nameof_module/doc/limitations.md
2019-10-03 18:39:46 +05:00

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# Nameof
* If argument does not have name, occurs the compilation error `"Expression does not have a name."`.
# Nameof Type
* To check is nameof_type supported compiler use macro `NAMEOF_TYPE_SUPPORTED` or constexpr constant `nameof::is_nameof_type_supported`.
* This library uses a compiler-specific hack (based on `__PRETTY_FUNCTION__` / `__FUNCSIG__`), which works on Clang >= 5, MSVC >= 15.3 and GCC >= 7.
* Nameof type returns compiler-specific type name.
* If argument does not have name, occurs the compilation error `"Expression does not have a name."`.
# Nameof Enum
* To check is nameof_enum supported compiler use macro `NAMEOF_ENUM_SUPPORTED` or constexpr constant `nameof::is_nameof_enum_supported`.
* This library uses a compiler-specific hack (based on `__PRETTY_FUNCTION__` / `__FUNCSIG__`), which works on Clang >= 5, MSVC >= 15.3 and GCC >= 9.
* Enum can't reflect if the enum is a forward declaration.
* Enum value must be in range `[MAGIC_ENUM_RANGE_MIN, MAGIC_ENUM_RANGE_MAX]`. By default `MAGIC_ENUM_RANGE_MIN = -128`, `MAGIC_ENUM_RANGE_MAX = 128`.
* If need another range for all enum types by default, redefine the macro `MAGIC_ENUM_RANGE_MIN` and `MAGIC_ENUM_RANGE_MAX`.
```cpp
#define MAGIC_ENUM_RANGE_MIN 0
#define MAGIC_ENUM_RANGE_MAX 256
#include <magic_enum.hpp>
```
* If need another range for specific enum type, add specialization `enum_range` for necessary enum type.
```cpp
#include <magic_enum.hpp>
enum number { one = 100, two = 200, three = 300 };
namespace magic_enum {
template <>
struct enum_range<number> {
static constexpr int min = 100;
static constexpr int max = 300;
};
}
```
* `magic_enum` obtains the first defined value enums, and won't work if value are aliased.
```cpp
enum ShapeKind {
ConvexBegin = 0,
Box = 0, // Won't work.
Sphere = 1,
ConvexEnd = 2,
Donut = 2, // Won't work too.
Banana = 3,
COUNT = 4,
};
// magic_enum::enum_cast<ShapeKind>("Box") -> std::nullopt
// magic_enum::enum_name(ShapeKind::Box) -> "ConvexBegin"
```
Work around the issue:
```cpp
enum ShapeKind {
// Convex shapes, see ConvexBegin and ConvexEnd below.
Box = 0,
Sphere = 1,
// Non-convex shapes.
Donut = 2,
Banana = 3,
COUNT = Banana + 1,
// Non-reflected aliases.
ConvexBegin = Box,
ConvexEnd = Sphere + 1,
};
// magic_enum::enum_cast<ShapeKind>("Box") -> ShapeKind::Box
// magic_enum::enum_name(ShapeKind::Box) -> "Box"
// Non-reflected aliases.
// magic_enum::enum_cast<ShapeKind>("ConvexBegin") -> std::nullopt
// magic_enum::enum_name(ShapeKind::ConvexBegin) -> "Box"
```