typename std::enable_if<detail::conjunction<
detail::negation<detail::is_exact_toml_type<T>> // not a toml::value
>::value, std::nullptr_t>::type = nullptr,
std::size_t = sizeof(::toml::from<T>) // and has from<T> specialization
>
T get(const toml::value& v);
// ============================================================================
// array-like types; most likely STL container, like std::vector, etc.
@@ -297,6 +312,29 @@ T get(const toml::value& v)
return map;
}
// ============================================================================
// user-defined, but compatible types.
template<typename T, typename std::enable_if<detail::conjunction<
detail::negation<detail::is_exact_toml_type<T>>, // not a toml::value
detail::has_from_toml_method<T>, // but has from_toml(toml::value) memfn
std::is_default_constructible<T> // and default constructible
>::value, std::nullptr_t>::type>
T get(const toml::value& v)
{
T ud;
ud.from_toml(v);
return ud;
}
template<typename T, typename std::enable_if<detail::conjunction<
detail::negation<detail::is_exact_toml_type<T>> // not a toml::value
>::value, std::nullptr_t>::type, std::size_t> // and has from<T>
T get(const toml::value& v)
{
return ::toml::from<T>::from_toml(v);
}
// ============================================================================
// find and get

20
toml/into.hpp Normal file
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@@ -0,0 +1,20 @@
// Copyright Toru Niina 2019.
// Distributed under the MIT License.
#ifndef TOML11_INTO_HPP
#define TOML11_INTO_HPP
#include "traits.hpp"
namespace toml
{
template<typename T>
struct into;
// {
// static toml::value into_toml(const T& user_defined_type)
// {
// // User-defined conversions ...
// }
// };
} // toml
#endif // TOML11_INTO_HPP

27
toml/traits.hpp
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@@ -9,6 +9,9 @@
namespace toml
{
class value; // forward decl
namespace detail
{
@@ -45,6 +48,22 @@ struct has_resize_method_impl
template<typename T> static std::false_type check(...);
};
struct has_from_toml_method_impl
{
template<typename T>
static std::true_type check(
decltype(std::declval<T>().from_toml(std::declval<::toml::value>()))*);
template<typename T>
static std::false_type check(...);
};
struct has_into_toml_method_impl
{
template<typename T>
static std::true_type check(decltype(std::declval<T>().into_toml())*);
template<typename T>
static std::false_type check(...);
};
/// Intel C++ compiler can not use decltype in parent class declaration, here
/// is a hack to work around it. https://stackoverflow.com/a/23953090/4692076
#ifdef __INTEL_COMPILER
@@ -62,6 +81,14 @@ struct has_mapped_type : decltype(has_mapped_type_impl::check<T>(nullptr)){};
template<typename T>
struct has_resize_method : decltype(has_resize_method_impl::check<T>(nullptr)){};
template<typename T>
struct has_from_toml_method
: decltype(has_from_toml_method_impl::check<T>(nullptr)){};
template<typename T>
struct has_into_toml_method
: decltype(has_into_toml_method_impl::check<T>(nullptr)){};
#ifdef __INTEL_COMPILER
#undef decltype(...)
#endif

41
toml/value.hpp
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@@ -3,6 +3,7 @@
#ifndef TOML11_VALUE_HPP
#define TOML11_VALUE_HPP
#include "traits.hpp"
#include "into.hpp"
#include "utility.hpp"
#include "exception.hpp"
#include "storage.hpp"
@@ -533,6 +534,46 @@ class value
return *this;
}
// user-defined =========================================================
// convert using into_toml() method -------------------------------------
template<typename T, typename std::enable_if<detail::conjunction<
detail::negation<detail::is_exact_toml_type<T>>, // not a toml::value
detail::has_into_toml_method<T> // but has `into_toml` method
>::value, std::nullptr_t>::type = nullptr>
value(const T& ud): value(ud.into_toml()) {}
template<typename T, typename std::enable_if<detail::conjunction<
detail::negation<detail::is_exact_toml_type<T>>, // not a toml::value
detail::has_into_toml_method<T> // but has `into_toml` method
>::value, std::nullptr_t>::type = nullptr>
value& operator=(const T& ud)
{
*this = ud.into_toml();
return *this;
}
// convert using into<T> struct -----------------------------------------
template<typename T, typename std::enable_if<
detail::negation<detail::is_exact_toml_type<T>>::value,
std::nullptr_t>::type = nullptr,
std::size_t S = sizeof(::toml::into<T>)>
value(const T& ud): value(::toml::into<T>::into_toml(ud)) {}
template<typename T, typename std::enable_if<
detail::negation<detail::is_exact_toml_type<T>>::value,
std::nullptr_t>::type = nullptr,
std::size_t S = sizeof(::toml::into<T>)>
value& operator=(const T& ud)
{
*this = ::toml::into<T>::into_toml(ud);
return *this;
}
// type checking and casting ============================================
template<typename T>
bool is() const noexcept {return value_traits<T>::type_index == this->type_;}
bool is(value_t t) const noexcept {return t == this->type_;}