diffictul situation of ordering objects in a group

[coolromin]

@davebollinger

as per all previous advice…

assume you have your objects in an array (ie, table with numeric keys) (we don’t care HOW they got there, just that they’re there, for discussion’s sake)
local objList = { obj1, obj2, obj3, obj4, obj5, obj6 }

now sort that list on y ascending (“back” to “front”, painter’s algorithm):

local function sortfn(a, b ) return a.y < b.y end
table.sort(objList, sortfn)

now iterate the table by numeric keys

for i=1,#objList do – or k,v in ipairs
objList[i]:toFront()
end

hth

I found out that…it works when tried with indexed tables, but since my table use keys instead of indexes, it doesn’t work.

Here is a sample code if u wanna try…

local objList = { } local obj1 = display.newCircle(0,0,0) objList["obj1"] = obj1 local obj2 = display.newCircle(0,0,0) objList["obj2"] = obj2 local obj3 = display.newCircle(0,0,0) objList["obj3"] = obj3 local obj4 = display.newCircle(0,0,0) objList["obj4"] = obj4 local obj5 = display.newCircle(0,0,0) objList["obj5"] = obj5 local obj6 = display.newCircle(0,0,0) objList["obj6"] = obj6 obj1.y =10 obj2.y =40 obj3.y =20 obj4.y =50 obj5.y =60 obj6.y =30 local function sortfn(a, b ) return a.y \< b.y end --no matter if u coment this line or not, function will always produce the same result... table.sort(objList, sortfn) for k,v in pairs(objList) do --objList[i]:toFront() print(objList[k].y) end

RESULTS…

40 30 50 60 10 20

[davebollinger]

re-read my original post, you missed something important…

>> for k,v in pairs(objList) do

nope – pairs() defeats the whole purpose of sorting a list!, as the order of iteration with pairs() is undefined. you MUST iterate numerically, either with “for i=1,#table” or “for k,v in ipairs(table)” (note the “i” in ipairs, critical difference)

once sorted back-to-front, and iterated in numeric order, toFront() will indeed work.

[EDIT] it occurs to me that THIS is the part you might not “get”:

-- assuming your current list is by alpha keys: local anUnsortableList = ..whatever, your current list as is -- so MAKE a sortable list: local aSortableList = {} for k,v in pairs(anUnsortableList) do aSortableList[#aSortableList+1] = v end -- then sort it local function sortfn(a, b ) return a.y \< b.y end table.sort(aSortableList,sortfn) -- then order your objects in the display for i=1,#aSortableList do aSortableList[i]:toFront() end -- done, no longer need this aSortableList = nil

[coolromin]

@davebollinger this is exactly what i wanted…i don’t have words to thank you, i was looking for this for a long time

I am using it in an enterFrame function so i hope it is ok to do this every frame?

Thanks again!!!