Type-Erasure in WTF

The goal of WTF is to have the user work with objects like wtf::Float, wtf::FloatBuffer and not say wtf::Float<double>, but at the same time ensure that operations are done in a type-safe manner. This is achieved through a pattern known as “type-erasure”. This page documents how we pull type-erasure off in WTF.

Terminology

Type-erasure involves three classes.

1. The “Interface” class. This is the class that the user interacts with. In WTF these are wtf::Float and wtf::Buffer.

2. The “Holder” class. This is an abstract base class that defines the interactions between the “Interface” class and the actual data. In WTF this is wtf::detail::FloatHolder and wtf::detail::BufferHolder.

3. The “Model” class. This is a class templated on the type of data being held. It derives from the “Holder” class and implements a model for data of type T. In WTF these are wtf::detail::FloatModel<T> and wtf::detail::BufferModel<T>.