Disabling Parts of External Functions
Introduction
Sometimes you need to use a game function, but with some parts disabled. For example, Clan.OnCompanionAdded not only adds a hero to the clan companion list,
but also adds him to the hero list.
public void OnCompanionAdded(Hero companion)
{
_companionsCache.Add(companion);
OnHeroAdded(companion); // Function that adds the hero to the hero list
}
But what if we don’t want this? One way you could just copy the function and get the maintenance burden of it.
Another way would be to use a Harmony reverse patch. You can get a copy of the function and manually manipulate the IL code to disable the OnHeroAdded call.
We suggest a higher level approach, based on using scopes and IDisposable.
Scoped Disabling Technique
using allows us to create a scope. While this scope is active, we use a harmony patch that disables the execution of the unwanted function.
using (new AddCompanionActionHandler())
{
// Within this scope any call to `OnHeroAdded` will be skipped.
oldLeader.Clan.OnCompanionAdded(oldLeader);
}
The Harmony patch
public class AddCompanionActionHandler : IDisposable
{
public AddCompanionActionHandler() => AddCompanionActionPatch.SkipChange = true;
public void Dispose() => AddCompanionActionPatch.SkipChange = false;
}
internal class AddCompanionActionPatch
{
internal static bool SkipChange = false;
public static bool Enable(Harmony harmony)
{
return true &
harmony.TryPatch(
original: AccessTools2.Method(typeof(Clan), "OnHeroAdded"),
prefix: AccessTools2.Method(typeof(AddCompanionActionPatch), nameof(Prefix)));
}
private static bool Prefix() => !SkipChange;
}