|
"Men show their
characters in nothing more clearly than in what they think
laughable." Johann Wolfgang von Goethe (1749 - 1832) |
Read
first then play the video:
FRM-VIDEO -(Hands-On
12) How to use Global Variable and Trigger (WHEN-NEW-FORM-INSTANCE)
Global Variable, Trigger
Global Variable
A Global Variable is a
binding variable that can be used by multiple Form Modules.
Form Trigger
A forms trigger is a
block of PL/SQL code that adds functionality to your application.
Triggers are attached to objects in your application. When a trigger
is fired, it executes the code it contains. Each trigger"s name
defines what event will fire it; for instance, a WHEN-BUTTON-PRESSED
trigger executes its code each time you click on the button to which
the trigger is attached. Or, we can say, a forms trigger is a
set of PL/SQL actions that happen each time an event such as
when-checkbox-changed, when-button-pressed, or
when-new-record-instance occurs. You can attach several triggers
to a data query. The most popular of them are the PRE-QUERY and
POST-QUERY.
POST-QUERY trigger
The PRE-QUERY
trigger fires before the select statement is finalized. The POST-QUERY
trigger fires before selected records are presented to the user. It
fires after records are retrieved but before they are displayed. So,
you can use it to enhance a query"s records in a number of ways.
Your Post-Query trigger can contain code to calculate or populate
control items.
WHEN-NEW-FORM-INSTANCE
trigger
Some other useful triggers
are: PRE-INSERT and WHEN-NEW-FORM-INSTANCE.
A PRE-INSERT
trigger fires once before each new record is inserted in a commit
process. The "WHEN-NEW-FORM-INSTANCE" trigger will be used
to prepare objects or an action when entering to a new form. It fires
when the form is entered.
Hands-ON
Now, your client desires it
would be better if they could get specific history of product price
rather than entire product history prices table. They want you to add
more functionality to their application to display only current
history of product prices information.
Note: The current product
would be defined by where the position of your cursor is.
You have been assigned to
modify their application to query only history of product price
information for a product rather than entire table.
See Figure 14.
Your tasks are:
1- Automate the "product
history prices" application to query only a history of product
prices.
2- Pass product ID as a
parameter between these two Form applications.
3- Run and test all user
functional requirements.
F You will learn how
to: use and assign global variable, pass global variable from one Form
to another, use global variable to execute query base on its
parameter, create and use the "WHEN-NEW-FORM-INSTANCE"
trigger, use tab canvas, use "object navigator," use "Data
Blocks," use "Layout Editor," use "Property Palette," use
"Run Form," and "Execute Query."
Figure 14
Open a Module
In the "Object Navigator"
window, highlight Forms. Go to the Main menu and choose "File,"
select "Open" to open an existing form (customer_orders_V11)
in the "iself" folder.
Save Modules
Click on the "CUSTOMER_ORDERS_V11"
form. The color changes to blue. Then change its name and save the
Form name as version 12 (customer_orders_12). This way the
original form is untouched.
Also, you should save the
"Product History Prices Data Entry" (PROD_DE) Form name as version
2 (PROD_DE_V02).
Now, we want to change the
application to query all the product history prices for an item that
the cursor is on.
Temporary Holder
In the PROD_DE_V02 form,
expand the form, highlight the Data Blocks item and then click on the
green "+" sign to create a data block.
New Data Block
In the "New Data Block"
window, choose the "Build a new data block manually" option and
click "OK."
Change a property palette
sheet
Now, you have a new data
block (Blockn). Right click on it and open its Property Palette. In
its property palette, change its name to CONTROL_BLOCK. Change
"Database Data Block" to "NO." Close the window.
Create an Item
In CONTROL_BLOCK, create a
new item. Open its property palette. Change the "name" item
to "TEMP_VALUE." Change its datatype to NUMBER with length 7
bytes. Change "database item" to "NO." Close the window.
Copy Value from Item
Select "Prodid" on the
price data block; and open its property palette. For "Copy Value
from Item" type "control_block.temp_value." Close the
window.
Create a trigger
In the PROD_DE_V02 form,
create a "WHEN-NEW-FORM-INSTANCE" trigger at Form level.
WHEN-NEW-FORM-INSTANCE
trigger
In the Trigger window, type
"W" and "N" and select the WHEN-NEW-FORM-INSTANCE
trigger.
PL/SQL Editor
In the PL/SQL Editor, write
a PL/SQL procedure to move the global prodid item value into the
temp_value item. Then go to the "price" data block and execute the
query function.
(PL/SQL Editor)
:temp_value := :global.prodid;
GO_BLOCK ("price");
EXECUTE_QUERY;
Compile a trigger
Compile the trigger and
close the window.
Compile a module
Highlight the Form and save
it. Then go to File > Administration > Compile file to compile
it.
Create a Push Button
On the CUSTOMER_ORDERS_V12
Form, right click on the "Product History Data Entry" push button
in the ITEM tap canvas to select "Smart Trigger" and select the
"WHEN-BUTTON-PRESSED" trigger.
WHEN-BUTTON-PRESSED trigger
In the PL/SQL Editor, write
a PL/SQL procedure to move the PRODID value into the global prodid
item and call the Product History Price Data Entry form.
(PL/SQL Editor)
:GLOBAL.prodid := NAME_IN("item.prodid");
OPEN_FORM("c:_de_v02");
Compile the trigger and
then close the window.
Run the Form
Run the application.
Execute Query
Click on the "Execute
Query" icon.
Navigate the application
Navigate through the
application.
Highlight a product id and
then click on the "Product History Prices Data Entry" push button.
Now, you should only see
information about that specific product id not all the products.
Repeat the process for some
other items.
Then, close all the windows
and save the changes.
|
"We all carry
around so much pain in our hearts. Love and pain and beauty.
They all seem to go together like one little tidy confusing
package. It's a messy business, life. It's hard to figure--full
of surprises. Some good. Some bad." Henry Bromel, Northern
Exposure, The Big Kiss, 1991 |
Questions:
Q: How do you define a
binding variable in a multiple forms?
Q: How do you assign a
value to a global variable?
Q: How do you pass a global
variable value from one form to another?
Q: How do you use a global
variable to execute a query based on its parameter?
Q: Describe the
"WHEN-NEW-FORM-INSTANCE" trigger.
Q: How do you create the
"WHEN-NEW-FORM-INSTANCE" trigger?
Q: Now, your client desires
it would be better if they could get specific history of product price
rather than entire product history prices table. They want you to add
more functionality to their application to display only current
history of product prices information.
Note: The current product
would be defined by where the position of your cursor is.
You have been assigned to
modify their application to query only history of product price
information for a product rather than entire table.
See Figure 14.
Your tasks are:
1- Automate the "product
history prices" application to query only a history of product
prices.
2- Pass product ID as a
parameter between these two Form applications.
3- Run and test all user
functional requirements.
|