Module is.codion.framework.domain
Package is.codion.framework.domain.entity.attribute

Interface Attribute<T>

Type Parameters:
T - the attribute type
All Known Subinterfaces:
Column<T>, ForeignKey
public sealed interface Attribute<T> permits Column<T>, ForeignKey (not exhaustive)
Typed Attribute representing a named, typed property of an entity.

Attributes are the building blocks of entity definitions, representing columns, foreign keys, derived values, or transient properties. Each attribute has a name, type, and is associated with a specific entity type.

Note that attribute names are case-sensitive and Attributes are equal if their names and entityTypes are equal, the attribute value type does not factor into equality.

Attributes are typically created through entity type factory methods and then configured using the as() method to create attribute definitions: 

interface InvoiceLine {
	EntityType TYPE = DOMAIN.entityType("chinook.invoiceline");

	// Typed columns, mapped to table columns
	Column<Long> ID = TYPE.longColumn("id");
	Column<BigDecimal> UNITPRICE = TYPE.bigDecimalColumn("unitprice");
	Column<Integer> QUANTITY = TYPE.integerColumn("quantity");

	// An attribute not mapped to a column, here a derived one
	Attribute<BigDecimal> TOTAL = TYPE.bigDecimalAttribute("total");
}

EntityDefinition invoiceLine() {
	return InvoiceLine.TYPE.as()
					.attributes(
									InvoiceLine.ID.as()
													.primaryKey(),
									InvoiceLine.UNITPRICE.as()
													.column()
													.caption("Price")
													.nullable(false),
									InvoiceLine.QUANTITY.as()
													.column()
													.caption("Quantity")
													.nullable(false)
													.defaultValue(1),
									InvoiceLine.TOTAL.as()
													.derived()
													.from(InvoiceLine.QUANTITY, InvoiceLine.UNITPRICE)
													.with(new InvoiceLineTotal())
													.caption("Total"))
					.build();
}

void attributes(Entities entities) {
	// Usage with entities
	Entity invoiceLine = entities.entity(InvoiceLine.TYPE)
					.with(InvoiceLine.UNITPRICE, BigDecimal.valueOf(0.99))
					.with(InvoiceLine.QUANTITY, 2)
					.build();

	// Type-safe value access
	BigDecimal unitPrice = invoiceLine.get(InvoiceLine.UNITPRICE);
	Integer quantity = invoiceLine.get(InvoiceLine.QUANTITY);
	BigDecimal total = invoiceLine.get(InvoiceLine.TOTAL); // 1.98

	// Attribute type information
	Class<BigDecimal> priceType = InvoiceLine.UNITPRICE.type().get(); // BigDecimal.class
	boolean numeric = InvoiceLine.QUANTITY.type().isNumeric();      // true
	boolean decimal = InvoiceLine.UNITPRICE.type().isDecimal();     // true
}
See Also: