Tag: Components

Using Autofac With Unity3D

Autofac With Unity

Why Consider Using Autofac With Unity3D?

I think using a dependency injection framework is really valuable when you’re building a complex application, and in my opinion, a game built in Unity is a great example of this. Using Autofac with Unity3D doesn’t need to be a special case. I wrote a primer for using Autofac, and in it I discuss reasons why it’s valuable and some of the reasons you’d consider switching to using a dependency container framework. Now it doesn’t need to be Autofac, but I love the API and the usability, so that’s my weapon of choice.

Building a game can result in many complex systems working together. Not only that, if you intend to build many games it’s a great opportunity to refactor code into different libraries for re-usability. If we’re practicing writing good code using constructor dependency passing with interfaces, then things really start to line up in favour of using a dependency injection framework.

Getting Set Up

At the end of my autofac primer article, I provided a link to the Nuget package for Autofac. You’ll notice that there’s a version dependency for .NET 4.5, so if you’re not sure how to get Unity3D working with .NET 4.5, you’ll want to check this other article of mine. It’s very simple, so don’t worry!

Unity3D, at the time of writing this and using version 2018.1.1f1, there’s no native Nuget package support. I haven’t spent too much time investigating alternatives, but not to worry. I’ll explain a quick work around. The TL;DR is that we need the binaries from the Nuget package to be loaded up by Unity3D and we’ll miss out on the Nuget-y-ness for now. Not a huge deal since we’ll still have Autofac support!

  • Start a new Visual Studio C# project
    • Ensure that the .NET framework is at least 4.5 and more specifically, the version of .NET that you’d like to use in your Unity3D project
  • Open up the Nuget package manager in Visual Studio
  • Search for Autofac online in the package manager (it should be the same one I referred to above!)
  • Add this package to your visual studio project
  • Compile this visual studio project
  • Assuming you built in debug, go to the output folder (which is in bindebug if you didn’t change anything from default)
  • In the output folder, you’ll find “Autofac.dll”
  • You’ll want to add this into your Unity3D project’s “Assets” folder
    • I like nice folder hierarchies, so I’d suggest making a subfolder inside of “Assets” called “Third Party” or “Dependencies”… Something that’s obvious for what it means
    • Drop in the Autofac.dll file into there
  • Unity3D will add a corresponding *.meta file to go along with this

Great! We’re almost there. If you want to test it out, open up a script from Unity3D. This will launch a new Visual Studio instance if you haven’t opened up one for your Unity project yet. At the very top of your file you should be able to type:

using Autofac;

And the namespace should resolve! If not, sometimes this takes Unity3D a refresh operation to regenerate the project file on disc, so if you switch to Unity3D again and it starts doing some processing, switching back to Visual Studio might resolve this.

Using Autofac With Unity3D

Up until this point, we’ve proven we can reference Autofac. I’m not going to explain all the ins and outs for how you’ll want to organize your Autofac initialization in this post, but we can walk through a quick example!

  • Pick a game object on your scene
  • Add a new C# script to it
    • Call it whatever you’d like, but make sure you know how to open it
  • … now go open it in Visual Studio 🙂
  • We should have a method in there called Start()
    • If not, feel free to add it:
    • private void Start()
      {
        // TODO: we'll add stuff here
      }
  • Let’s use this code to make a new class that you can put inside the same script file for now:
    • public sealed class MyAutofacObject
      {
      
        public MyAutofacObject()
        {
          Debug.Log("Constructor for our object!");
        }
      
        public void DoThing()
        {
          Debug.Log("Test!");
        }
      }
  • Inside this start method, let’s try doing something VERY simple to prove Autofac works!
    • var containerBuilder = new Autofac.ContainerBuilder();
      containerBuilder.RegisterType<MyAutofacObject>().SingleInstance();
      
      var container = containerBuilder.Build()
      var instance = container.Resolve<MyAutofacObject>();
      
      instance.DoThing();

Now if we run our game, here’s what should happen:

  • The script attached to the game object should run
  • The Start() method on the script should be the first thing that goes
  • The code we added should:
    • Make a new ContainerBuilder
    • Register our MyAutofacObject type as a single instance
    • Build the container
    • Resolve an instance of our type
    • Log out a message saying it’s in the constructor
    • Log out a message that says Test!

And voila! It’s simple, but it should demonstrate that Autofac is working!

Next Steps

This is a very contrived example of using Autofac with Unity3D. It proves that the code can be run, but it doesn’t do too much that’s useful. There are going to be many considerations you’ll need to make for how you want to organize your dependencies, register your classes/interfaces, and so on.

I’ll continue to add into this Unity3D series of posts, but let me know what else you’d like to know about using Autofac with Unity3D! I’d be happy to try and answer, or even create an article to help explain.

Thanks!


Part 1 – Exploring Graphs and Trees

Graphs and Trees - Delta State Algorithm

Graphs and Trees to Start

I was chatting with my colleague about generating maps for a 2D role playing game the other day after getting super excited explaining picking ProjectXyz back up and looking into Unity3D more. He was expressing interest in algorithms for procedural generation and storing data in trees or graphs as an optimal data structure for the scenario we were going over.

It stuck with me though. I’ve been putting a lot of thought into game state management and wanting to address it by using a generic layering/stacking approach. By that, I mean that I want to find a way to take base game state, allow mods or plugins to overlay their state, allow game patches to overlay their state, and then save game data to be overlaid on top of all of that. Conceptually, I believe I can create a generic system for doing this stacking of game data, which I’ll be referring to as my Delta State Algorithm, but I’ve been struggling with a starting point.

But the trees and graph concept stuck with me because the properties of trees and graphs that my colleague was referring to seemed to line up with how I envisioned this algorithm working. A graph or a tree just might be the right structure to represent this game state and the deltas between them, so I wanted to start mocking up some ideas.

A Map is a Game Object… And so is Everything Else?

Confusing subheader? You bet. But it’s because it was an odd realization.

I’ve been re-writing the same back end for an RPG for years now. Literally, it’s probably been at least 10 years that I’ve started, progressed, and scrapped such a game. But one thing I borrowed from Unity3D development was the idea of components and component-based design. I was far too married to object hierarchies, and these would eventually result in me having to refactor a TON of code. If you couple that with the fact I wasn’t using dependency injection properly (see this little primer article), it meant my refactoring efforts got to the point where it just made sense to start over.

So I was working with loading maps from TMX or Tiled map formats, and after getting these to load I was putting some thought into how I wanted to save/load my game objects. My game objects are essentially containers of components, and the containers have no properties at all. What does that mean in practice? My Actor/NPC game object class is the exact same class as an equippable item! It’s just “GameObject”. The difference between them is the variation in the components that I attach to them. In my mind, I figured I’d need some sort of hierarchical serialization paradigm where my game object would serialize itself, then the components would serialize themselves within that process, and if I could have components with components… You get the idea. But this could sort of be represented by a tree structure.

After the discussion with my colleague about trees and graph structures for maps, I connected some dots. Really the tiles and placed objects on a map were just… game objects as well. And that means that my thought process behind hierarchical serialization aligns well with some of the properties he was referring to for maps as graphs/trees. This suggests that “world state” for a game where everything is a “GameObject” with components attached to them (where some of those components can contain other GameObjects) could be represented by a graph or tree data structure

What About Tabulated and Listed Data Sets?

So we’ve come up with a starting point for “World Data” being represented by a graph. However, if we go back to my initial goal, I want plugins/mods/patches to be able to get applied to base “Game State” data.

What’s the difference between world and game state data?

These are just my terms so I should try and clarify. The world data is the data the player sees in the playable world. It’s the status of the objects and the maps they are interacting with. Game state data is the superset of this data and all of the other lookup data for loading content into the game. So this OTHER data includes things like the possible stats players and items can have, the types of monsters that can spawn (not the instances of the spawned monsters, because that’s the world state data), the possible dialog entries, etc… This type of data is really well represented in a relational database where we can create lists of data entries.

But if we take a step back, can’t that relational database content also be represented as a graph?

Could I have:

  • A node called “Stats” as a parent to a “Life” node that is a parent to a “StatRange” node, and “LocalizedNameResource” node?
  • A node called “BaseItems” as a parent to a “Sword” node that is a parent to a “DamageRange” node, “RequiredStats” node, and “EquippableSlots” node?
  • A node called “MonsterSpawns” as a parent to a “Skeleton” node that is a parent to…

You get the idea. I generally think about this data in a relational database paradigm (and perhaps it’s much faster to edit the data this way or look it up this way). However, if I can transform this data into the same type of graph structure I want to use for world state, then it means my delta state algorithm would work on not only world state data but also ALL game state data.

So Everything in the Graph? Always?

This is an important question, and I think one that without actually explicitly thinking about was causing me some headaches and keeping me from progressing down exploring more of my delta state algorithm.

I mentioned that some of the game state data feels better represented in a relational database. It might be much faster to add/remove or look them up when the data feels like it’s just a list of records when you contrast that with a graph. But why not have multiple storage mechanisms?

The delta state algorithm serves a very important goal: Layer deltas of data on top of a base set to get a new set.

That’s it though. So once I have that final transform of data that represents the new game state, who says I can’t transform it into a different format?

Maybe the world state is still better represented as a graph. So things like maps with tiles and game objects in the world still are super efficient to work with in graph form. Maybe things like dialog entries or definitions of player stats are better represented in a relational database… I could populate a database with the necessary data based on the graph data though. And the really cool part? A save game, which is probably the delta that changes the most, probably shouldn’t have the extra game state data in it (likely just has world state deltas represented). So… if a relational database is better suited for the remaining game state data, this could get generated and cached, and then only regenerated when different mods/plugins/patches are applied!

Concluding Thoughts

To summarize some of the major thoughts discussed in this article:

  • Game objects with components can be represented by nodes in a graph just like maps with tiles on them.
  • Other game state that feels better suited for relational databases can still be transformed into nodes in a graph for working with deltas.
  • Once a final game state is calculated (based on base state + deltas for mods/plugins/patches + delta for save game), data can be transformed back into the most suitable form to work with
  • Data does NOT have to exist in only one form! We can transform it as we need to work with it more effectively.

While this article was a bit of a brain dump, this the thought process that got the ball rolling for starting to design this delta state algorithm. In my next post in this series, I want to discuss a quick look at undo/redo approaches used in applications and how they might be similar (or different) to how the delta state algorithm might work.


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  • Nick Cosentino

    Nick Cosentino

    I work as a team lead of software engineering at Magnet Forensics (http://www.magnetforensics.com). I'm into powerlifting, bodybuilding, and blogging about leadership/development topics over at http://www.devleader.ca.

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