Calculated (Property Keyword)
Usage
To specify that the property has no in-memory storage allocated for it, use the following syntax:
Property name As classname [ Calculated ];
Otherwise, omit this keyword or place the word Not immediately before the keyword.
Details
This keyword specifies that the property has no in-memory storage allocated for it when the object containing it is instantiated.
Use this keyword when you are defining a property that does not need any in-memory storage. There are two ways to specify a value for this property:
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Define a Get (and possibly a Set) method for the property. For example, for an Age property, you could provide an AgeGet method that determines a person’s current age based on the current time and the value of their DateOfBirth property. See Using and Overriding Property Methods.
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Define this property as a computed property; this uses the SqlComputed keyword and related keywords. See Defining a Computed Property.
Subclasses inherit the Calculated keyword and cannot override it.
To include a property with the Calculated keyword in an index for a SQL table, you must also specify the SqlComputed and SqlComputeCode keywords as well. If you try to compile the class with an index on a Calculated property, without also specifying the SqlComputed and SqlComputeCode keywords on the property, the system returns the following error message:
ERROR #5414: Invalid index attribute: <classname>::<indexname>::<propertyname>
ERROR #5030: An error occurred while compiling class <classname>
Default
The default value for the Calculated keyword is false.
Example
Property Age as %Integer [ Calculated ];
