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This is good example of how we can Eliminate bottlenecks with IguanaX usePrefix Namespaces for Separating Concerns by building a custom file reader component which has a simple interface for a unique purpose rather than using a general purpose no code solution - see The problem with no-code solutions.

Here’s a scenario:

A large lab needs to have a file reading component which can feed files from different customers based on the prefix of the file, i.e. some files start with JJ99, others XYZ etc. depending on the source.

Let’s do it!

Create component from Git URL

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title	Import Use +FROM URL to import a custom version of the file reader from git@bitbucket.org:interfaceware/file_tutorial.git

component for this tutorial

This component generates some test files to make it easier to learn how to make a custom file reader.

You can useCreate component +FROM URL to import the component.

Copy paste the URL from here:

Code Block
git@bitbucket.org:interfaceware/file_tutorial.git

This component generates some test files to make it easier to learn how to make a custom file reader

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title	Click Edit on the component card, then MAKE A COPY AND EDIT to open the Translator editor

Refer to Edit a Component to see how it's done if you have not done this before.

See Customizing components to see how done if you have not done this before

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title	Open Examine the Custom Field configurations in the component in the translator with the Customize link

config.json

To simplify the tutorial we have set these up a ClientList with the filename prefix Ids. Click on the config.json and you should see:

Image Added

See Custom Fields to understand how this was created.

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title	Click on MatchRules.lua in the Project Tree to see where we need to alter the code

Navigate to MatchRules.lua in the project tree Project Tree. This is the function we need to alter:

Code Block

language	lua

function MatchFile(FileName)
   return true
end

The file reader component is deliberately simple and uses /wiki/spaces/IXB/pages/3181903910 separation of concerns to make it more obvious how to modify the code to meet new needs. We need this function to return true when the matching criteria are met.

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title	Let's extract the filename using FILfilename() from the FIL Library, so we can look at it:

Change the matching to add in two lines so we can see the filenames we need to filter on.

Code Block

language	lua

function MatchFile(FileName)
   local JustFileName = FILfilename(FileName)
   trace(JustFileName)
   return true
end

These are the concepts we have used:

A function
FIL Library used to get the file name
Using trace() function

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title	Examine the custom configuration in the component

To simplify the tutorial we have set these up already. Click on the config.json and you should see:

Image Removed

See Custom Fields to understand how this was created.

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title	Extract Edit MatchRules.lua to extract the prefixes from the custom fields

Now we need Create a second function, APPidList, to extract the fields ClientList prefixes from the custom configuration. So we start with this functionfields and update MatchFile to call APPidList.

You can replace the contents of the MatchRules.lua file with this new code:

Code Block

language	lua

function APPidList()
   local IdList = component.fields()["ClientList"]
   return IdList
end

function MatchFile(FileName)
   local IdList = APPidList()
   trace(IdList)
   local JustFileName = FILfilename(FileName)
   trace(JustFileName)
   return true
end

Concepts used:

/wiki/spaces/IXB/pages/3181903910

Writing a function
Using trace() function
Using APP as a prefix, see Using prefixes for naming code to maintain a common naming convention
Custom Fields

So we add one line

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title	Break the comma delimited string into a list

to get each prefix Id

We can quickly do this by adding one line to AppidList after line 2:

Code Block

language	lua

IdList = IdList:split(",")

You should see something like:

Concepts used:

String:split()

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title	Make a matching function which takes the prefix and sees if the filename starts with it

So now we make Create a third function, APPmatchPrefix, to determine if the file name matches filename matches the prefix. You can copy the code below:

Code Block

language	lua

function APPmatchPrefix(Prefix, FileName)
   local Part = FileName:sub(1, #Prefix)
   trace(Part, Prefix)
   return (Part == Prefix)
end

And we’ll call it as part of the MatchFile routine:See the screenshot below and add a line to MatchFile to call and invoke AppmatchPrefix.

Concepts used:

A function
https://interfaceware.atlassian.net/wiki/spaces/IXB/pages/2684813341/Operator+on+# Operator on Strings to get the length of the prefixhttps://interfaceware.atlassian.net/wiki/spaces/IXB/pages/2685337684/String+sub+-+get+a+substring
String:sub()
Equality and inequality operators

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title	Now change the matching code in MatchFile() so we go iterate through all the of the prefix list

Let’s modify the code to go through the entire list of prefixes:

Code Block

language	lua

for i = 1, #IdList do
   if APPmatchPrefix(IdList[i], JustFileName) then 
      return true
   end
end
return false -- we didn't match anything

And this is what you should see:

Image Removed

Image Added

Concepts used:

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title	Commit your changes, alter the component to run on the new commit, and run it!

Commit and Push Changes to Git and go to the component card for Choosing the code to run for your component.

And You’re done! The next steps are how you could further refine the code

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title	Make the configuration more robust by striping trimming the white space from the list ClientListof prefixes

This means refining the APPidList function.

That would involve looping through the list and removing white space from each ID:

Concepts:

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title	Customize the logging

See Custom Logging

using iguana.log*

Add intuitive Custom Logging for your component to increase visibility into processing and adding meaningful messages to help with troubleshooting.

You can see an example of this in main.lua on line 25:

Code Block

language	lua

iguana.log("Polling every "..Polltime.." seconds");

Try it for yourself!

See Concatenating strings for a quick explanation on the double-dot notation.

See Custom Status

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title	Customize the status

using component.setStatus{data="Text"}

Add Custom Status for your component to have it display real time updates at the bottom of the component card as its running.

This component already creates custom status on lines 31-36 of main.lua.

Try it for yourself!

There is no limit to how you can streamline the usage of a custom component - if that helps address a bottleneck, then it is well worth it.

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