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Often times in interfaces we have this use case .

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where we have a datasource

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For instance in email protocols like the IMAP protocol will give each email a unique sequential ID.

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titleWe need to have a convenient way to set the ID we want to begin from but we need to keep on incrementing it

So for my email I would like to begin at say message 10000 and then progressively keep moving forward from there.

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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 have 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.

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titleCreate a custom component using +COMPONENT

To test out the COUNT library, make a custom component. See Create a Component.

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titleThe 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 what this library does.

Import the COUNT library into your project

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

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titleCreate a custom number field called 'NextId' and set it to the value 156 in your card

NextId
First, in config.json add your Custom Fields. Then go to your component card and set the value to 156.

Note: You’ll need to change your component to use the DEVELOPMENT commit to see the newly added custom field. See Choosing the code to run for your component.

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

This is how we We can use COUNTget to get the data from a the custom field called NextMailId.NextId.

We increment NextId by 1 each time the component runs.

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local NextId = COUNTget("NextId") 
NextId = NextId+1
So this It NextMailId
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titleCOUNTset("NextMailIdNextId", NextId) is how we set it.
the count value
title

COUNTset saves the new value of the custom field in the custom field value file.

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COUNTset("NextId", NextId)

This means we can see the

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

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titleTo test this, we can set the component to run every 2 seconds using component.setTimer{delay=}

You can use component.setTimer{} is used here to run main every 2 seconds.

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

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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
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titleRun the component from the component card view and see the NextId value change.
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titleThe COUNT library solves this problem by giving a convenient interface to get and set a custom field value

Remember, the Custom Fields values 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 Feeder interfaces. It’s used as part of the IMAP Email Feed component.