How to sort this lua table?

Question

I have next structure

self.modules = {
    ["Announcements"] = {
        priority = 0,
        -- Tons of other attributes
    },
    ["Healthbar"] = {
        priority = 40,
        -- Tons of other attributes
    },
    ["Powerbar"] = {
        priority = 35,
        -- Tons of other attributes
    },
}

I need to sort this table by priorty DESC, other values does not matter. E.g. Healthbar first, then Powerbar, and then going all others.

// edit.

Keys must be preserved.

// edit #2

Found a solution, thanks you all.

local function pairsByPriority(t)
    local registry = {}

    for k, v in pairs(t) do
        tinsert(registry, {k, v.priority})
    end

    tsort(registry, function(a, b) return a[2] > b[2] end)

    local i = 0

    local iter = function()
        i = i + 1

        if (registry[i] ~= nil) then
            return registry[i][1], t[registry[i][1]]
        end

        return nil
    end

    return iter
end

What do you mean by sort? Tables with string keys are unsorted. To sort it you'd need to change the data structure. What is your expected result? — ahilsend
– ahilsend, Commented Jul 29, 2013 at 17:34

Tiago Costa · Accepted Answer · 2013-07-29 17:54:45Z

5

You can't sort a records table because entries are ordered internally by Lua and you can't change the order.

An alternative is to create an array where each entry is a table containing two fields (name and priority) and sort that table instead something like this:

self.modulesArray = {}

for k,v in pairs(self.modules) do
    v.name = k --Store the key in an entry called "name"
    table.insert(self.modulesArray, v)
end

table.sort(self.modulesArray, function(a,b) return a.priority > b.priority end)

for k,v in ipairs(self.modulesArray) do
    print (k,v.name)
end

Output:

1       Healthbar       40
2       Powerbar        35
3       Announcements   0

edited Jul 29, 2013 at 17:54

answered Jul 29, 2013 at 17:34

Tiago Costa

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