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NOTE
C++ Class Frameworks and the Visual Component Model
Some properties use an array as the underlying data member. To illustrate let’s put a memo
component on our blank form. Go to the C++Builder Component Palette, choose the
Standard tab, and click on the Memo button. (The tool tip will tell when you are over the
Memo button.) Now move to the form and click on the form where you want the top-left
corner of the memo to appear. As soon as you place the memo component on the form, the
Object Inspector switches to show you the properties of the component just placed on the
form, in this case a TMemo. Locate the Lines property and click on it. Notice that the property
value contains the text (TStrings) and that there is a little button with an ellipsis (…) to the
right of the property value.
The ellipsis button tells you that this property can be edited by invoking
a property editor dialog box. For an array of strings, for instance, a
dialog box will be displayed in which you can type the strings. In the
case of the Font property, clicking the ellipsis button will invoke the
Choose Font dialog box. The exact type of the property editor is
property specific, although certain properties can share a common
editor. You can bring up the property editor by clicking the ellipsis
button or by double-clicking the property value.
The Lines property for a memo component is an array of strings. When you double-click the
Value column, the string editor is displayed and you can then type the strings you want to
be displayed in the memo component when the application runs. If you don’t want any
strings displayed in the memo component, you will need to clear the property editor of any
strings.
Properties can be instances of other VCL classes. The Font property is an obvious example.
A font includes things like the typeface, the color, the font size, and so on. Locate the Font
property in the Object Inspector. (It doesn’t matter whether you have the memo component
or the form selected.) Notice that there is a plus sign before the word “Font.” This tells you
that there are individual properties within this property that can be set. If you double-click
on the property name, you will see that the Object Inspector expands the property to reveal
the individual elements of that property. You can now edit the elements of the Font property
individually. The same settings can be edited by invoking the Property Editor. Either method
can be used, and in the end the results are the same.
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Some properties are sets, or collections of other properties.
The Style property within the Font object is a good example of a set. Notice that Style has
a plus sign in front of it. If you double-click on the Style property, you will see that the Style
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