Type Erasure

This pattern was inspired by Klaus Iglberger's presentations:

When To Use

Type Erasure decouples operations from types by using external polymorphism. Allowing for easy addition of new types.

General:

Easy to add types over adding operations.
Types do not have dependency on operations.
Restricts the operations to the public interface of the types.
Enables a value semantic interface to promote simple natural code.

Features

Create a Type:

class TypeA
{
public:
};

Create an Operation:

// Free function to handle TypeA
void OperationA(TypeA& type)
{
}

// Add OperationA to Type::TypeConcept. See typeerasuretype.h
class TypeConcept
{
public:
    ...
    virtual void OperationA() = 0;
};

// Call OperationA within Type::TypeModel. See typeerasuretype.h
template<class TType>
class TypeModel final : public TypeConcept
{
public:
    ...
    void OperationA() override
    {
        ::OperationA(m_Type); // Call the free function that handles this Operation/TType combination.
    }

    TType m_Type{};
};

Call an Operation:

using Types = std::vector<Type>;

Types types{}
types.emplace_back(TypeA{});
for(Type& type : types)
{
    type.OperationA();
}

Setup

This repository uses the .sln/.proj files created by Visual Studio 2022 Community Edition. Using MSVC compiler, Preview version(C++23 Preview).

Catch2

The examples for how to use the pattern are written as Unit Tests.

Launching the program in Debug or Release will run the Unit Tests.

Alternative: Installing the Test Adapter for Catch2 Visual Studio extension enables running the Unit Tests via the Test Explorer Window. Setup the Test Explorer to use the project's .runsettings file.

vcpkg

This repository uses vcpkg in manifest mode for it's dependencies. To interact with vcpkg, open a Developer PowerShell (View -> Terminal).

To setup vcpkg, install it via the Visual Studio installer. To enable/disable it run these commands from the Developer PowerShell:

vcpkg integrate install
vcpkg integrate remove

To add additional dependencies run:

vcpkg add port [dependency name]

To update the version of a dependency modify the overrides section of vcpkg.json.

To create a clean vcpkg.json and vcpkg-configuration.json file run:

vcpkg new --application

TODO

Implementation
Unit Tests
Benchmarks