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VCL Components
C++Builder displays an icon representing the component on the form. This icon is used to
access the component at design time in order to change the component’s properties, but the
icon does not show up when the program runs. Nonvisual components have properties,
methods, and events just like visual components do.
The Name Property
NOTE
The Name property serves a vital role in components. As mentioned earlier, when you place
a component on a form, C++Builder goes to work in the background while you ponder your
next move. One thing C++Builder does is create a pointer to the component and assign the
Name property as the variable name. For example, let’s say you place an Edit component on
a form and change the Name property to MyEdit. At that point C++Builder places the following
in the header file for the form:
TEdit* MyEdit;
When the application runs, C++Builder creates an instance of the TEdit class and assigns it
to MyEdit. You can use this pointer to access the component at runtime. To set the text for
the edit control, you would use
MyEdit->Text = “Jenna Lynn”;
C++Builder also uses the Name property when creating event handler names. Let’s say that you
wanted to respond to the OnChange event for an Edit component. Normally, you double-click
the Value column next to the OnChange event to have C++Builder generate an event handler
for the event. C++Builder creates a default function name based on the Name property of the
component and the event being handled. In this case, C++Builder would generate a function
called MyEditChange().
You can change the Name property at any time, provided that you change it only via the Object
Inspector. When you change a component’s Name property at design time, C++Builder goes
through all the code that C++Builder had previously generated and changes the name of the
pointer and all event-handling functions.
C++Builder will change all the code generated by C++Builder to reflect
the new value of the component’s Name property, but it will not modify
any code you wrote. In other words, C++Builder will take care of
modifying the code it wrote, but it is up to you to update and maintain
the code you wrote. Generally speaking, you should change the Name
property when you initially place the component on the form and leave
it alone after that.
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