Understanding the Write Block Dialog Box Options

Understanding the Write Block Dialog Box Options
The Write Block dialog box offers a way to save parts of your current drawing as a file. As you can
see from the dialog box shown in the previous exercise, you have several options.
In that exercise, you used the Block option of the Source group to select an existing block as the
source object to be exported. You can also export a set of objects by choosing the Objects option. If
you choose this option, the Base Point and Objects groups become available. These options work
the same way as their counterparts in the Block Definition dialog box, which you saw earlier when
you created the Tub and Toilet blocks.
The other option in the Source group, Entire Drawing, lets you export the whole drawing to
its own file. This may seem to duplicate the File  Save As option in the menu bar, but saving the
entire drawing from the Write Block dialog box performs some additional operations, such as stripping
out unused blocks or other unused components. This has the effect of reducing file size. You’ll
learn more about this feature later in this chapter.

Other Uses for Blocks
So far, you’ve used the Make Block tool to create symbols, and you’ve used the Export and Wblock
commands to save those symbols to disk. As you can see, you can create symbols and save them at
any time while you’re drawing. You’ve made the tub and toilet symbols into drawing files that you
can see when you check the contents of your current folder.
However, creating symbols isn’t the only use for the Make Block, Block, Export, and Wblock
commands. You can use them in any situation that requires grouping objects (though you may prefer
to use the more flexible Object Group command discussed later in this chapter). You can also use
blocks to stretch a set of objects along one axis by using the Properties palette. Export and Wblock
also enable you to save a part of a drawing to disk. You’ll see instances of these other uses of the
Block, Export, and Wblock commands throughout the book.
Make Block, Export, and Wblock are extremely versatile commands and, if used judiciously, can
boost your productivity and simplify your work. If you aren’t careful, however, you can get carried
away and create more blocks than you can keep track of. Planning your drawings helps you determine
which elements will work best as blocks and recognize situations in which other methods of
organization are more suitable.
Another way of using symbols is to use AutoCAD’s external reference capabilities. External reference
files, known as Xrefs, are files inserted into a drawing in a way similar to blocks. The difference
is that Xrefs don’t become part of the drawing’s database. Instead, they’re loaded along with
the current file at startup time. It’s as if AutoCAD opens several drawings at once: the main file you
specify when you start AutoCAD, and the Xrefs associated with the main file.
By keeping the Xrefs independent from the current file, you make sure that any changes made to
the Xrefs automatically appear in the current file. You don’t have to update each inserted copy of an
Xref. For example, if you use the External References option on the Reference toolbar (discussed in
Chapter 7) to insert the Tub drawing, and later you make changes to the tub, the next time you open
the Bath file, you’ll see the new version of the tub. Or, if you have both the tub and the referencing
drawing open, and you change the tub, AutoCAD will notify you that a change has been made to an
external reference. You can then update the tub Xref using the External Reference palette.
Xrefs are especially useful in workgroup environments, where several people are working on
the same project. One person might be updating several files that have been inserted into a variety
of other files. Before Xrefs were available, everyone in the workgroup had to be notified of the
changes and had to update all the affected blocks in all the drawings that contained them. With
Xrefs, the updating is automatic. Many other features are unique to these files; they’re discussed in
more detail in Chapters 7 and 12.