Modding Tutorials/Custom Comp Classes

Creating a custom comp class is a convenient way to add new functionality to RimWorld.

Prerequisites

You need to have set up your editor and environment
You need to know how to write custom code
You should probably understand Defs at least somewhat.

def (xml) and C# structure

Setup, Defs, and Classes

You will have some custom def and it will have something like this:

Defs (xml)

 <ThingDef ...>
   ...
   ...
   <comps>
     <li Class="MyNamespace.MyCompProperties">
       <myCustomCompProperty>some value</myCustomCompProperty>
       <mySecondCompProp>4</mySecondCompProp>
     </li>
     <li>
       <!-- this is kind of like <tag>MN.MyCustomTag</tag>:-->
       <compClass>MyNamespace.MyCustomThingComp</compClass>
     </li>
   </comps>
 </ThingDef>

C#

 namespace MyNamespace // For example, LWM.ModName - by using your 
                       //   handle/name/etc, you almost certainly guarantee uniqueness
 {
 //////////// <<nowiki>li</nowiki Class="MyNamespace.MyCompProperties"> ////////////
 public class MyCompProperties : CompProperties // Name this as you wish, of course
 {
   public Properties() {
     this.compClass = typeof(MyNamespace.MyLinkedCompThing); // rename as appropriate
   }
   public string myCustomCompProperty; // Name matches def, of course
   public int mySecondCompProp = 1; // Can set default values
 }
 
 // this ThingComp is used to actually access the comp property defined above
 // this is not "<compClass>MyNamespace.MyCustomThingComp</compClass>"
 public class MyLinkedCompThing : ThingComp
 {
   public string myCustomCompProperty
   {
     get
     {
       return ((MyCompProperties)this.props).myCustomCompProperty;
     }
   }
   public int mySecondCompProperty // Have to get all the names right
   { get  { return ((MyCompProperties)this.props).mySecondCompProperty; } } //etc
 }
 //////////// <compClass>MyNamespace.MyCustomThingComp</compClass> ////////////
 public class MyCustomThingComp : ThingComp
 {
   public override void CompTick()
   {
     // do stuff
   }
   public override void CompTickRare() //etc
   public override ... // Check out Verse/ThingComp.cs for more ideas
 }
 } // end MyNamespace

Accessing your Comps

Just setting up your custom comps doesn't do you a lot of good if you can't access them!

To do

Cautions, traps, etc

If you have the same comp in an abstract def and attempt to redefine it in a child def, it will get counted twice. It's possible to get around this in the code, if you want to have default comps:

 public class MyLinkedCompThing : ThingComp
 {
   public string myCustomCompProperty //etc
   
   public override void Initialize (CompProperties props) {
     base.Initialize(props);
     // Remove duplicate entries and ensure the last entry is the only one left
     //   This allows a default abstract def with the comp
     //   and child def to change the comp value:
     CompDeepStorage[] list = this.parent.GetComps<CompDeepStorage>().ToArray();
     // Remove everything but the last entry; harmless if only one entry:
     for (var i = 0; i < list.Length-1; i++)
     {
       this.parent.AllComps.Remove(list[i]);
     }
   }
 
 ///etc
 }