LT On-line: Lesson 8

Fill-in-the Blank Blocks: Attributes

Page 1: Introduction to attributes

My previous two LT Online tutorials covered most of the ins and outs of defining, inserting, and updating blocks. However, before you can consider yourself a block master (not to be confused with a blockhead), you need to know how to use attributes in blocks and purge your drawings of unused block definitions.

The procedures described here work with AutoCAD LT 2000 and 98 and AutoCAD 2000 and Release 14.

About attributes
Attributes are fill-in-the-blank text fields that you can add to your blocks. When you create a block definition and then insert it several times in a drawing, all of the ordinary geometry (lines, circles, regular text strings, and so on) in all of the instances is exactly identical. Attributes provide a little more flexibility in the form of text strings that can be different in each block insert.

For example, suppose that you frequently designate parts in your drawings by labeling them with a number or letter in a circle, as shown in figure 1 below.

Figure 1.

If you want to create a block for this symbol, you can't simply draw the number or letter as regular text using the Text or Mtext command. If you create a block definition with a regular text object (e.g., the letter A), the text string is the same in every instance of the block (e.g., always the letter A).

Instead, you create an attribute definition, which acts as a place holder for a text string that can vary each time you insert the block. You include the attribute definition when you create the block definition, as described in tutorial #6: "Make and use blocks". Then, each time you insert the block, AutoCAD prompts you to fill in an attribute value for each attribute definition.

If you've worked with databases, these correspondences between attributes and database terminology might help you understand the concept:

One of the most common uses for attributes is in title blocks. Tutorial #2 demonstrates how to use fill-in-the-blank attributes to make filling out title block text easier.

How to create attribute definitions
You use the Attribute Definition dialog box to create attribute definitions. The procedure is similar to creating a text string, except that you must supply a little more information.
1. Change to the layer on which you want to create the attribute definition.

2. Choose Draw, Block, Define Attributes to run the Attdef command (Ddattdef in AutoCAD Release 14 and LT 98), which displays the Attribute Definition dialog box, as shown in figure 2.

Figure 2.

Fill-in-the Blank Blocks: Attributes
  Page 1: Introduction to attributes
  Page 2: How to transfer blocks between drawings
  Page 3: Redefine blocks