eIsSet

eIsSet is a method in the Eclipse Modeling Framework (EMF) used to determine whether a feature of an EObject is considered set. It is part of the reflective and generated API that allows clients to query the state of model features at runtime, independently of the feature’s type or position.

In EMF, eIsSet can be invoked in a couple of ways. The most common form is eIsSet(int featureID), where featureID identifies a feature defined in the model’s generated package. Some reflective usage may also involve checking a feature via its structural representation. The behavior of eIsSet depends on how the feature is defined in the Ecore model.

For features that are not unsettable, eIsSet returns true when the feature’s current value differs from its default value, and false when the value is equal to the default (with null treated as a default where applicable). For features marked as unsettable, the generated code tracks an explicit set/unset state via an internal flag (often named something like featureESet). In this case, eIsSet returns true if the feature has been explicitly set, and false if the feature is in its unset state.

eIsSet is commonly used in serialization decisions, validation logic, and change notification. It helps determine whether a value should be serialized or persisted, and it interacts with methods such as eGet, eSet, and eUnset to manage feature state. It is part of EMF’s dynamic access pattern, where model behavior can be driven by feature identifiers rather than concrete Java fields.