Unity and Reflection – Optimising Memory using Caching on iOS

Introduction

I really love reflection. Reflection is a technique used for obtaining type information at run-time. It’s not only that, with reflection is possible to examine and change information of objects, to generate (technically to emit IL) new classes, methods and so on still at runtime. It’s a powerful technique but it is known, under certain circumstances, for being slow. If you are a game developer and you are targeting mobile devices (iOS or Android for instance) using Unity, you definitely want to preserve your memory and save precious clock cycles. Moreover, with AOT (Ahead of Time compilation)  IL cannot be emitted at run-time as it is pre-generated at compile time. Therefore a large part of reflection, e.g. expression trees, anonymous types etc., is just not available.

The Problem

Recently I have worked on a dynamic prefab serializer and I needed to use reflection to retrieve types from their string representations. In general to retrieve a type in C# you have three options:

  • typeof(MyClass), which is an operator to obtain a type known at compile-time.
  • GetType() is a method you call on individual objects, to get the execution-time type of the object.
  • Type.GetType(“Namespace.MyClass, MyAssembly”) gives you a type from its string representation at runtime.

typeof is converted into a constant at compile time and GetType  returns a reference to the run-time type of your object. But what about Type.GetType(string)???

Read More