Resource containers

A resource container is a part's storage for a resource: a fuel tank's methalox, a pod's monopropellant, a battery's charge. Each container names a resource, a capacity, and how much it starts with. The parts module exposes a part's containers as a typed list with a one-call helper for adding them.

The containers list

A part's containers are on part.resourceContainers. The list is keyed by resource name and has two helpers:

• part.resourceContainers:Add(type, capacity, initial, nonStageable) adds a container.

• part.resourceContainers:Has(type) tests whether the part already stores that resource.

Adding storage

The common case is giving a part a resource it did not store, or topping up its capacity:

PM.Parts:Patch("AddMonopropToPod")
        :Named("pod_1v_command")
        :Do(function(part)
            part.resourceContainers:Add("MonoPropellant", 100, 100)
        end)

The arguments are:

• **type** is the resource name ("MonoPropellant", "Methalox", "ElectricCharge", and so on).

• **capacity** is how many units the container holds.

• **initial** is how many units it starts filled with. It is optional and defaults to 0. Pass the same value as the capacity for a full tank, as above.

• **nonStageable** is optional and defaults to false. Set it true for storage that should be exempt from staging (for example a reserve that is never drained as a stage).

Guarding against duplicates

Use :Has to avoid adding a container the part already has, which keeps a broad patch from doubling up storage on parts that already store the resource:

:Do(function(part)
    if not part.resourceContainers:Has("ElectricCharge") then
        part.resourceContainers:Add("ElectricCharge", 50, 50)
    end
end)

You could also express "only parts without this resource" as a gate with :Requires, depending on whether you want the whole patch to skip or just the one container.

Containers versus the resource module

Adding a container puts the resource storage on the part. Defining the resource itself (its mass per unit, its flow mode, its cost) is a separate job handled by Resources. A container references a resource by name. The resource has to exist for that reference to mean anything, whether it is a stock resource or one you defined.