Unity Game Optimization - Third Edition

foreach loops

The foreach loop keyword is a bit of a controversial issue in Unity development circles. It turns out that a lot of foreach loops implemented in Unity C# code will incur unnecessary heap memory allocations during these calls, as they allocate an Enumerator object as a class on the heap, instead of a struct on the stack. It all depends on the given collection's implementation of the GetEnumerator() method.

Note that it is safe to use foreach loops on typical arrays. The Mono compiler secretly converts foreach over arrays into simple for loops.

Since Unity 2018.1, Unity uses an upgraded Mono runtime (4.0.30319) and some compiler fixes many of the previous issues with foreach. As a consequence, foreach is no more a big issue in ...