Tech News Back Issues Issue: 103002

Introduction to the Omnis Web Client: Part 3, Getting started with a web client application.

By Dr Caroline Wilkins
iB2B Systems Ltd

www.ib2bsystems.com
caroline@ib2bsystems.com

In the previous newsletter, we looked at some of the web client components available to the developer. In the next few issues of the newsletter, we are going to put some of them together to build a basic application that will enable a user to enter data, upload a picture to the Omnis server to go with the record and then view the data and associated picture. The application we will build is similar to one that is used by animal rescue shelters in the RescuePet system (www.rescuepet.org.uk) to upload details and photos of animals for re-display on a public web site. This example library can easily be adapted for any number of applications.

In this newletter, we create a library, a database, connect library to database using Startup_Task, create a schema and drag it into the database to create a corresponding table. All this is basic Studio programming and does not involve web client specific work. That will follow in the next newsletter.

1. Create a library

1.1 Create a new library for your project in C:\RescuePet\ directory. To do this, select the 'Library' >> 'New' menu option from the Library browser menubar.
1.2 Choose a name for your library.

2. Create a database

2.1 Open the Data file Browser from the View menu and select 'New' from the Datafile menu. Choose a name for your database. For this example, use RescuePet.df1. Put it in the same directory as your library: C:\RescuePet.
2.2 Close the database. We will be making a connection to it in the Startup_Task.
2.3 Close Data File Browser window.

3. The Startup_Task

3.1 In the Libraries browser, double click on the RESCUEPET library to view the contents of the library. There should just be a Startup_Task. The code inside this class executes when the library is opened. We will use it to create a session to the database.
3.2 Double click on the Startup_Task to open the method editor

4. Connecting to the database

4.1 Enter the code given below. This will open a session to the database (RescuePet.df1) that you just created. Note that you must give the full path to the database file in line

Start_Up.$construct
Set current session {RescuePet}
Start session {dOMNIS}
If flag false
  OK message Configuration error {Unable to load the OMNISSQL DAM}
  Quit method
End If
Set hostname {C:\RescuePet\RescuePet.df1}
Logon to host (Omnis Character Set)
If flag false
  OK message Error opening session {[sys(131)]: [sys(132)]}
  Quit method
End If


4.2 There are traps with error messages to tell you if there is a problem with the Data Access Module (DAM) or with opening the session.

4.3 Close the method editor window when you are done.
4.4 To test this code, open up the SQL Browser from the Tools menu. There will be no sessions open yet, but you can force the StartUp_Task to open the RESCUEPET database session by right clicking on StartUp_task and selecting 'Close Task', then right clicking again and selecting 'Open Task'. You should see the RESCUEPET session appear.

5. Creating a Schema

5.1 Now it's time to start creating the structure of the database. We use a Schema class to hold the columns of the database table. This is Omnis's view of the database, but can also be used to create database tables, as you will see.
5.2 Click on the 'New Schema' (7th from left) icon in the component store and drag into your RescuePet library browser window. Name the schema 'Dog'.

6. Designing the Schema

6.1 Double click on the Dog Schema class and enter some fields to hold data about dogs. For this exercise, try:

  Id (Number, Long Integer)
  Name (Character, 100)
  Age (Number, Long Integer)
  Gender (Character, 10)
  Size (Character, 10)
  ShelterId (Number, Long Integer)


6.2 For Server table or view, at the top of the schema editor, enter 'Dog'.
6.3 Set Primary Key and No nulls to kTrue for the 'Id' column.
6.4 Close the Dog Schema.

7. Creating a table from a schema

7.1 Double click on the RESCUEPET session to open the RESCUEPET session window.
7.2 Double click on 'Tables' within that window to open the RESCUEPET_Tables window. There are no tables in there yet because we have not created any.

7.3 To create a Dog table, click on the Dog schema in the Library browser and drag into the RESCUEPET_Tables window.
7.4 Double click on the Dog table to view the table columns and verify that you have created the table correctly.

We have now created an Omnis library, an Omnis database, we have programmed a startup task that will open a session to that database and have created a Dog schema in the library to represent a Dog table in the database. We are now ready to build a user interface. In the next newsletter, we will use the library and database we have built here and go on to create a web client interface to the database.

 
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