KRL Safari: KRUD Redux - Kynetx CRUD with Persistent Variables

2011-10-10T16:29:00.001-06:00

Recent updates to the Kynetx platform related to Hash expressions has given me the opportunity to revisit my previous post. If your WebApp has modest requirements for storage of data it is worthwhile considering the use of Persistent Variables. To demonstrate the salient principles of using persistent variables as a datastore, a simple Kynetx WebApp addressbook is provided.

View Demo Online Download Source Code

The addressbook application stores the name, email and phone number of each person. The addressbook data is stored in a single persistant variable as key/value pairs. With the persons name used as the key:

"SomeName" : {
    "Name"  : "SomeName",
    "Email" : "SomeEmail",
    "Phone" : "SomePhone"
}

Since there is a lot of to wade through, so let me point out that parts specifically related to reading, writing and remove entries in the addressbook. In order to read all of the entries in the addressbook the following ruleset is used:

foreach ent:KRUDaddresss.keys() setting (addressKey)
pre {
  email = ent:KRUDaddresss{[addressKey, "Email"]};
  phone = ent:KRUDaddresss{[addressKey, "Phone"]};
  addressRow = &lt;&lt;
      
          #{addressKey}
          #{email}
          #{phone}
          Remove
      
  >>;
}
{
  append('#panelAddressList .DataTable tbody', addressRow);
}

New entries for the addressbook are entered via a standard HTML form. With a watch() placed on the submit the following rule captures the entry from the form, builds a new entry and adds it to the persistent variable:

select when submit "#formAddressAdd"
pre {
  formName  = event:param("formName");
  formEmail = event:param("formEmail");
  formPhone = event:param("formPhone");
  formHash = {
      "Name"  : formName,
      "Email" : formEmail,
      "Phone" : formPhone
  };

  KRUDaddresss = ent:KRUDaddresss || {};
}
{ noop(); }
fired {
  set ent:KRUDaddresss{[formName]} formHash;
}

Entries are removed from the addressbook by calling the following rule with an entries name as the event parameter:

pre {
  keyName = event:param("keyName");
}
{ noop(); }
fired {
  clear ent:KRUDaddresss{keyName};
}

You can play with the online demo to see the end results. And you can get the source code for the whole WebApp on GitHub. Heads up, there's a lot of code in the WebApp related to the GUI, that's why I wanted to call out the salient CRUD elements above. Enjoy!

11 Oct 2011: Revised code for adding new addressbook entries to use the new expression syntax for Persistent Hashes. When these new expressions are used you avoid loading, binding and transferring the entire hash.

View Demo Online Download Source Code

KRL Safari: KRUD - Kynetx CRUD with Persistant Variables

2011-02-04T10:25:00.000-07:00

Got KRUD? In this KRL safari we will be using persistance variables as a database. While most web developers have written code to access a database, most Kynetx applications retrieve their data via RESTful web services. But there are times when a persistant data store is needed. Building a one off web service to host the data is certainly an option, but if the storage needs are moderate you can simply use a persistant variable. After all 2 million bytes of data can be stored in a persistant variable!

To keep the focus on the mechanics a simple data structure is used to demonstrate KRL CRUD ... an array of strings which will be used to implement a tag cloud. The demo provides a web interface to see all of the strings in the tag cloud, add new tags and delete tags. To permit the demo to be accessible to a broad audience, it has been distributed using a site tag. Just visit the demo page to see all of the current tags which have been entered by all who have used the application. You can add a new tag by entering text into the form, then click the Add button. To delete a existing tag simply click on the text of the tag.

While the KRL code has comments thoughout, it should be emphasized that application persistent variables accessed in the rule prelude:

TagCloud = app:TagCloud;

And the updated persistent variable are saved in the postlude:

set app:TagCloud TagCloud;

Adding a new value to the persistent variable is performed using the union operator:

newCloud = TagCloud.union(cleanTag);

Removing a value from the persistent variable is done using the difference operator:

newCloud = TagCloud.difference(tagText);

To see the implementation using a complex data structure take a look at Kynetx App A Day 28 Updating User's List When User Joins App.

Hey! Where's the U in KRUD? Multiple choice response:

Left as an exercise for the reader
Updated was not needed for demo
I'm lazy :)

Enjoy!

edoism

KRL Safari: KRUD Redux - Kynetx CRUD with Persistent Variables

KRL Safari: KRUD - Kynetx CRUD with Persistant Variables