pimplike

Pimplike is a term used to describe patterns or practices that resemble the Pimpl (pointer to implementation) idiom, in which a class presents a public API while delegating most of its data and behavior to a separate private object accessed through an opaque pointer or handle. The objective is to separate interface from implementation, thereby reducing coupling between a library’s headers and its clients, and enabling change of private details without breaking dependent code. While closely related to the classic Pimpl idiom in C++, pimplike can be used to describe similar approaches in other languages or contexts where an opaque private implementation is hidden behind a public surface.

Typical structure involves a public class that forward-declares or otherwise references a private implementation type, often stored as a pointer or smart pointer. The actual implementation class is defined in a source file, not in the public header, so changes to private data members or helper methods do not force recompilation of users’ code. The public methods act as wrappers, delegating work to the private implementation. This pattern is frequently accompanied by careful management of construction, destruction, and copying or moving semantics to maintain proper ownership and resource management.

Benefits of pimplike patterns include reduced header-file dependencies, faster compilation for large projects, and improved ABI (application binary interface) stability, which makes it easier to evolve private details without breaking binary interfaces. They can also enhance encapsulation by hiding implementation details more completely.

Drawbacks include the overhead of an extra level of indirection, potential performance costs, and increased complexity in memory management and debugging. Copying or moving the public object usually requires explicit handling of the underlying implementation, which can complicate code and testing. Pimplike approaches are most common in library design where API stability and compilation performance are priorities.