(Quick Reference)
discriminator
Purpose
Customizes the discriminator column used in table-per-hierarchy inheritance mapping. Has no effect when using table-per-subclass inheritance mapping.
Examples
class PodCast extends Content {
…
static mapping = {
discriminator "audio"
}
}Description
Usage:
discriminator(string/map)Arguments:
column (optional) - The column name to store the discriminatorvalue - The value to use for the discriminatorformula (optional) - an SQL expression that is executed to evaluate the type of class. Use this or column but not bothtype (optional defaults to string) - the Hibernate type, used for the where clause condition to know if it needs to wrap it with '
By default when mapping inheritance Grails uses a single-table model where all classes share the same table. A discriminator column is used to determine the type for each row, by default the full class name. You can use the
discriminator method to customize what's stored:
class PodCast extends Content {
…
static mapping = {
discriminator "audio"
}
}You can also customize the discriminator column name:
class Content {
…
static mapping = {
discriminator column: "content_type"
}
}class PodCast extends Content {
…
static mapping = {
discriminator value: "audio"
}
}Or you can use a formula:
class Content {
…
static mapping = {
discriminator value: "1", type: "integer",
formula: "case when CLASS_TYPE in ('a', 'b', 'c') then 0 else 1 end",
}
}class PodCast extends Content {
…
static mapping = {
discriminator value: "0"
}
}
