Sort table in lua as multible groups - sorting

Question

I need to sort a list _rolls to have both the users rolls and ranks taken into considerations.
_rolls = {
{Username="User1", Roll=50, RankPrio=1},
{Username="User2", Roll=2, RankPrio=3},
{Username="User4", Roll=10, RankPrio=2},
{Username="User5", Roll=9, RankPrio=2},
{Username="User3", Roll=32, RankPrio=2}
}
I want the list to be sorted like
_rolls = {
{Username="User2", Roll=2, RankPrio=3},
{Username="User3", Roll=32, RankPrio=2},
{Username="User4", Roll=10, RankPrio=2},
{Username="User5", Roll=9, RankPrio=2},
{Username="User1", Roll=50, RankPrio=1}
}
i know i can use this to sort by Rolls but i cant see a way to do both.
table.sort(_rolls, function(a,b) return a.Roll < b.Roll end)

Answer 1

You just need to write the comparison function so that it compares the Roll fields when the RankPrio fields compare equal:
_rolls = {
{Username="User1", Roll=50, RankPrio=1},
{Username="User2", Roll=2, RankPrio=3},
{Username="User4", Roll=10, RankPrio=2},
{Username="User5", Roll=9, RankPrio=2},
{Username="User3", Roll=32, RankPrio=2}
}
table.sort(_rolls,
function (a, b)
if a.RankPrio == b.RankPrio then
return b.Roll < a.Roll
else return b.RankPrio < a.RankPrio
end
end)
> table.inspect(_rolls)
1 =
RankPrio = 3
Username = User2
Roll = 2
2 =
RankPrio = 2
Username = User3
Roll = 32
3 =
RankPrio = 2
Username = User4
Roll = 10
4 =
RankPrio = 2
Username = User5
Roll = 9
5 =
RankPrio = 1
Username = User1
Roll = 50