LT On-line: Lesson 8

30 Sep, 2000 By: Mark Middlebrook

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:

AutoCAD DatabaseDatabase
block definitiondatabase table structure
block insert one record in the tableone record in the table
attribute definitionfield name
attribute valuevalue of the field in one record

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.

Note: You rarely need to use any of the Mode settings (Invisible, Constant, Verify, or Preset), so just leave them unchecked. If you're curious about what the modes do, use the dialog box Help to find out more.

3. In the Attribute area, type the Tag (database field name), Prompt (user prompt), and Value (default value).
Note: The Tag can't contain any spaces. The Prompt and default Value fields may contain spaces.

4. In the Text Options area, specify the Justification, Text Style, Height, and Rotation.
The text properties for attribute definitions are the same as those for line text objects.

5. Choose the Pick Point button and choose an insertion point for the attribute definition.
An attribute definition's insertion point is like a text string's base point.

6. Click OK to create the attribute definition.

7. Repeat steps 1 through 6 for any additional attribute definitions.

Tip: If you need to create a series of similar attribute definitions, create the first one using steps 1 through 6. Then copy the first attribute definition and edit the copy(s) with the Properties window or the Ddedit command.

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

About the Author: Mark Middlebrook

More News and Resources from Cadalyst Partners

For Mold Designers! Cadalyst has an area of our site focused on technologies and resources specific to the mold design professional. Sponsored by Siemens NX.  Visit the Equipped Mold Designer here!

For Architects! Cadalyst has an area of our site focused on technologies and resources specific to the building design professional. Sponsored by HP.  Visit the Equipped Architect here!