Inheritance/Multiple
You are encouraged to solve this task according to the task description, using any language you may know.
Multiple inheritance allows to specify that one class is a subclass of several other classes. Some languages allow multiple inheritance for arbitrary classes, others restrict it to interfaces, some don't allow it at all.
Write two classes (or interfaces) Camera and MobilePhone, then write a class CameraPhone which is both a Camera and a MobilePhone.
There is no need to implement any functions for those classes.
Ada
Ada 2005 has added interfaces, allowing a limited form of multiple inheritance. <lang ada>package Multiple_Interfaces is
type Camera is tagged null record; type Mobile_Phone is limited Interface; type Camera_Phone is new Camera and Mobile_Phone with null record;
end Multiple_Interfaces;</lang>
Aikido
Aikido does not support multiple inheritance, but does allow multiple implementation of interfaces. <lang aikido>interface Camera { }
interface Mobile_Phone { }
class Camera_Phone implements Camera, Mobile_Phone { }</lang>
BBC BASIC
<lang bbcbasic> INSTALL @lib$+"CLASSLIB"
DIM Camera{TakePicture}
PROC_class(Camera{})
DIM MobilePhone{MakeCall}
PROC_class(MobilePhone{})
DIM CameraPhone{methods}
PROC_inherit(CameraPhone{}, Camera{})
PROC_inherit(CameraPhone{}, MobilePhone{})
PROC_class(CameraPhone{})</lang>
C
C simulates Multiple Inheritance via Structures. <lang C> typedef struct{ double focalLength; double resolution; double memory; }Camera;
typedef struct{ double balance; double batteryLevel; char** contacts; }Phone;
typedef struct{ Camera cameraSample; Phone phoneSample; }CameraPhone; </lang>
C++
<lang cpp>class Camera {
// ...
};
class MobilePhone {
// ...
};
class CameraPhone:
public Camera, public MobilePhone
{
// ...
};</lang>
C#
In C# you may inherit from only one class, but you can inherit from multiple interfaces. Also, in C# it is standard practice to start all interface names with a capital 'I' so I have altered the name of the interface. In the example we inherit from a class and an interface.
<lang csharp>interface ICamera {
// ...
}
class MobilePhone {
// ...
}
class CameraPhone: ICamera, MobilePhone {
// ...
}</lang>
Clojure
<lang Clojure>(defprotocol Camera)
(defprotocol MobilePhone)
(deftype CameraPhone []
Camera MobilePhone)</lang>
COBOL
<lang cobol> CLASS-ID. Camera.
*> ...
END CLASS Camera.
CLASS-ID. Mobile-Phone.
*> ...
END CLASS Mobile-Phone.
CLASS-ID. Camera-Phone INHERITS Camera, Mobile-Phone.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
REPOSITORY.
CLASS Camera
CLASS Mobile-Phone.
*> ...
END CLASS Camera-Phone.</lang>
Common Lisp
<lang lisp>(defclass camera () ()) (defclass mobile-phone () ()) (defclass camera-phone (camera mobile-phone) ())</lang>
D
While D does not have multiple base class inheritance, you can inherit from multiple interfaces.
<lang d>interface Camera {
// member function prototypes and static methods
}
interface MobilePhone {
// member function prototypes and static methods
}
class CameraPhone: Camera, MobilePhone {
// member function implementations for Camera, // MobilePhone, and CameraPhone
}</lang>
D also supports the non-virtual interface pattern, where an interface may have non-virtual methods with defined implementations.
<lang d>interface Camera {
// A virtual function. Image takePhoto();
// A non-virtual function.
final Image[] takeSeveralPhotos(int count) {
auto result = new Image[count];
foreach (ref img; result) {
img = takePhoto();
}
}
}</lang>
In addition, D's alias this feature allows one to create a type that, while it does not technically derive from two different classes, behaves as if it did.
<lang d>class A {
string foo() {
return "I am an A.";
}
} class B {
string foo() {
return "I am a B.";
}
}
class C : A {
string className = "C";
override string foo() {
return "I am a "~className~", and thus an A.";
}
@property
BWrapper asB() {
return new BWrapper();
}
alias asB this;
class BWrapper : B {
override string foo() {
return "I am a "~className~", disguised as a B.";
}
}
}
unittest {
import std.stdio : writeln; auto c = new C(); A a = c; B b = c; writeln(a.foo()); writeln(b.foo());
}</lang>
You can currently only have a single alias this, but multiple alias this is planned. Nested alias this works today, but is somewhat finicky.
Lastly, D has template and string mixins. These can be used for static polymorphism, where a piece of code is written once and has a single definition, but is used in multiple places. It does not enable any sort of dynamic polymorphism that is not covered above.
<lang d>template registerable() {
void register() { /* implementation */ }
}
string makeFunction(string s) {
return `string `~s~`(){ return "`~s~`";}`;
}
class Foo {
mixin registerable!();
mixin(makeFunction("myFunction"));
}
unittest {
import std.stdio : writeln; Foo foo = new Foo; foo.register(); writeln(foo.myFunction());
}</lang>
Using D's CTFE and reflection capabilities, string mixins can copy the interface of other types, and thus be used for proxies and mocks.
Delphi
Delphi doesn't support multiple inheritance, but it does have multiple interfaces.
<lang Delphi>type
ICamera = Interface // ICamera methods... end;
IMobilePhone = Interface // IMobilePhone methods... end;
TCameraPhone = class(TInterfacedObject, ICamera, IMobilePhone) // ICamera and IMobilePhone methods... end;</lang>
DWScript
See Delphi.
E
E does not have multiple inheritance as a built-in feature. In fact, E only has inheritance at all as a light syntactic sugar over delegation (message forwarding). However, using that facility it is possible to implement multiple inheritance.
This is a quick simple implementation of multiple inheritance. It simply searches (depth-first and inefficiently) the inheritance tree for a method; it does not do anything about diamond inheritance. These shortcomings could be fixed if more powerful multiple inheritance were needed.
<lang e>def minherit(self, supers) {
def forwarder match [verb, args] {
escape __return {
if (verb == "__respondsTo") {
def [verb, arity] := args
for super ? (super.__respondsTo(verb, arity)) in supers {
return true
}
return false
} else if (verb == "__getAllegedType") {
# XXX not a complete implementation
return supers[0].__getAllegedType()
} else {
def arity := args.size()
for super ? (super.__respondsTo(verb, arity)) in supers {
return E.call(super, verb, args)
}
throw(`No parent of $self responds to $verb/$arity`)
}
}
}
return forwarder
}</lang>
The task example:
<lang e>def makeCamera(self) {
return def camera extends minherit(self, []) {
to takesPictures() { return true }
}
}
def makeMobilePhone(self) {
return def mobilePhone extends minherit(self, []) {
to makesCalls() { return true }
to internalMemory() { return 64*1024 }
}
}
def makeCameraPhone(self) {
return def cameraPhone extends minherit(self, [
makeCamera(self),
makeMobilePhone(self),
]) {
to internalMemory() {
return super.internalMemory() + 32 * 1024**2
}
}
}</lang>
And testing that it works as intended:
<lang e> ? def p := makeCameraPhone(p) > [p.takesPictures(), p.makesCalls(), p.internalMemory()]
- value: [true, true, 33619968]</lang>
Eiffel
Having two class—one for CAMERA and the other for a MOBILE_PHONE ... <lang eiffel >class
CAMERA
end</lang> <lang eiffel >class
MOBILE_PHONE
end</lang>
Now Multiple Inherit
We can create a new CAMERA_PHONE, which inherits directly from both CAMERA and MOBILE_PHONE. <lang eiffel >class
CAMERA_PHONE
inherit
CAMERA MOBILE_PHONE
end</lang> NOTE: There is no reasonable limit to the number of classes we can inherit from in a single class. The compiler helps us to navigate issues like repeated inheritance and the "diamond of death" easily and quickly.
Elena
ELENA only permits inheritance from one parent class. However, mixins are supported <lang elena>singleton CameraFeature {
cameraMsg
= "camera";
}
class MobilePhone {
mobileMsg
= "phone";
}
class CameraPhone : MobilePhone {
dispatch() => CameraFeature;
}
public program() {
var cp := new CameraPhone(); console.writeLine(cp.cameraMsg); console.writeLine(cp.mobileMsg)
}</lang> Alternatively a group object may be created <lang elena>import system'dynamic;
class CameraFeature {
cameraMsg
= "camera";
}
class MobilePhone {
mobileMsg
= "phone";
}
singleton CameraPhone {
new() = new MobilePhone().mixInto(new CameraFeature());
}
public program() {
var cp := CameraPhone.new();
console.writeLine(cp.cameraMsg); console.writeLine(cp.mobileMsg)
}</lang>
Factor
<lang factor>TUPLE: camera ; TUPLE: mobile-phone ; UNION: camera-phone camera mobile-phone ;</lang>
Fantom
Fantom only permits inheritance from one parent class. However, Fantom supports 'mixins': a mixin is a collection of implemented methods to be added to the child class. Any number of mixins can be added to any given child class. It is an error for method names to conflict.
<lang fantom>// a regular class class Camera {
Str cameraMsg ()
{
"camera"
}
}
// a mixin can only contain methods mixin MobilePhone {
Str mobileMsg ()
{
"mobile phone"
}
}
// class inherits from Camera, and mixes in the methods from MobilePhone class CameraPhone : Camera, MobilePhone { }
class Main {
public static Void main ()
{
cp := CameraPhone ()
echo (cp.cameraMsg)
echo (cp.mobileMsg)
}
}</lang>
FreeBASIC
<lang freebasic>' FB 1.05.0 Win64
' FB does not currently support multiple inheritance. Composition has to be used instead if one wants ' to (effectively) inherit from more than one class. In some cases, this might arguably be a better ' solution anyway.
Type Camera Extends Object ' if virtual methods etc needed
' ...
End Type
Type Phone Extends Object
' ...
End Type
Type CameraPhone Extends Phone ' single inheritance
cam As Camera ' using composition here ' other stuff
End Type</lang>
F#
A class can only inherit from one other class, but it can implement any number of interfaces.
<lang fsharp>type Picture = System.Drawing.Bitmap // (a type synonym)
// an interface type type Camera =
abstract takePicture : unit -> Picture
// an interface that inherits multiple interfaces type Camera2 =
inherits System.ComponentModel.INotifyPropertyChanged inherits Camera
// a class with an abstract method with a default implementation // (usually called a virtual method) type MobilePhone() =
abstract makeCall : int[] -> unit default x.makeCall(number) = () // empty impl
// a class that inherits from another class and implements an interface type CameraPhone() =
inherit MobilePhone() interface Camera with member x.takePicture() = new Picture(10, 10)</lang>
Go
Go abandons traditional object oriented concepts of inheritance hierarchies, yet it does have features for composing both structs and interfaces. <lang go>// Example of composition of anonymous structs package main
import "fmt"
// Two ordinary structs type camera struct {
optics, sensor string
}
type mobilePhone struct {
sim, firmware string
}
// Fields are anonymous because only the type is listed. // Also called an embedded field. type cameraPhone struct {
camera mobilePhone
}
func main() {
// Struct literals must still reflect the nested structure
htc := cameraPhone{camera{optics: "zoom"}, mobilePhone{firmware: "3.14"}}
// But fields of anonymous structs can be referenced without qualification. // This provides some effect of the two parent structs being merged, as // with multiple inheritance in some other programming languages. htc.sim = "XYZ" fmt.Println(htc)
}</lang>
- Output:
(Note sensor field still blank)
{{zoom } {XYZ 3.14}}
<lang go>// Example of composition of interfaces. // Types implement interfaces simply by implementing functions. // The type does not explicitly declare the interfaces it implements. package main
import "fmt"
// Two interfaces. type camera interface {
photo()
}
type mobilePhone interface {
call()
}
// Compose interfaces. cameraPhone interface now contains whatever // methods are in camera and mobilePhone. type cameraPhone interface {
camera mobilePhone
}
// User defined type. type htc int
// Once the htc type has this method defined on it, it automatically satisfies // the camera interface. func (htc) photo() {
fmt.Println("snap")
}
// And then with this additional method defined, it now satisfies both the // mobilePhone and cameraPhone interfaces. func (htc) call() {
fmt.Println("omg!")
}
func main() {
// type of i is the composed interface. The assignment only compiles // because static type htc satisfies the interface cameraPhone. var i cameraPhone = new(htc) // interface functions can be called without reference to the // underlying type. i.photo() i.call()
}</lang>
- Output:
snap omg!
Groovy
Same inheritance rules as Java.
Haskell
<lang haskell>class Camera a class MobilePhone a class (Camera a, MobilePhone a) => CameraPhone a</lang>
Icon and Unicon
Icon does not support classes or inheritance. An intermediate language called Idol was developed as proof of concept for extending Icon. This became one of the major addons contributing to Unicon.
<lang unicon>class Camera (instanceVars)
# methods... # initializer...
end
class Phone (instanceVars)
# methods... # initializer...
end
class CameraPhone : Camera, Phone (instanceVars)
# methods... # initialiser...
end</lang>
Io
<lang Io>Camera := Object clone Camera click := method("Taking snapshot" println)
MobilePhone := Object clone MobilePhone call := method("Calling home" println)
CameraPhone := Camera clone CameraPhone appendProto(MobilePhone)
myPhone := CameraPhone clone
myPhone click // --> "Taking snapshot"
myPhone call // --> "Calling home"</lang>
In Io each object has an internal list of prototype objects it inherits from. You can add to this list with appendProto.
Ioke
<lang ioke>Camera = Origin mimic MobilePhone = Origin mimic CameraPhone = Camera mimic mimic!(MobilePhone)</lang>
J
<lang j>coclass 'Camera'
create=: verb define
NB. creation-specifics for a camera go here
)
destroy=: codestroy
NB. additional camera methods go here
coclass 'MobilePhone'
create=: verb define
NB. creation-specifics for a mobile phone go here
)
destroy=: codestroy
NB. additional phone methods go here
coclass 'CameraPhone' coinsert 'Camera MobilePhone'
create=: verb define
create_Camera_ f. y create_MobilePhone_ f. y NB. creation details specific to a camera phone go here
)
destroy=: codestroy
NB. additional camera-phone methods go here</lang> The adverb Fix (f.) is needed as shown so the superclass constructors get executed in the object, not in the superclass.
Java
Java does not allow multiple inheritance, but you can "implement" multiple interfaces. All methods in interfaces are abstract (they don't have an implementation). When you implement an interface you need to implement the specified methods. <lang java>public interface Camera{
//functions here with no definition... //ex: //public void takePicture();
}</lang> <lang java>public interface MobilePhone{
//functions here with no definition... //ex: //public void makeCall();
}</lang> <lang java>public class CameraPhone implements Camera, MobilePhone{
//functions here...
}</lang>
Julia
Julia supports inheritance via abstract types. In Julia, multiple dispatch allows objects of different types to have the same function interfaces. Julia also can support traits via parameters in type declarations or with macros. This makes multiple inheritance in Julia mostly unnecessary, except for the inconvenience of composing the data in a mixed type when declaring multiple similar types, for which there are macros.
For example, the functions dialnumber(equipment, name) and video(equipment, filename) could be used as generic interfaces to implement methods for a Telephone, a Camera, and a SmartPhone, and Julia would dispatch according to the type of the equipment.<lang julia>
abstract type Phone end
struct DeskPhone <: Phone
book::Dict{String,String}
end
abstract type Camera end
struct kodak
roll::Vector{Array{Int32,2}}
end
struct CellPhone <: Phone
book::Dict{String,String}
roll::Vector{AbstractVector}
end
function dialnumber(phone::CellPhone)
println("beep beep")
end
function dialnumber(phone::Phone)
println("tat tat tat tat")
end
function snap(camera, img)
println("click")
push!(roll, img)
end
dphone = DeskPhone(Dict(["information" => "411"])) cphone = CellPhone(Dict(["emergency" => "911"]), [[]])
dialnumber(dphone) dialnumber(cphone)
</lang>
- Output:
tat tat tat tat beep beep
Kotlin
Interfaces in Kotlin are very similar to Java 8. They can contain declarations of abstract methods, as well as method implementations.
What makes them different from abstract classes is that interfaces cannot store state. They can have properties but these need
to be abstract or to provide accessor implementations.
<lang scala>interface Camera {
val numberOfLenses : Int
}
interface MobilePhone {
fun charge(n : Int) {
if (n >= 0)
battery_level = (battery_level + n).coerceAtMost(100)
}
var battery_level : Int
}
data class CameraPhone(override val numberOfLenses : Int = 1, override var battery_level: Int) : Camera, MobilePhone data class TwinLensCamera(override val numberOfLenses : Int = 2) : Camera
fun main(args: Array<String>) {
val c = CameraPhone(1, 50) println(c) c.charge(35) println(c) c.charge(78) println(c) println(listOf(c.javaClass.superclass) + c.javaClass.interfaces) val c2 = TwinLensCamera() println(c2) println(listOf(c2.javaClass.superclass) + c2.javaClass.interfaces)
}</lang>
- Output:
CameraPhone(numberOfLenses=1, battery_level=50) CameraPhone(numberOfLenses=1, battery_level=85) CameraPhone(numberOfLenses=1, battery_level=100) [class java.lang.Object, interface multiple_inheritance.Camera, interface multiple_inheritance.MobilePhone] TwinLensCamera(numberOfLenses=2) [class java.lang.Object, interface multiple_inheritance.Camera]
Lasso
Lasso only allow single inheritance. But it supports the use of multiple traits and trays hand down the methods it has implemented provided that the type fulfills the requirements for the trait. http://lassoguide.com/language/traits.html <lang Lasso>define trait_camera => trait { require zoomfactor
provide has_zoom() => { return .zoomfactor > 0 }
}
define trait_mobilephone => trait { require brand
provide is_smart() => { return .brand == 'Apple' }
}
define cameraphone => type {
trait { import trait_camera, trait_mobilephone }
data public zoomfactor::integer = 0, public brand::string
}
local(mydevice = cameraphone)
- mydevice -> brand = 'Apple'
- mydevice -> zoomfactor = 0
- mydevice -> has_zoom
'
'
- mydevice -> is_smart</lang>
-> false
true
Lingo
Lingo does not support multiple inheritance. But its slightly idiosyncratic inheritance implementation based on "ancestors" allows to assign/change inheritance relations at runtime. So a similar (but not identical) effect can be achieved by something like this: <lang lingo>-- parent script "Camera" property resolution
on new (me)
me.resolution = "1024x768" return me
end
on snap (me)
put "SNAP!"
end</lang>
<lang lingo>-- parent script "MobilePhone" property ringtone
on new (me)
me.ringtone = "Bell" return me
end
on ring (me, n)
repeat with i = 1 to n put "RING!!!" end repeat
end</lang>
<lang lingo>-- parent script "CameraPhone" property ancestor
on new (me)
c = script("Camera").new()
mp = script("MobilePhone").new()
-- make the Camera instance a parent of the MobilePhone instance mp.setProp(#ancestor, c)
-- make the MobilePhone instance a parent of this CameraPhone instance me.ancestor = mp
return me
end</lang>
Usage: <lang lingo>cp = script("CameraPhone").new()
cp.snap() -- "SNAP!"
cp.ring(3) -- "RING!!!" -- "RING!!!" -- "RING!!!"
put cp.resolution -- "1024x768"
put cp.ringtone -- "Bell"</lang>
Logtalk
Logtalk supports multiple inheritance. There is no "class" keyword in Logtalk; an "object" keyword is used instead (Logtalk objects play the role of classes, meta-classes, instances, or prototypes depending on the relations with other objects). <lang logtalk>:- object(camera,
...). ...
- - end_object.</lang>
<lang logtalk>:- object(mobile_phone,
...). ...
- - end_object.</lang>
<lang logtalk>:- object(camera_phone,
specializes(camera, mobile_phone), ...). ...
- - end_object.</lang>
Lua
Lua is prototype-based. A table cannot have more than one metatable, but it can reference more than one in its __index metamethod, by making it a closure.
<lang lua>function setmetatables(t,mts) --takes a table and a list of metatables
return setmetatable(t,{__index = function(self, k)
--collisions are resolved in this implementation by simply taking the first one that comes along.
for i, mt in ipairs(mts) do
local member = mt[k]
if member then return member end
end
end})
end
camera = {} mobilephone = {} cameraphone = setemetatables({},{camera,mobilephone})</lang>
M2000 Interpreter
<lang M2000 Interpreter> Module CheckIt {
Class Camera {
IamCamera
}
Class MobilePhone {
IamMobilePhone
}
Class CameraPhone {
Module CameraPhone {
\\ we can use : This=Camera() : This=MobilePhone()
\\ but we have to use Final for Functions/Modules in This
\\ So using M, a new local variable, we can accumulate Inheritance
M=Camera()
M=MobilePhone()
M=This
This=M
}
}
CP1=CameraPhone()
Print Valid(CP1.IamCamera)=True, Valid(CP1.IamMobilePhone)=true
} CheckIt </lang>
Nemerle
Like C#, Nemerle only allows pseudo-multiple inheritance through interfaces. In Nemerle, the base class must be listed before any interfaces. <lang nemerle>interface ICamera {
// ...
}
class MobilePhone {
// ...
}
class CameraPhone: MobilePhone, ICamera {
// ...
}</lang>
NetRexx
Like Java, NetRexx doesn't allow true multiple inheritance but instead restricts that capability to interfaces. NetRexx permits the implementation of multiple interfaces. All methods in interfaces are implicitly abstract, thus when you implement an interface you must implement its specified methods.
In this sample the class/interface names are augmented over those required in the task to prevent namespace pollution. The sample also provides a complete working implementation to demonstrate the capability. <lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols binary
class RInheritMultiple public
method main(args = String[]) public static
iPhone = RInheritMultiple_CameraPhone()
if iPhone <= RInheritMultiple_Camera then -
say -
'Object' hashToString(iPhone) '['iPhone.getClass().getSimpleName()']' -
'is a' RInheritMultiple_Camera.class.getSimpleName()
if iPhone <= RInheritMultiple_MobilePhone then -
say -
'Object' hashToString(iPhone) '['iPhone.getClass().getSimpleName()']' -
'is a' RInheritMultiple_MobilePhone.class.getSimpleName()
say iPhone.snap()
say iPhone.call()
return
method hashToString(that = Object) public static
return '@'(Rexx that.hashCode()).d2x().right(8, 0)
class RInheritMultiple_Camera private interface
-- properties follow... shutter = 'click...' -- method prototypes follow method snap() public returns Rexx
class RInheritMultiple_MobilePhone private interface
-- properties follow... ringTone = 'ring...' -- method prototypes follow method call() public returns Rexx
class RInheritMultiple_CameraPhone private -
implements - RInheritMultiple_Camera, - RInheritMultiple_MobilePhone - uses - RInheritMultiple_Camera, - RInheritMultiple_MobilePhone method RInheritMultiple_CameraPhone() public return -- method implementations follow method snap() public return shutter method call() public return ringTone</lang>
- Output:
Object @7F546C85 [RInheritMultiple_CameraPhone] is a RInheritMultiple_Camera Object @7F546C85 [RInheritMultiple_CameraPhone] is a RInheritMultiple_MobilePhone click... ring...
Objective-C
Like Java, Objective-C does not allow multiple inheritance, but a class can "conform to" multiple protocols. All methods in protocols are abstract (they don't have an implementation). When you conform to a protocol you need to implement the specified methods.
If you simply want to combine the functionality (method implementations) of multiple classes, you can use message forwarding to mimic the functionality of those classes without actually inheriting them, as described in this guide:
<lang objc>@interface Camera : NSObject { } @end
@implementation Camera @end
@interface MobilePhone : NSObject { } @end
@implementation MobilePhone @end
@interface CameraPhone : NSObject {
Camera *camera; MobilePhone *phone;
} @end
@implementation CameraPhone
-(instancetype)init {
if ((self = [super init])) {
camera = [[Camera alloc] init];
phone = [[MobilePhone alloc] init];
}
return self;
}
-(void)forwardInvocation:(NSInvocation *)anInvocation {
SEL aSelector = [anInvocation selector]; if ([camera respondsToSelector:aSelector]) [anInvocation invokeWithTarget:camera]; else if ([phone respondsToSelector:aSelector]) [anInvocation invokeWithTarget:phone]; else [self doesNotRecognizeSelector:aSelector];
}
-(NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
return [camera methodSignatureForSelector:aSelector] ?: [phone methodSignatureForSelector:aSelector] ?: [super methodSignatureForSelector:aSelector];
}
-(BOOL)respondsToSelector:(SEL)aSelector {
return [camera respondsToSelector:aSelector] || [phone respondsToSelector:aSelector] || [super respondsToSelector:aSelector];
}
@end</lang>
Caveat: the CameraPhone class will still technically not inherit from
either the Camera or MobilePhone classes, so testing a CameraPhone object with -isKindOfClass: with the Camera or MobilePhone classes will still fail.
OCaml
<lang ocaml>class camera =
object (self) (*functions go here...*) end</lang>
<lang ocaml>class mobile_phone =
object (self) (*functions go here...*) end</lang>
<lang ocaml>class camera_phone =
object (self) inherit camera inherit mobile_phone (*functions go here...*) end</lang>
Oforth
Oforth does not implement multiple inheritance. It allows only one parent class.
Oforth implements properties (like Comparable, Indexable, ...). A property can have attributes and methods. A class can have multiple properties.
If Camera and MobilePhone are designed as properties, we can write :
<lang Oforth>Property new: Camera Property new: MobilePhone
Object Class new: CameraPhone CameraPhone is: Camera CameraPhone is: MobilePhone</lang>
ooRexx
ooRexx classes have a single superclass and can inherit from multiple mixins. Mixins are more than just interfaces. They can contain concrete method implementations and also create instance variables (scoped as private variables to the mixin methods). <lang ooRexx> -- inherited classes must be created as mixinclasses.
- class phone mixinclass object
- class camera mixinclass object
-- not a direct subclass of either, but inherits both
- class cameraphone inherit phone camera
-- could also be
- class cameraphone1 subclass phone inherit camera
-- or
- class cameraphone2 subclass camera inherit phone</lang>
OxygenBasic
<lang oxygenbasic>class Camera
string cbuf method TakePhoto() end method method ViewPhoto() end method
end class
class MobilePhone
string pbuf method MakeCall() end method method TakeCall() end method
end class
class CameraPhone
has Camera,MobilePhone
end class
CameraPhone cp
cp.ViewPhoto cp.MakeCall</lang>
Oz
<lang oz>class Camera end
class MobilePhone end
class CameraPhone from Camera MobilePhone end</lang>
Pascal
See Delphi
Perl
<lang perl>package Camera;
- functions go here...
1;</lang>
<lang perl>package MobilePhone;
- functions go here...
1;</lang>
<lang perl>package CameraPhone; use Camera; use MobilePhone; @ISA = qw( Camera MobilePhone );
- functions go here...
1;</lang>
or
<lang perl>package CameraPhone; use base qw/Camera MobilePhone/;
- functions go here...</lang>
The same using the MooseX::Declare extention: <lang perl>use MooseX::Declare;
class Camera {
# methods ...
} class MobilePhone {
# methods ...
} class CameraPhone extends(Camera, MobilePhone) {
# methods ...
}</lang>
Perl 6
<lang perl6>class Camera {} class MobilePhone {} class CameraPhone is Camera is MobilePhone {}
say CameraPhone.^mro; # undefined type object say CameraPhone.new.^mro; # instantiated object</lang>
- Output:
CameraPhone() Camera() MobilePhone() Any() Mu() CameraPhone() Camera() MobilePhone() Any() Mu()
The .^mro is not an ordinary method call, but a call to the object's metaobject that returns the method resolution order for this type.
Phix
Needs 0.8.1+
inheritance
The programmer is expected to assume complete responsibility (away from the compiler) for checking/resolving any conflicts. <lang Phix> class Camra
string name = "nikkon"
end class class Mobile -- string name = "nokia" -- oops!
string mane = "nokia" -- ok!
end class class CamraPhone extends Camra,Mobile
procedure show() ?{name,mane} end procedure
end class CamraPhone cp = new() cp.show()</lang>
- Output:
{"nikkon","nokia"}
composition
The programmer is expected to assume complete responsibility for invoking new() appropriately.
The example below shows four different approaches to invoking all the new() that are needed (one pair commented out).
Note that invoking new() inside a class definition creates shared references to a single instance.
The compiler demands to be explicitly told what the inner/inlined new() on cp2 are actually for.
<lang Phix>class Camera
public string name = "nikkon"
end class class MobilePhone
public string name = "nokia" -- (clash no more)
end class class CameraPhone -- Camera c = new() -- MobilePhone m = new()
public Camera c
public MobilePhone m
procedure show() ?{c.name,m.name} end procedure
end class Camera c = new({"canon"}) MobilePhone m = new() CameraPhone cp1 = new({c,m}),
cp2 = new({new("Camera"),new("MobilePhone")}),
cp3 = new() -- (internal/shared/NULL c,m)
cp3.c = new() -- (obviously c must be public) cp3.m = new({"LG20"}) -- "" m "" "" cp1.show() cp2.show() cp3.show() -- crashes without internal/above new()</lang>
- Output:
{"canon","nokia"}
{"nikkon","nokia"}
{"nikkon","LG20"}
PicoLisp
<lang PicoLisp>(class +Camera)
(class +MobilePhone)</lang>
Pop11
<lang pop11>;;; load object support lib objectclass;
define :class Camera;
;;; slots go here
enddefine;
define :class MobilePhone;
;;; slots go here
enddefine;
define :class CameraPhone is Camera, MobilePhone;
;;; extra slots go here
enddefine;
- methods go here</lang>
PowerShell
<lang PowerShell> class Camera {} class MobilePhone {} class CameraPhone : Camera, MobilePhone {} </lang>
PureBasic
Using the open-source precompiler SimpleOOP. <lang PureBasic>Class Camera EndClass
Class Mobil EndClass
Class CameraMobile Extends Camera Extends Mobil EndClass</lang>
Python
<lang python>class Camera:
pass #functions go here...</lang>
<lang python>class MobilePhone:
pass #functions go here...</lang>
<lang python>class CameraPhone(Camera, MobilePhone):
pass #functions go here...</lang>
Racket
Racket allows multiple inheritance with interfaces, but not classes. Mixins can be used to achieve some of the benefits of multiple inheritance.
<lang racket>#lang racket
(define camera<%> (interface ())) (define mobile-phone<%> (interface ()))
(define camera-phone%
(class* object% (camera<%> mobile-phone<%>) (super-new) ;; implement methods here ))</lang>
Ring
<lang ring>
- Project : Inheritance/Multiple
mergemethods(:CameraPhone,:MobilePhone)
o1 = new CameraPhone ? o1 ? o1.testCamera() ? o1.testMobilePhone()
func AddParentClassAttributes oObject,cClass
# Add Attributes
cCode = "oTempObject = new " + cClass
eval(cCode)
for cAttribute in Attributes(oTempObject)
AddAttribute(oObject,cAttribute)
cCode = "oObject." + cAttribute + " = oTempObject." + cAttribute
eval(cCode)
next
class Camera
Name = "Camera"
func testCamera
? "Message from testCamera"
class MobilePhone
Type = "Android"
func testMobilePhone
? "Message from MobilePhone"
class CameraPhone from Camera
# Add MobilePhone Attributes
AddParentClassAttributes(self,:MobilePhone)
</lang> Output:
name: Camera type: Android Message from testCamera Message from MobilePhone
Ruby
Ruby does not have multiple inheritance, but you can mix modules into classes: <lang ruby>module Camera
# define methods here
end class MobilePhone
# define methods here
end class CameraPhone < MobilePhone
include Camera # define methods here
end</lang>
Rust
<lang Rust>trait Camera {} trait MobilePhone {} trait CameraPhone: Camera + MobilePhone {}</lang>
Scala
<lang scala>trait Camera trait MobilePhone class CameraPhone extends Camera with MobilePhone</lang>
Self
Self is a class-free, object-oriented language, and as such, it uses prototypal inheritance instead of classical inheritance. This is an example of the relevant excerpts from a Self transporter fileout. Normally the object tree would be built and navigated within the graphical Self environment. <lang self>camera = ()</lang> <lang self>mobilePhone = ()</lang> <lang self>cameraPhone = (| cameraParent* = camera. mobilePhoneParent* = mobilePhone |)</lang>
Sidef
<lang ruby>class Camera {}; class MobilePhone {}; class CameraPhone << Camera, MobilePhone {};</lang>
Slate
<lang slate>define: #Camera. define: #MobilePhone. define: #CameraPhone &parents: {Camera. MobilePhone}.</lang>
Swift
Like Objective-C, Swift does not allow multiple inheritance. However, you can conform to multiple protocols. <lang Swift>protocol Camera {
}
protocol Phone {
}
class CameraPhone: Camera, Phone {
}</lang>
Tcl
or
<lang tcl>package require TclOO
oo::class create Camera oo::class create MobilePhone oo::class create CameraPhone {
superclass Camera MobilePhone
}</lang>
zkl
<lang zkl>class Camera{} class MobilePhone{} class CameraPhone(Camera,MobilePhone){} CameraPhone.linearizeParents</lang>
- Output:
Show the class search order
L(Class(CameraPhone),Class(Camera),Class(MobilePhone))
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