Using Caché Objects - InterSystems Documentation

Operation
11.2 Operation
This section describes the basic features and functionality of Caché data types.
11.2.1 Using Data Types in Classes
The principal function of data type classes is for specifying the types of properties within a
class. The basic definition format is:
Property City As %String;
Because data types are part of the %Library package, you can simply call them without
explicitly mentioning the package name.
11.2.1.1 Validation Functionality
Any property using a system data type (or a data type derived from a system data type) supports
data validation through a generated method associated with the property. The validation
method has a name of the form PropertyNameIsValidDT; for instance, an Age property of
type %Integer has an associated AgeIsValidDT method. The method checks the validity of
a value specified for the property.
11.2.2 Parameters
Data type classes support various parameters. These perform various actions and vary from
data type to data type. These parameters include:
• COLLATION — Specifies the manner in which property values are transformed for
indexing.
The allowable values for collation are discussed in the SQL Introduction.
• DISPLAYLIST — Used in conjunction with the VALUELIST parameter for enumerated
(multiple-choice) properties. DISPLAYLIST, if not null, represents the display values
for the property corresponding with the logical values listed in VALUELIST. The display
values are returned by the LogicalToDisplay method.
• FORMAT — Specifies the format for the data type's display value. The value of FORMAT
corresponds to the formatting option of the $FNUMBER function, which performs the
formatting.
Using Caché Objects 91