D structs are typically a value type (different variables are always different objects), as opposed to D's classes, which are always a reference type (different variables may refer to the same object). Sometimes, we want the struct that has reference semantics to ensure that assignment is cheap, for example.
To create a struct with reference semantics, we will execute the following steps:
Create a struct with a single data member that is itself a reference type, such as a pointer.
You may choose to use a private nested struct to hold the implementation, using
alias thisto forward methods automatically. The reference counted object in the previous chapter is a reference-type struct that uses this technique.Use the struct normally—you should not use the
refstorage class when passing it to functions.