function getDisplayName(currentState) {
                        var interpolationContext;
                        var propertyReference;
                        var displayName;

                        if (!scope.displaynameProperty) {
                            // if the displayname-property attribute was not specified, default to the state's name
                            return currentState.name;
                        }
                        propertyReference = getObjectValue(scope.displaynameProperty, currentState);

                        if (propertyReference === false) {
                            return false;
                        } else if (typeof propertyReference === 'undefined') {
                            return currentState.name;
                        } else {
                            // use the $interpolate service to handle any bindings in the propertyReference string.
                            interpolationContext =  (typeof currentState.locals !== 'undefined') ? currentState.locals.globals : currentState;
                            displayName = $interpolate(propertyReference)(interpolationContext);
                            return displayName;
                        }
                    }
Resolve the displayName of the specified state. Take the property specified by the `displayname-property`
attribute and look up the corresponding property on the state's config object. The specified string can be interpolated against any resolved
properties on the state config object, by using the usual {{ }} syntax.
@param currentState
@returns {*}