Classes and properties

In several applications, it may be necessary to associate alphanumeric information to the model/drawing or parts of the drawing/model (solids, simple entities). For this purpose, the application has non-graphic entities (strings, integers or real numbers) which can be associated to the model/drawing or to component entities: these are the properties (UDP=User Defined Property).

• A property may only exist in relation to an entity of the model/drawing or to the model/drawing itself. If you delete the entities to which the property is associated, you also delete the property.
• You can use the program to create and view the properties associated to the model/drawing or to entities; you can also display the content by inserting symbolic text.
• To use a property, you must specify its characteristics by creating the relative property class (UDC=User Defined Class).
• Several different property classes can be associated to every entity, but only one property of a certain class can be associated to that entity.

This section describes:

• Property classes
• Rules for class names
• Empty classes
• Functioning and commands
• Importing modelsdrawings and properties
• How to display the properties

Property classes

The property class identifies the set of characteristics of the properties to be assigned. A property class is defined by:

• an unambiguous name.
• the type of property (characters, integers, real numbers).
• the maximum number of elements (dimensions).
• the assignability characteristics of the property, that is, the possibility of being assigned to the modeldrawing, to a solid or to a general entity.
• the protections for reading, writing and deleting the class and/or property, once it has been assigned.

The definition of a property class makes it possible to assign properties belonging to the class defined, whose content matches the type specified.

Names of the property classes

The names of the property classes are subject to the following conventions:

• maximum length 128 characters.
• the first character must NOT be a number.
• the rest of the characters may be letters, numbers or the - (minus), _ (underscore) and $ (dollar) characters.

The letters contained in the name are converted by the program to uppercase. Therefore, in all the application output (lists and global variables), the name of a property class or a property is in uppercase.

Empty classes

When there is no property associated to an entity or the modeldrawing for a defined property class, the class is said to be empty. Deletion and some types of modification of a class may only be performed if the class is empty; for example, changing the type of a class when properties are already assigned could cause problems.

Functioning

Association of properties to the modeldrawing or parts of the modeldrawing requires the following:

1. define the corresponding property class.
2. assign the properties by associating them to the modeldrawing or to one or more parts of the modeldrawing and assigning values.

For example, to assign the codes to the parts of a modeldrawing, a "code" class with the appropriate characteristics must be defined (which, in the majority of cases, may be an alphanumeric - string -, which can only be assigned to solids).

The operations for the property and the class require the following commands:

	Create UDC	Defines a new property class
	Modify UDC	Modifies a property class
	Delete UDC	Deletes a property class
	Assign UDP	Assigns a property to an entity or to the modeldrawing
	Modify UDP	Modifies the value of a property already assigned to an entity.
	Delete UDP	Deletes the assigning of a property to an entity

In addition to the above commands, to control UDCs and UDPs of the model/drawing itself, see also:

• How to create a UDC and assign the corresponding UDP to the model/drawing
• How to delete a UDC, removing its assignment from the model/drawing

Importing modelsdrawings and properties

If another modeldrawing contained in a file is imported to the current modeldrawing, the non-empty classes and the relative properties are also imported. The application manages problems of incompatibility between classes with the same name in the current modeldrawing and the modeldrawing you want to import.

Two classes are considered to be incompatible if:

• they have the same name, but are different types.
• they have the same name and are the same type, when the class you want to import has a maximum number of elements which is higher than that in the corresponding class of the current modeldrawing.

In the event of incompatibility, the program automatically modifies the name of the class to be imported, adding a suffix consisting of the "_" character and a sequence number (from 1 to 100).

For example, a Character CODE class is defined in the current modeldrawing. An Integer CODE class is defined in the modeldrawing you want to import. It will be imported with the name CODE_1.

If the properties of the imported modeldrawing have the same name as those in the current modeldrawing but they are not incompatible, the properties imported may be referred to classes which are slightly different from the original ones, in terms of assignability and protections. The values assigned, however, will be maintained.

For example, the C CODE is defined in the current modeldrawing, assignable to all but not to the modeldrawing as a whole. A C CODE is also defined in the modeldrawing to be imported, also assignable to all. After the import, all the CODE properties assigned to any entities of the imported modeldrawing are maintained while any properties assigned to the imported modeldrawing as a whole are lost.

How to display the properties

A set of symbolic notations (see "Symbolic text") can be used within text and dimensions to display the property values.

For example, to display the value of a property assigned to an entity in a label, use the symbolic text $QS{property_name}. If a CODE property is defined, you can add the text $QS{CODE} in the label to display the CODE value:

Similarly, you can use the symbolic text $M{property_name} to display the value of a property assigned to the model/drawing.