SQT_COLUMN_CUSTOM

#define SQT_COLUMN_CUSTOM	(		COLUMN_NAME,
			VALUE_SOURCE )

Defines a column that binds to the specified custom value source.

Parameters

COLUMN_NAME	The name of the column in the database. It will be also used as the instance name of the column.
VALUE_SOURCE	A type that satisfies the sqt::ValueSourceType concept, which defines the value type and methods for retrieving and setting values in an entity instance.

This macro is similar to SQT_COLUMN_FIELD, except that it binds to a custom value source. It is useful if the column value is not directly accessible through a field or accessor methods. For example, the column value may be derived from multiple fields or requires some computation or transformation before getting or setting it.

The sqt::ValueSourceType concept specifies the interface that a value source must implement:

• The value type for the column.
• Methods to retrieve and set the value in an entity instance.

Example usage:

struct MyEntity {
    int id{};
    std::string name;
};
 
// Define the value source type for the ID column.
struct IDValueSource {
    using ValueType = int;
    static int GetValueFromEntity(const MyEntity& entity) {
        return entity.id;
    }
    static void SetValueToEntity(MyEntity& entity, int value) {
        entity.id = value;
    }
};
 
SQT_TABLE_BEGIN(MyEntityTable, MyEntity)
 
// Define the ID column with the custom value source.
SQT_COLUMN_CUSTOM(ID, IDValueSource)
 
// Define the Name column with an inline custom value source.
SQT_COLUMN_CUSTOM(Name, struct NameValueSource {
    using ValueType = std::string;
    static const std::string& GetValueFromEntity(const MyEntity& entity) {
        return entity.name;
    }
    static void SetValueToEntity(MyEntity& entity, std::string value) {
        entity.name = std::move(value);
    }
})
 
SQT_TABLE_END

See also

sqt::ValueSourceType

SQT_COLUMN_CUSTOM_2

SQT_COLUMN_FIELD