▼scramble:   Assorted Utility Libraries
On this page:
init-private
constructor-style-printable<%>
get-printing-class-name
get-printing-components
print-quotable-never<%>
print-quotable-always<%>
about<%>
about
8.16.0.4
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17 Classes and Objects🔗ℹ

 (require scramble/class) package: scramble-lib

syntax

(init-private init-decl ...)

Like init-field, but declares private fields instead of public fields. That is, the fields are declared via define rather than field; the corresponding init-argument names are still externally visible.

Examples:
> (define person%
    (class object%
      (init-field name)
      (init-private [id #f])
      (super-new)))
> (define alice (new person% (name "Alice") (id 1001)))
> (get-field name alice)

"Alice"

> (get-field id alice)

get-field: given object does not have the requested field

  field name: id

  object: (object:person% ...)

interface

constructor-style-printable<%> : interface?

Interface for objects that implement constructor-style printing—that is, as a new expression with the class name and a sequence of initialization arguments (init arguments).
If the object’s state is not representable in terms of its actual init arguments, then consider using printable<%> to implement a printer that does not produce constructor-style output. Or alternatively, also implement the (empty) interface print-quotable-always<%> to force printing in non-expression style.
See also prop:custom-write and make-constructor-style-printer.

method

(send a-constructor-style-printable get-printing-class-name)

 → symbol?
Returns a symbol to be used as the class name when printed.

method

(send a-constructor-style-printable get-printing-components)

 → 
(listof symbol?) (listof any/c) boolean?
Returns (values names values more?), which control the printing of the object’s contents as follows:

The names represent the names of the object’s fields—or more properly, its init arguments. The values are the corresponding values; the two lists should have the same length.

If more? is true, then ... is printed after the initialization arguments to indicate that the object contains additional state not represented by the printed output.

Examples:
> (define friendly-person%
    (class* person% (constructor-style-printable<%>)
      (inherit-field name)
      (super-new)
  
      (define/public (get-printing-class-name)
        'friendly-person%)
      (define/public (get-printing-components)
        (values '(name) (list name) #t))))
> (define bob (new friendly-person% (name "Bob")))
> bob

(new friendly-person% (name "Bob") ...)

> (list bob)

'(#<friendly-person%: (name "Bob") ...>)

> (write bob)

#<friendly-person%: (name "Bob") ...>

interface

print-quotable-never<%> : interface?

This interface contains no methods. It attaches the prop:custom-print-quotable property to objects, with the value 'never.

Examples:
> (define expressive-person%
    (class* friendly-person% (print-quotable-never<%>)
      (super-new)
      (define/override (get-printing-class-name)
        'expressive-person%)))
> (define kristen (new expressive-person% (name "Kristen")))
> kristen

(new expressive-person% (name "Kristen") ...)

> (list kristen)

(list (new expressive-person% (name "Kristen") ...))

> (write kristen)

#<expressive-person%: (name "Kristen") ...>

interface

print-quotable-always<%> : interface?

This interface contains no methods. It attaches the prop:custom-print-quotable property to objects, with the value 'always.

Examples:
> (define obscure-person%
    (class* friendly-person% (print-quotable-always<%>)
      (super-new)
      (define/override (get-printing-class-name)
        'obscure-person%)))
> (define jeff (new obscure-person% (name "Jeff")))
> jeff

'#<obscure-person%: (name "Jeff") ...>

> (list jeff)

'(#<obscure-person%: (name "Jeff") ...>)

> (write jeff)

#<obscure-person%: (name "Jeff") ...>

interface

about<%> : interface?

This interface attaches the prop:about property to objects with an implementation that calls the about method.

method

(send an-about about) → string?

Implements the about operation.

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