▼Unstable
►3 Classes and Objects
On this page:
3.1 Predicates and Contracts
class-or-interface/ c
object-provides/ c
class-provides/ c
mixin-provides/ c
3.2 Mixins
ensure-interface
3.3 Methods
send+
send-each
Version: 5.1
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3 Classes and Objects

Carl Eastlund <cce@racket-lang.org>

 (require unstable/class)

This library is unstable; compatibility will not be maintained. See Unstable for more information.

This module provides tools for classes, objects, and mixins.

3.1 Predicates and Contracts

class-or-interface/c : flat-contract?
Recognizes classes and interfaces.

(object-provides/c spec ...) → flat-contract?
  spec : class-or-interface/c
Recognizes objects which are instances of all the given classes and interfaces.

(class-provides/c spec ...) → flat-contract?
  spec : class-or-interface/c
Recognizes classes which are subclasses (not strictly) and implementations, respectively, of all the given classes and interfaces.

(mixin-provides/c [super-expr ...] [sub-expr ...])
Function contract for a mixin whose argument is the parent class c% matching (class-provides/c super-expr ...) and whose result matches (class-provides/c c% sub-expr ...).

3.2 Mixins

(ensure-interface i<%> mx c%) → (class-provides/c c% i<%>)
  i<%> : interface?
  mx : (mixin-provides/c [] [i<%>])
  c% : class?
Returns c% if it implements i<%>; otherwise, returns (mx c%).

3.3 Methods

(send+ obj [message arg ...] ...)
Sends each message (with arguments) to obj, then returns obj.

Examples:

  (define c%
    (class object%
      (super-new)
      (define/public (say msg) (printf "~a!\n" msg))))
  > (send+ (new c%) [say 'Hello] [say 'Good-bye])

  Hello!

  Good-bye!

  (object:c% ...)

(send-each objs message arg ...)
Sends the message to each object in the list objs, returning (void).

Examples:

  (define c%
    (class object%
      (super-new)
      (init-field msg)
      (define/public (say to) (printf "~a, ~a!\n" msg to))))
  > (send-each
     (list (new c% [msg 'Hello])
           (new c% [msg 'Good-bye]))
     say 'World)

  Hello, World!

  Good-bye, World!

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