Compiler Basics

Use the injects, shims, or merges keyword (see the injects.py, shims.py, and merges.py files).

in my repo folder I have BalancePS40.uc, which starts with this

class BalancePS40 injects WeaponHideAGun;

this tells the compiler to create these in the output folder

WeaponHideAGunBase.uc

// === was WeaponHideAGun ===
class WeaponHideAGunBase extends DeusExWeapon;

and WeaponHideAGun.uc

// === was BalancePS40 ===
class WeaponHideAGun extends WeaponHideAGunBase;

shims is similar to injects, except instead of the new file taking the place of the old file, the old file keeps its name but all of the subclasses get modified for the new parent. So if you do class FixScriptedPawn shims ScriptedPawn; then it becomes class FixScriptedPawn extends ScriptedPawn; and the old subclasses of ScriptedPawn will now be changed to say extends FixScriptedPawn; This also supports chains.

The merges keyword appends your code to the original file, any functions you overwrite will have the original function renamed to have an underscore in the front, for example the game requires DeusExLevelInfo to inherit directly from Info so we can't use injects for it, we instead use merges

from my repo folder LevelInfo.uc

class DXRLevelInfo merges DeusExLevelInfo;

function SpawnScript()
{
    local DXRando dxr;
    local bool bFound;

    bFound = False;
    foreach AllActors(class'DXRando', dxr)
        bFound = True;
    
    if (!bFound) {
        dxr = Spawn(class'DXRando');
        dxr.SetdxInfo(Self);
    }

    _SpawnScript();
}

this results in the original SpawnScript function in DeusExLevelInfo to be renamed to _SpawnScript, you can see my code calling that function, and then the compiler adds this to the bottom of the DeusExLevelInfo.uc file

// === merged from .//DXRLevelInfo

/* class DXRLevelInfo merges DeusExLevelInfo; */

function SpawnScript()
{
    local DXRando dxr;
    local bool bFound;

    bFound = False;
    foreach AllActors(class'DXRando', dxr)
        bFound = True;
    
    if (!bFound) {
        dxr = Spawn(class'DXRando');
        dxr.SetdxInfo(Self);
    }

    _SpawnScript();
}