table.sort throws " invalid order function"

user_10845029 0
Viewed 1063

I'm developing a simple friend system and want to sort the friendData with some rules.

I compared two friends' status , level and offline-Time.

PS:A friend has 3 status.(Online = 3,Busy = 2,Offline = 1).

Here's my code.

local function compare(friend1,friend2)
    local iScore1 = 0
    local iScore2 = 0
    if friend1["eStatus"] > friend2["eStatus"] then
        iScore1 = iScore1 + 1
    end
    if friend1["iLevel"] > friend2["iLevel"] then
        iScore1 = iScore1 + 1
    end
    if friend1["iOfflineTime"] < friend2["iOfflineTime"] then
        iScore1 = iScore1 + 1
    end
    return iScore1 > iScore2
end
table.sort(FriendData,compare)

It works when I add several friends.But when I get more friends,It throws exception "invalid order function for sorting". Can someone please tell me how to fix it? :)

lua sorting
1 Answers

Thanks to @Paul Hebert and @Egor Skriptunoff ,I Figure it out.

The key is that compare(a,b) and compare(b,a) should have different returned results.

That means:

  1. When iScore1 == iScore2,there should be an unique value for comparing(e.g.,accountID).

  2. Different compared value should have different scores.

Here is the new code.

local function compare(friend1,friend2)
    local iScore1 = 0
    local iScore2 = 0
    if friend1["eStatus"] > friend2["eStatus"] then
        iScore1 = iScore1 + 100
    elseif friend1["eStatus"] < friend2["eStatus"] then
        iScore2 = iScore2 + 100
    end
    if friend1["iLevel"] > friend2["iLevel"] then
        iScore1 = iScore1 + 10
    elseif friend1["iLevel"] < friend2["iLevel"] then
        iScore2 = iScore2 + 10
    end
    if friend1["iOfflineTime"] < friend2["iOfflineTime"] then
        iScore1 = iScore1 + 1
    elseif friend1["iOfflineTime"] > friend2["iOfflineTime"] then
        iScore2 = iScore2 + 1
    end
    if iScore1 == iScore2 then --They are both 0.
        return  friend1["accountID"] > friend2["accountID"]
    end
    return iScore1 > iScore2
end
table.sort(FriendData,compare)
user_108450290
Related