Getting Started

Parts

In VisualAge, a part is a self-contained software object with a well-defined public interface that establishes the features of the part.

There are three types of parts that you work with in VisualAge:

Visual part
A part that has a visual appearance at run time. Visual parts, such as windows, push buttons, and entry fields, make up the user interface of an application. Visual parts can contain other visual parts, nonvisual parts, connections to other parts and IBM Smalltalk code. The Composition Editor is the primary tool used to create and modify visual parts.

Nonvisual part
A part that has no visual appearance at run time. A nonvisual part typically represents behaviors or data within an application. Nonvisual parts can contain other nonvisual parts, connections to other parts and IBM Smalltalk code. The Composition Editor is the primary tool used to create and modify nonvisual parts.

Smalltalk class
A Smalltalk class and associated methods may be used to implement behavior or represent data directly through the use of the IBM Smalltalk language. The Script Editor is the primary tool used to create and modify Smalltalk classes.

A part's public interface determines how it can interact with other parts. The public interface of a part consists of the following types of features:

Attributes
Data that can be accessed by other parts. This data can represent any logical property of a part, such as the balance of an account, the size of a shipment, or the label of a push button.

Events
Signals that indicate something has happened, such as opening a window or changing an attribute's value.

Actions
Operations or functions that a part can perform. Actions can be triggered by connections from other parts.

Parts placed inside of other parts are called subparts. A part that contains other parts is called a composite part. All parts can be reused as subparts of composite parts.


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