Graphics Programs Reference
In-Depth Information
Using Named Objects
One of the things that can make AutoCAD a tough nut to crack is the somewhat cavalier
naming conventions used in the program's documentation. For years, things like lines,
arcs, and other
graphical
items were called
entities,
but more recently, they started being
called
objects.
Fair enough, but
object
has also long been used to define certain
non-
graphical
components of a drawing — things that you'd hardly consider to be objects at
all — and
those
are the kind of “named objects” I describe in what follows.
Hidden in the innards of every AutoCAD drawing file is a set of
named objects.
Named objects are organized into
symbol tables,
and the properties that are com-
mon to all AutoCAD objects are defined in these tables. For example, all the line
objects in a drawing are stored on one or more layers, so a layer property is com-
mon to all lines and is defined in the layer table. But the coordinates that define
the start and end points of a given line are unique to that line (or they should be!)
— so the coordinate properties are
not
common to all lines.
Layers are one example of a named object. The layer table in a given drawing contains a
list of the layers in the current drawing, along with the settings for each layer (color,
linetype, on/off setting, and so on).
Named objects don't appear as graphical objects in your drawing. They're like the hard-
working pit crew that keeps the race cars running smoothly behind the scenes. The
named objects you're likely to use the most include
Layers (covered in the section “Putting it on a layer,” earlier in this chapter)
Linetypes (covered in the section “Accumulating properties,” earlier in this
chapter)
Text styles (see Chapter 13)
Table styles (see Chapter 13)
Multileader styles (see Chapter 13)
Multiline styles (not covered in this topic; see the online help)
Dimension styles (see Chapter 14)
Block definitions and xrefs (see Chapters 17 and 18)
