pairs

• Used to traverse the dictionary

Function Prototype

API

pairs(t: <table>, f: <function>, ...)

Parameter Description

Parameter	Description
t	Table to traverse
f	Function to process values (optional)
...	Variable arguments for function (optional)

Usage

This is lua's native built-in api. In xmake, it has been extended in its original behavior to simplify some of the daily lua traversal code.

First look at the default native notation:

local t = {a = "a", b = "b", c = "c", d = "d", e = "e", f = "f"}

for key, val in pairs(t) do
    print("%s: %s", key, val)
end

This is sufficient for normal traversal operations, but if we get the uppercase for each of the elements it traverses, we can write:

for key, val in pairs(t, function (v) return v:upper() end) do
     print("%s: %s", key, val)
end

Even pass in some parameters to the second function, for example:

for key, val in pairs(t, function (v, a, b) return v:upper() .. a .. b end, "a", "b") do
     print("%s: %s", key, val)
end

NOTE

Since v3.0.9, xmake's built-in Lua runtime has been upgraded to 5.5. To preserve the familiar semantics where the loop body can safely reassign the loop key, xmake's sandbox pairs keeps the iteration state in an internal closure, so the following idiom keeps working without changes:

for k, v in pairs(t) do
    k = k:gsub("_", "-")
    do_something(k, v)
end