Component Registry

The Component Registry allows accessing all currently available Components and is the most convenient way of accessing components. Every Lua vm instance contains a global variable called components which contains this object.

ComponentRegistryUD methods

Name	Type	Description
:list()	function() -> (string, userdata), table, nil	Returns an iterator function that, in each invocation returns a string representing the type of the current component along with the actual userdata instance.
:getFirst(componentType:string)	userdata	Returns the first component of the given componentType or nil if no matching component exists.

While :list() looks very intimidating, it can simply be used in a for-loop in place of ipairs(*). The built-in UEFI uses the following code to iterate over all components to find any bootable devices:

local bootables = {}
for compType, elem in components:list() do
    print("- " .. compType)
    if compType == "massStorage" then
        if elem:fileExists("boot.lua") then
            -- we found a bootable medium, use it as default if not already set
            defaultBoot = defaultBoot == nil and idx or defaultBoot
            bootables[idx] = elem
        end
        idx = idx + 1
    end
end

Notes

Technically the component registry is not a component, but it still is listed in this category as it is closely tied to this topic.