Skip to content

Instantly share code, notes, and snippets.

Roope Kangas muhmi

View GitHub Profile
cobbpg /
Last active May 8, 2020
Unity hotswapping notes

Unity hotswapping notes

Unity has built-in support for hotswapping, which is a huge productivity booster. This feature works not only with graphics assets like bitmaps and meshes, but also with code: if you edit the source and save it, the editor will save the state of the running game, compile and load the new code, then load the saved state and continue where it left off. Unfortunately, this feature is very easy to break, and most available 3rd party plugins have little regard for it.

It looks like there’s a lot of confusion about hotswapping in Unity, and many developers are not even aware of its existence – which is no wonder if their only experience is seeing lots of errors on the console when they forget to stop the game before recompiling... This document is an attempt to clear up some of this confusion.

Nota bene, I’m not a Unity developer, so everything below is based on blog posts and experimentation. Corrections are most welcome!

The basic flow of hotswapping

Lee-R / lithash.cpp
Created Oct 5, 2012
C++11 compile-time hash of literal strings.
View lithash.cpp
#include <cstdint>
namespace detail
// FNV-1a 32bit hashing algorithm.
constexpr std::uint32_t fnv1a_32(char const* s, std::size_t count)
return ((count ? fnv1a_32(s, count - 1) : 2166136261u) ^ s[count]) * 16777619u;
} // namespace detail
You can’t perform that action at this time.