Here is the code.

int_f mod_CanCityBuildUnit(city_t theCity, int_t theUnit)
{
if (theUnit == UnitDB(UNIT_LEGION))
{
if(HasAdvance(theCity.owner, AdvanceDB(ADVANCE_MILITARISM)))
{
return 1; // can build this
}
else
{
return 0; // can't build this
}
}
if (theUnit == UnitDB(UNIT_HUNTER))
{
if(HasAdvance(theCity.owner, AdvanceDB(ADVANCE_WHEEL)))
{
return 1; // can build this
}
else
{
return 0; // can't build this
}
}
return 1; // can build all other units
}

This way, legion should be buildable only if the player has the techs militarism and iron working (iron working is used in the unit.txt with EnableAdvance, and militarism via SLIC).

Trouble is :
- Legion can appear in the buildable units list as soon as I discover Iron Working. But they do not appear every time ! ("random" behaviour every time you open the build list of the city). When I try to add the unit, it is not added in the list... Most of the time... If I click fast enough, I can add some legions in the lists (like 2 legions if I click 10 times...).

code:

---

int_f mod_CanCityBuildUnit(city_t theCity, int_t theUnit) {
city_t	tmpCity;			// added
int_t	tmpUnit;			// added
	tmpUnit = theUnit;		// added
	tmpCity = theCity;		// added

	if (tmpUnit == UnitDB(UNIT_LEGION)) {
		if(HasAdvance(tmpCity.owner, AdvanceDB(ADVANCE_MILITARISM))) {
			return 1; // can build this
		} else {
			return 0; // can't build this
		}
	}
	if (tmpUnit == UnitDB(UNIT_HUNTER)) {
		if(HasAdvance(tmpCity.owner, AdvanceDB(ADVANCE_WHEEL))) {
			return 1; // can build this
		} else {
			return 0; // can't build this
		}
	}
	return 1; // can build all other units
}

---

I think your problem might originate in the way you modified Locutus's original code. Try this:

code:
--------------------------------------------------------------------------------

int_f mod_CanCityBuildUnit(city_t theCity, int_t theUnit) { if (theUnit == UnitDB(UNIT_LEGION)) { if(HasAdvance(theCity.owner, AdvanceDB(ADVANCE_MILITARISM))&& HasAdvance(theCity.owner, AdvanceDB(ADVANCE_IRON_WORKING)) )
{ return 1; // can build this } else { return 0; // can't build this } } if (theUnit == UnitDB(UNIT_HUNTER)) { if(HasAdvance(theCity.owner, AdvanceDB(ADVANCE_WHEEL))&& HasAdvance(theCity.owner, AdvanceDB(ADVANCE_???)) )
{ return 1; // can build this } else { return 0; // can't build this } } return 1; // can build all other units}

--------------------------------------------------------------------------------

The '???' are for your other advance in this case. It's untested but with luck it should over-ride the advance prerequisites in Units.txt.

Add separate techs for units that require two or more techs to build. Grant these techs automatically using SLIC once the required two plus techs have been discovered so the player doesn't need to research them... like:
trigger 'GiveTech' when (HasAdvance(player,ID_ADVANCE_1) && HasAdvance(player, ID_ADVANCE_2))
{
//code here
}

That's CTP1 syntax, but the concept will do the trick. It'll also work for civ-specific units, when each civ has a tech corresponding to it's civ, like ADVANCE_ROMAN, etc, and each unit needs a combination of advances, like ADVANCE_JAPANESE and ADVANCE_IRON_WORKING for the samurai, etc.