SSR - Super Simple Reflection

An easy-to-use reflection realized under C++14. Only minimum modification is needed for existed codes.

Introduction

What's good about SSR?

1. Users can use a name to create an instance of a class without knowing its type.

2. Users can get "reflected" variables of a class, iterate over them, and get their names, types, and values.

3. You can bind other reflection systems with it - Protobuf reflection, for example.

Usage

Definition

Only one line of code is needed to mark the class as using reflection.

// in .h file
class ReflectA {
 public:
  USE_REFLECTION_CLASS();
  
  // What is desired to be caught by reflection
  int32_t a_;
  // What is NOT desired to be caught by reflection
  int32_t b_;
};

In the realization .cc file that included the previous .h file, one line of code is also needed to declare its descriptor as well as variables to be reflected.

// in .cc file
// First parameter is typename of class, followed by name of reflected variables
ADD_REFLECTION_CLASS_MEMBER(ReflectA, a_);

Actual Use

As the class has been reflected, you can get all info you need through descriptor, or create new instances by type name.

// Scenario1: an instance existed
ReflectA a;
auto* desc_a = prophet::reflection::DescriptorAccessor<ReflectA>::Get();
desc_a->GetFieldName(0); // "a_"
desc_a->MutableFieldValueById(&a, 0); // a void* ptr to a_ in a
desc_a->MutableFieldValueByName(&a, "a_"); // a void* ptr to a_ in a

// Scenario2: no instance existed
auto* b = NEW_CLASS_PTR("ReflectA");
auto* desc_b = DESC("ReflectA"); // same as desc_a in scenario 1
desc_b->MutableFieldValueById(b, 0); // a void* ptr to a_ in b

Find deriviation

For OOP, polymorphism is an important feature. If you need to find descriptor of derived class pointed by a base pointer, here's a simple example on how to do so.

class BaseClass {
 public:
  // DEFINE REFLECTIONS

  virtual std::string GetClassName() const { return class_name; }

 private:
  std::string class_name{"BaseClass"};
};

class DerivedClassA {
 public:
  // DEFINE REFLECTIONS

  virtual std::string GetClassName() override const { return class_name; }

 private:
  std::string class_name{"DerivedClassA"};
};

class DerivedClassB {
 public:
  // DEFINE REFLECTIONS

  virtual std::string GetClassName() override const { return class_name; }

 private:
  std::string class_name{"DerivedClassB"};
};

// When use
// Assume that we have a std::vector<BaseClass*> class_group
for (auto* class : class_group) {
  auto* class_desc = DESC(class->GetClassName());
}

// We are also providing RTTI-based methods and in-class methods
for (auto* class : class_group) {
  auto* class_desc = DESC_BY_BASE_PTR(class);
}

void ReflectA::Iterate() {
  auto* curr_desc = DESC_BY_THIS(this);
}

Supported Pre-defined types

Status	Pre-defined Types
✔️	int32_t
✔️	int64_t
✔️	float
✔️	double
✔️	bool
✔️	std::string
✔️	char
✔️	glm::vec3
✔️	glm::vec4
✔️	glm::mat3
✔️	glm::mat4
✔️	glm::quat
✔️	google::protobuf::Message

Supported containers and template types

Status	Containers
✔️	std::vector
✔️	std::map
✔️	std::unordered_map
✔️	std::set
✔️	std::unordered_set
❌	std::list
❌	std::deque
✔️	std::unique_ptr
✔️	std::shared_ptr
❌	std::pair