Sweet Snippet 系列之 Lua表排序

function order_pairs(tbl)
    local names_buffer = {}
    for name, _ in pairs(tbl) do
        table.insert(names_buffer, name)
    end
    table.sort(names_buffer, function(a, b) return tostring(a) < tostring(b) end)
    
    local table_index = 0
    local function iterator()
        table_index = table_index + 1
        local key = names_buffer[table_index]
        return key, tbl[key]
    end
    
    return iterator
end

local function print_table(tbl)
    for k, v in pairs(tbl) do
        print(k .. " = " .. v)
    end
    print "========"
end

local function print_table_order(tbl)
    for k, v in order_pairs(tbl) do
        print(k .. " = " .. v)
    end
    print "========"
end

local t = { [4] = "test", "order", b = "pairs", [2] = "another", a = "string" }

print_table(t)

print_table_order(t)

-- order pairs implementation :
-- order is number first, then sort by tostring

local function default_sort_comp(k1, k2)
    if type(k1) == "number" and type(k2) == "number" then
        return k1 < k2
    elseif type(k1) == "number" then
        return true
    elseif type(k2) == "number" then
        return false
    else
        return tostring(k1) < tostring(k2)
    end
end

function order_pairs(t, sort_comp)
    -- get original keys and do sort
    local keys_buffer = {}
    for k, v in pairs(t) do
        table.insert(keys_buffer, k)
    end
    table.sort(keys_buffer, sort_comp or default_sort_comp)
    
    -- gen iterator
    local current_index = 0
    local function iterator()
        current_index = current_index + 1
        local cur_key = keys_buffer[current_index]
        return cur_key, t[cur_key]
    end
    
    return iterator
end