5.11 Object, Class, and Interface Utilities

► |  | Reference: Racket

1 | Language Model
2 | Syntactic Forms
3 | Datatypes
4 | Structures
5 | Classes and Objects
6 | Units
7 | Contracts
8 | Pattern Matching
9 | Control Flow
10 | Concurrency
11 | Macros
12 | Input and Output
13 | Reflection and Security
14 | Operating System
15 | Memory Management
16 | Unsafe Operations
17 | Running Racket
| Bibliography
| Index

▼ | 5 | Classes and Objects

5.1 | Creating Interfaces
5.2 | Creating Classes
5.3 | Creating Objects
5.4 | Field and Method Access
5.5 | Mixins
5.6 | Traits
5.7 | Object and Class Contracts
5.8 | Object Equality and Hashing
5.9 | Object Serialization
5.10 | Object Printing
5.11 | Object, Class, and Interface Utilities
5.12 | Surrogates

On this page:

object?
class?
interface?
generic?
object=?
object->vector
class->interface
object-interface
is-a?
subclass?
implementation?
interface-extension?
method-in-interface?
interface->method-names
object-method-arity-includes?
field-names
object-info
class-info
exn: fail: object

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#### 5.11`` Object, Class, and Interface Utilities

( object? v) → boolean?
v : any/c

Returns #t if v is an object, #f otherwise.

( class? v) → boolean?
v : any/c

Returns #t if v is a class, #f otherwise.

( interface? v) → boolean?
v : any/c

Returns #t if v is an interface, #f otherwise.

( generic? v) → boolean?
v : any/c

Returns #t if v is a generic, #f otherwise.

( object=? a b) → boolean?
a : object?
b : object?

Determines if two objects are the same object, or not; this procedure uses eq?, but also works properly with contracts.

( object->vector object [opaque-v]) → vector?
object : object?
opaque-v : any/c = #f

Returns a vector representing object that shows its inspectable fields, analogous to struct->vector.

( class->interface class) → interface?
class : class?

Returns the interface implicitly defined by class.

( object-interface object) → interface?
object : object?

Returns the interface implicitly defined by the class of object.

( is-a? v type) → boolean?
v : any/c
type : ( or/c interface? class?)

Returns #t if v is an instance of a class type or a class that implements an interface type, #f otherwise.

( subclass? v class) → boolean?
v : any/c
class : class?

Returns #t if v is a class derived from (or equal to) class, #f otherwise.

( implementation? v interface) → boolean?
v : any/c
interface : interface?

Returns #t if v is a class that implements interface, #f otherwise.

( interface-extension? v interface) → boolean?
v : any/c
interface : interface?

Returns #t if v is an interface that extends interface, #f otherwise.

( method-in-interface? sym interface) → boolean?
sym : symbol?
interface : interface?

Returns #t if interface (or any of its ancestor interfaces) includes a member with the name sym, #f otherwise.

( interface->method-names interface) → ( listof symbol?)
interface : interface?

Returns a list of symbols for the method names in interface, including methods inherited from superinterfaces, but not including methods whose names are local (i.e., declared with define-local-member-names).

( object-method-arity-includes? |  | object |  |  |  |
|  | sym |  |  |  |
|  | cnt) |  | → |  | boolean?

object : object?
sym : symbol?
cnt : exact-nonnegative-integer?

Returns #t if object has a method named sym that accepts cnt arguments, #f otherwise.

( field-names object) → ( listof symbol?)
object : object?

Returns a list of all of the names of the fields bound in object, including fields inherited from superinterfaces, but not including fields whose names are local (i.e., declared with define-local-member-names).

( object-info object)

→

( or/c class? #f) |  | boolean?

object : any/c

Returns two values, analogous to the return values of struct-info:

- class: a class or #f; the result is #f if the current inspector does not control any class for which the object is an instance.

- skipped?: #f if the first result corresponds to the most specific class of object, #t otherwise.

( class-info class)

→

symbol?
exact-nonnegative-integer?
( listof symbol?)
( any/c exact-nonnegative-integer? . -> . any/c)
( any/c exact-nonnegative-integer? any/c . -> . any/c)
( or/c class? #f)
boolean?

class : class?

Returns seven values, analogous to the return values of struct-type-info:

- name: the class’s name as a symbol;

- field-cnt: the number of fields (public and private) defined by the class;

- field-name-list: a list of symbols corresponding to the class’s public fields; this list can be larger than field-k because it includes inherited fields;

- field-accessor: an accessor procedure for obtaining field values in instances of the class; the accessor takes an instance and a field index between 0 (inclusive) and field-cnt (exclusive);

- field-mutator: a mutator procedure for modifying field values in instances of the class; the mutator takes an instance, a field index between 0 (inclusive) and field-cnt (exclusive), and a new field value;

- super-class: a class for the most specific ancestor of the given class that is controlled by the current inspector, or #f if no ancestor is controlled by the current inspector;

- skipped?: #f if the sixth result is the most specific ancestor class, #t otherwise.

( struct |  | exn:fail:object exn:fail ()
|  | #:extra-constructor-name make-exn:fail:object)

Raised for class-related failures, such as attempting to call a method that is not supplied by an object.
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