gtk:drop-down-expression (object)

object -- a gtk:drop-down widget
expression -- a gtk:expression object, or the NULL pointer

The accessor for the expression slot gets or sets the expression that gets evaluated to obtain strings from items when searching in the popup. The expression must have a value of "gchararray" type. The expression is represented as a foreign pointer. Use the (cffi:null-pointer) function to retrieve the NULL pointer representation.