Working with objects

In PowerScript targets, you can:

• Create
  new objects
• Create new objects using inheritance
• Open existing objects
• Run or preview objects

After you create or open an object, the object displays in
its painter and you work on it there.

Creating new objects

To create new
objects, you use the New dialog box.

To create a new object:

1. Do one of the following:

   • Click
     the New button in the PowerBar.
   • Select File>New from the menu bar.
   • On the Workspace tab of the System Tree, right-click
     on a workspace or target name and select New from the pop-up menu.

2. In the New dialog box, select the appropriate
   tab page for the object you want to create.

   You use icons on the PB Object tab page for creating new user
   objects, windows, menus, structures, and functions.

3. Select an icon and click OK.

Creating new objects using inheritance

One
of the most powerful features of PowerBuilder is inheritance. With inheritance,
you can create a new window, user object, or menu (a descendent object)
from an existing object (the ancestor object).

To create a new object by inheriting it from an
existing object:

1. Click the Inherit button in the PowerBar,
   or select File>Inherit from the menu bar.

2. In the Inherit From Object dialog box, select
   the object type (menu, user object, or window) from the Object Type
   drop-down list. Then select the target as well as the library or
   libraries you want to look in. Finally, select the object from which
   you want to inherit the new object.

   

   Displaying objects from many libraries To find an object more easily, you can select more than one
   library in the Libraries list. Use Ctrl+Click to select
   additional libraries and Shift+Click to select a range.

3. Click OK.

   The new object, which is a descendant of the object you chose
   to inherit from, opens in the appropriate painter.

For more information about inheritance, see Chapter 13, “Understanding Inheritance .”

Naming conventions

As you use PowerBuilder to develop your application, you create
many different components that require names. These components include
objects such as windows and menus, controls that go into your windows,
and variables for your event and function scripts.

You should devise a set of naming conventions and follow them
throughout your project. When you are working in a team, this is
critical to enforcing consistency and enabling others to understand
your code. This section provides tables of common naming conventions.
PowerBuilder does not require you to use these conventions, but
they are followed in many PowerBuilder books and examples.

All indentifiers in PowerBuilder can be up to 40 characters
long. The first few characters are typically used to specify a prefix
that identifies the kind of object or variable, followed by an underscore
character, followed by a string of characters that uniquely describes
this particular object or variable.

Object naming conventions

Table 5-2 shows common prefixes
for objects that you create in PowerBuilder.

Table 5-2: Common prefixes for objects

Prefix	Description
w_	Window
m_	Menu
d_	DataWindow
pipe_	Data Pipeline
q_	Query
n_ or n_standardobject_	Standard class user object, where standardobject represents the type of object; for example, n_trans
n_ or n_cst	Custom class user object
u_ or u_standardobject_	Standard visual user object, where standardobject represents the type of object; for example, u_cb
u_	Custom visual user object
f_	Global function
of_	Object-level function
s_	Global structure
str_	Object-level structure
ue_	User event

Variable naming conventions

The prefix for variables typically
combines a letter that represents the scope of the variable and
a letter or letters that represent its datatype. Table 5-3 lists the prefixes
used to indicate a variable’s scope. Table 5-4 lists the prefixes
for standard datatypes, such as integer or string.

The variable might also be a PowerBuilder object or control. Table 5-5 lists prefixes
for some common PowerBuilder system objects. For controls, you can use
the standard prefix that PowerBuilder uses when you add a control
to a window or visual user object. To see these prefixes, open the
Window painter, select Design>Options, and look at the
Prefixes 1 and Prefixes 2 pages.

Table 5-3: Prefixes that indicate the scope
of variables

Prefix	Description
a	Argument to an event or function
g	Global variable
i	Instance variable
l	Local variable
s	Shared variable

Table 5-4: Prefixes for
standard datatypes

Prefix	Description
a	Any
blb	Blob
b	Boolean
ch	Character
d	Date
dtm	DateTime
dc	Decimal
dbl	Double
e	Enumerated
i	Integer
l	Long
r	Real
s	String
tm	Time
ui	UnsignedInteger
ul	UnsignedLong

Table 5-5: Prefixes for
selected PowerBuilder system objects

Prefix	Description
ds	DataStore
dw	DataWindow
dwc	DataWindowChild
dwo	DWobject
env	Environment
err	Error
gr	Graph
inet	Inet
ir	InternetResult
lvi	ListViewItem
mfd	MailFileDescription
mm	MailMessage
mr	MailRecipient
ms	MailSession
msg	Message
nvo	NonVisualObject
tr	Transaction
tvi	TreeViewItem

Opening existing objects

You can open existing objects through the Open dialog box
or directly from the System Tree.

To open existing objects:

1. Click the Open button in the PowerBar or
   select File>Open from the menu bar.

   When using the System Tree To open an existing object directly from the System Tree,
   either double-click on the object name or select Edit from
   the pop-up menu.

2. In the
   Open dialog box, select the object type from the Object Type drop-down
   list. Then select the target as well as the library or libraries
   you want to look in. Finally select the object you want to open.

   

   Displaying objects from many libraries To find an object more easily, you can select more than one
   library in the Libraries list. Use Ctrl+Click to select
   additional libraries and Shift+Click to select a range.

3. Click OK.

   The object opens in the appropriate painter.

Accessing recently opened objects

You can quickly open
recently opened objects by selecting File>Recent Objects
from the menu bar. The Recent Objects list includes the eight most recently
opened objects by default, but you can include up to 36 objects
on the list.

To modify the number of recent objects:

1. Select Tools>System Options from
   the menu bar.

2. On the General page of the System Options dialog
   box, modify the number for the recent objects list.

Running or previewing objects

To run a window or preview a DataWindow object, you use the
Run dialog box.

Using the System Tree Instead of using the Run dialog box, you can right-click the
object in the System Tree and select Run/Preview from the
pop-up menu.

To run or preview an object:

1. Do one of the following:

   • Click
     the Run/Preview Object button in the PowerBar.
   • Select File>Run/Preview from the
     menu bar.

2. In
   the Run dialog box, select the object type from the Object Type
   drop-down list.

3. Select the target as well as the library or libraries
   you want to look in.

4. Select the object you want to run or preview and
   click OK.

   The object runs or is previewed.

For more specific information on running a window, see “Running a window”. For
information on using the DataWindow painter’s Preview view,
see Chapter 18, “Defining DataWindow Objects .”

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