db4o |

# Evaluation Interface

for implementation of callback evaluations.

For a list of all members of this type, see Evaluation Members.

public interface Evaluation : Serializable

#### Remarks

for implementation of callback evaluations.
To constrain a com.db4o.query.Query node with your own callback

    Evaluation

, construct an object that implements the

    Evaluation

interface and register it by passing it to com.db4o.query.Query.Constrain .
Evaluations are called as the last step during query execution, after all other constraints have been applied. Evaluations in higher level com.db4o.query.Query nodes in the query graph are called first.
Java client/server only:
db4o first attempts to use Java Serialization to allow to pass final variables to the server. Please make sure that all variables that are used within the evaluate() method are Serializable. This may include the class an anonymous Evaluation object is created in. If db4o is not successful at using Serialization, the Evaluation is transported to the server in a db4o MemoryFile. In this case final variables can not be restored.

#### Requirements

Namespace: com.db4o.query

Assembly: db4o (in db4o.dll)

#### See Also

Evaluation Members | com.db4o.query Namespace