16 Interface-Oriented Programming for Classes

(require unstable/class-iop)

A static interface name is used by the checked method call variants (send/i, send*/i, and send/apply/i). When used as an expression, a static interface name evaluates to an interface value.

Examples:

> (define-interface stack<%> () (empty? push pop)) > stack<%> #<|interface:stack<%>|> > (define stack%     (class* object% (stack<%>)       (define items null)       (define/public (empty?) (null? items))       (define/public (push x) (set! items (cons x items)))       (define/public (pop) (begin (car items) (set! items (cdr items))))       (super-new)))

Use define-interface/dynamic to wrap interfaces from other sources.

Examples:

> (define-interface/dynamic object<%> (class->interface object%) ()) > object<%> #<interface:object%>

The argument static-ifc-id must be defined as a static interface. The method method-id must be a member of the static interface static-ifc-id; otherwise a compile-time error is raised.

The value of obj-expr must be an instance of the interface static-ifc-id; otherwise, a run-time error is raised.

Examples:

> (define s (new stack%)) > (send/i s stack<%> push 1) > (send/i s stack<%> popp) eval:9:0: send/i: method not in static interface   in: popp > (send/i (new object%) stack<%> push 2) send/i: interface check failed on: (object)

Example:

> (send*/i s stack<%>     (push 2)     (pop))

Example:

> (send/apply/i s stack<%> push (list 5))

No dynamic object check is performed when calling a method (using send/i, etc) on a name defined via define/i.

No dynamic object check is performed when calling a method (using send/i, etc) on a name bound via one of these forms. Note that in the case of init-field/i this check omission is unsound in the presence of mutation from outside the class. This should be fixed.

Examples:

> (define-interface-expander stack-methods     (lambda (stx) #'[empty? push pop])) > (define-interface stack<%> ()     ((stack-methods))) > (interface->method-names stack<%>) '(pop push empty?)