} else if(property instanceof EORelationship) {
entity = ((EORelationship)property).entity();
} else {
throw new IllegalArgumentException("property must be an EOAttribute or an EORelationship.");
}
NSArray<EOProperty> classProperties = entity.classProperties();
if(isClassProperty && !classProperties.contains(property)) {
classProperties = classProperties.arrayByAddingObject(property);
entity.setClassProperties(classProperties);
} else if(!isClassProperty && classProperties.contains(property)) {
classProperties = ERXArrayUtilities.arrayMinusObject(classProperties, property);