Resolved How do you create a Dictionary with Type as the key?

I tried this and it doesn't work:


When I hover over the red it says:


Why is a type not a valid key if the Dictionary takes Type as a key?

Edit:
Nvm I did typeof(Fish) and it worked.
I swear I spent like 20 mins trying to fix this and I figured it out 3 mins after I post this.

 

System.Type

is a class that belongs to the reflection system of C#. This class "describes" the structure of another type. What you try to store in the dictionary is a class itself which doesn't make sense to the compiler. A class is a concept and not a value that you could store somewhere. You need to use the typeof operator to get the System.Type object of a certain class.

typeof(Fish)

instead of

Fish

 

Just be careful whenever you're anywhere near serialization and Type. A type reference is really only good for the current application memory space and loaded scripts. If you save a Type, it does not save something that is guaranteed to work properly when you load it in the future, especially after assembly files change or with generics. You can as the Type itself to get a string that represents the type's name, full name, assembly full name, etc. Then you have [MovedFrom] attributes and other hacks. You can look for various solutions to this, usually people call it "SerializableType" or something like it. There's no real good plan here.

 

I don't imagine this to be a regular problem though as Unity can't serialise types? (Nor can it serialise dictionaries)

That said renaming/moving types does cause issues with

[SerializeReference]

, which is where the

[MovedFrom]

attribute comes into play.

 

Since we already sidestepped the question a bit, If you're looking for a generally serializable System.Type reference, I made such a wrapper about 10 years ago. It's still on my dropbox... I need to move it somewhere more sensible in the future ^^.

It uses a compact binary format which stores the type as a fully qualified string. Though it also does store generic arguments recursively. So it should support literally ANY concrete type. On top of that I also made a serializable MethodInfo which does exactly that. It uses the serializable type for the parent type of the method as well as for the arguments of the method in order to uniquely identify the method in case of overloads.

You barely would need that. Just like my attempt in storing coroutines to disk. It actually works, with some limitations. You can do some crazy things with reflection, but in the end you have to ask yourself if it's worth it and how easily it can break.