Mirror (programming)

In Computer programming, a Mirror is a Reflection mechanism that is completely decoupled from the object whose structure is being introspected. This is as opposed to traditional reflection, for example in Java, where one introspects an object using methods from the object itself (e.g. getClass()).

Mirrors adhere to the qualities of encapsulation, stratification, and ontological correspondence. [1]

Benefits

Decoupling the reflection mechanism from the objects themselves allows for a few benefits:

• The object's interface isn't polluted, so there is no danger of breaking reflection by overriding a reflective method.
• You can have different mirror systems.
• The mirror system can be removed entirely (potentially allowing for optimizations).
• Mirror systems can operate on remote code, since it isn't coupled with a particular machine.

Languages that use Mirrors

• Dart, via its reflect function.
• Scala

References

• Paper on Meta-level Facilities of Object-Oriented Programming languages by Gilad Bracha and David Ungar