COUNT Library

Often times in interfaces we have this use case where we have a datasource that will give us information with a sequence of incrementing IDs. For instance the IMAP email protocol is an example of this.

If you only had 20 emails and each email takes a second to query then a for loop would work fine. But what if you 100,000 emails? You really need to be able to wake up a component, get a small batch of say 10, iterate and store the next ID and then get the next 10 and so on.

It’s nice to control where you start from and keep incrementing the value as we go forward. The COUNT library solves this problem.

Import the COUNT library into your project.

See Import Library if you need a refresher on how to do it.

Create a custom number field called 'NextId' and set it to the value 1 in your card.

See Custom Fields

local NextId = COUNTget("NextId") is how we fetch the data

This is how we get the data from a custom field called NextId.

local NextId = COUNTget("NextId")

COUNTset("NextId", NextId) is how we set it.

So this saves the new value of the custom field in the custom field value file.

COUNTset("NextId", NextId)

It means we can see the NextId in the card view of the component - and we can set it too!

This is a complete little program to increment a custom number field

require "COUNT.COUNT"

function main(Data)
   --Poll the component every 2 seconds
   component.setTimer{delay=2000}
   local NextId = COUNTget("NextId")
   NextId = NextId+1
   COUNTset('NextId', NextId)
end

The COUNT library solves this problem by giving a convenient interface to GET/SET a custom field value

Remember Custom Fields the values for these are stored on disc in JSON. This means we can load and save them programmatically.

This is how this library works.

This is a very useful pattern for lots of Feeder interfaces.