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This comparison of programming languages compares how object-oriented programming languages such as C++, Java, Smalltalk, Object Pascal, Perl, Python, and others manipulate data structures.
construction | destruction | |
---|---|---|
ABAP Objects | data variable type ref to class . [1] | [2] [3] |
APL (Dyalog) | variable←⎕NEW class «parameters» | ⎕EX 'variable' |
C++ | class variable«(parameters)»; [4] orclass * variable = new class«(parameters)»; [5] | delete pointer; |
C# | class variable = new class(parameters); | variable.Dispose(); [3] |
Java | [3] | |
D | destroy(variable); | |
eC | class «instance handle» { «properties/data members assignments, instance method overrides» } | delete instance handle; |
Objective-C (Cocoa) | class * variable = [[class alloc ] init]; or class * variable = [[class alloc ] initWithFoo:parameter «bar:parameter ...»]; | [variable release]; |
Swift | let variable = class(parameters) | |
Python | variable = class(parameters) | del variable [3] (Normally not needed) |
Visual Basic .NET | Dim variable As New class(parameters) | variable.Dispose() [3] |
Xojo | Dim variable As New class(parameters) | variable = Nil |
Eiffel | create variable orcreate «{TYPE}» variable.make_foo «(parameters)» orvariable := create{TYPE} orvariable := create {TYPE}.make_foo «(parameters)» | [3] |
PHP | $ variable = new class«(parameters)»; | unset($variable); [3] |
Perl 5 | «my »$variable = class->new«(parameters)»; | undef($variable); |
Raku | «my »$variable = class.new«(parameters)»; | $variable.undefine; |
Ruby | variable = class.new«(parameters)» | [3] |
Windows PowerShell | $variable = New-Object «-TypeName» class ««-ArgumentList» parameters» | Remove-Variable «-Name» variable |
OCaml | let variable = new class «parameters» or let variable = object members end [6] | [3] |
F# | let variable = «new »class(«parameters») | |
Smalltalk | The class is an Object. Just send a message to a class, usually #new or #new: , and many others, for example: Pointx:10y:20.Arraywith:-1with:3with:2. | |
JavaScript | var variable = new class«(parameters)» or var variable = { «key1: value1«, key2: value2 ...»»} | [3] |
Object Pascal (Delphi) | ClassVar := ClassType.ConstructorName(parameters); | ClassVar.Free; |
Scala | valobj=newObject// no parametersvalobj=newObject(arg0,arg1,arg2...)valobj=Object(arg0,arg1,arg2...)// case classvalobj=newObject(arg0,arg1,param1=value1,...)// named parameters | [3] |
COBOL | INVOKE class "NEW"RETURNING variable orMOVE class::"NEW"TO variable | |
Cobra | variable «as class» = class(parameters) | variable.dispose |
ISLISP | (setq variable (create (class <some-class> [:field-1 value-1 [:field-2 value-2] ..]))) | [3] |
class | protocol | namespace | |
---|---|---|---|
ABAP Objects | class name definition «inheriting from parentclass». «interfaces: interfaces.» method_and_field_declarations endclass. | interface name. members endinterface. | — |
APL (Dyalog) | :Class name «:parentclass» «,interfaces» members :EndClass | :Interface name members :EndInterface | :Namespace name members :EndNamespace |
C++ | class name« : public parentclasses [7] » { members }; | namespace name { members } | |
C# | class name« : «parentclass»«, interfaces»» { members } | interface name« : parentinterfaces» { members } | |
D | module name; | ||
eC | class name« : base class» { «default member values assignments» «members» } |
| namespace name; |
Java | class name« extends parentclass»« implements interfaces» { members } | interface name« extends parentinterfaces» { members } | package name; members |
PHP | namespace name; members | ||
Objective-C | @interface name« : parentclass» [8] «< protocols >» { instance_fields } method_and_property_declarations @end [9] | @protocol name«< parentprotocols >» members @end | [10] |
Swift | class name« : «parentclass»«, protocols»» { members } | protocol name« : parentprotocols» { members } | |
Python | class name«(parentclasses [7] )»: | [11] | __all__ = [ member1,member2,... ] |
Visual Basic .NET | Class name« Inherits parentclass»« Implements interfaces» | Interface name« Inherits parentinterfaces» | Namespace name |
Xojo | Class name« Inherits parentclass»« Implements interfaces» | Interface name« Inherits parentinterfaces» | Module name |
Eiffel | class name« inherit parentclasses [7] » | — | |
Perl | package name; «@ISA = qw(parentclasses [7] );» members 1; | package name; members | |
Raku | class name «is parentclass «is parentclass ... [7] »» «does role «does role ...»» { members } | role name «does role «does role ...»» { members } | module name { members } |
Ruby | class name« < parentclass» | module name | |
Windows PowerShell | — | ||
OCaml | class name «parameters» = object «(self)» «inherit parentclass «parameters» «inherit parentclass «parameters» ... [7] »» members end | module name | |
F# | type name«(parameters)»«as this» = class «inherit parentclass«(parameters)» «as base»» members «interface interface with implementation «interface interface with implementation ...»» end | type name = interface members end | namespace name |
Smalltalk | [12] | [13] | |
JavaScript (ES6) | class name «extends parentclass» { members } | ||
Object Pascal (Delphi) | ClassName = Class «(ClassParent, Interfaces)» | package name; members | |
Scala | classConcreteClass(constructorparams)extendsParentClasswithTrait1withTrait2withTrait2{// members} | traitTraitNameextendsOtherTrait1withOtherTrait2withOtherTrait3{// members} | packagename |
COBOL | CLASS-ID. name« INHERITS« FROM» parentclasses». FACTORY« IMPLEMENTS interfaces». class-members END FACTORY. OBJECT« IMPLEMENTS interfaces». instance-members END OBJECT.
| INTERFACE-ID. name« INHERITS« FROM» interfaces». members
| — |
Cobra | class name «inherits parentclass» «implements interfaces» | interface name «inherits parentinterfaces» | namespace name |
ISLISP | (defclass name (base-class) ((x :initform 0 :accessor get-x :initarg x)) (:abstractp nil)) |
constructor | destructor | finalizer [14] | |
---|---|---|---|
ABAP Objects | methods constructor «importing parameter = argument» [15] | — | |
APL (Dyalog) | ∇ name :Implements Constructor «:Base «expr»» instructions ∇ | ∇ name :Implements Destructor instructions ∇ | |
C++ | class(«parameters») «: initializers [16] » { instructions } | ~class() { instructions } | |
C# | class(«parameters») { instructions } | void Dispose(){ instructions } | ~class() { instructions } |
D | this(«parameters») { instructions } | ~this() { instructions } | |
eC | class() { instructions } | ~class() { instructions } | |
Java | class(«parameters») { instructions } | void finalize() { instructions } | |
Eiffel | [17] | [18] | |
Objective-C (Cocoa) |
|
|
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Swift | init(«parameters») { instructions } | deinit { instructions } | |
Python |
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| |
Visual Basic .NET |
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|
|
Xojo | Sub Constructor(«parameters») | Sub Destructor() | |
PHP |
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| |
Perl |
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| |
Raku |
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| |
Ruby | def initialize«(parameters)» | — | |
Windows PowerShell | — | ||
OCaml | initializer instructions [19] | — | |
F# | do instructions or [20] |
|
|
JavaScript | function name(«parameters»){ instructions } [21] | — | |
JavaScript (ES6) | constructor( «parameters») { instructions } | ||
COBOL | — [22] | — | |
Cobra | cue init(parameters) | def dispose | |
ISLISP | (defmethod initialize-object ((instance <class-name>) initvalues) |
public | private | protected | friend | |
---|---|---|---|---|
ABAP Objects | public section. [23] data field type type. | private section. [23] data field type type. | protected section. [23] data field type type. | [24] |
APL (Dyalog) | :Field Public field «← value» | :Field «Private» field «← value» | ||
C++ | public: type field; | private: type field; | protected: type field; | [25] |
C# | public type field «= value»; | private type field «= value»; | protected type field «= value»; | internal type field «= value»; |
D | package type field «= value»; | |||
Java | protected type field «= value»; | type field «= value»; | ||
eC | public type field; | private type field; | ||
Eiffel | feature | feature {NONE} | feature {current_class} | feature {FRIEND} |
Objective-C | @public type field; | @private type field; | @protected type field; | @package type field; |
Swift | — | |||
Smalltalk | — | [26] | — | |
Python | self.field = value [27] | — [28] | — | |
Visual Basic .NET | Public field As type «= value» | Private field As type «= value» | Protected field As type «= value» | Friend field As type «= value» |
Xojo | Public field As type «= value» | Private field As type «= value» | Protected field As type «= value» | — |
PHP | public $field «= value»; | private $field «= value»; | protected $field «= value»; | |
Perl | $self->{field} = value; [27] | — | ||
Raku | has« type »$.field« is rw» | has« type »$!field | — | |
Ruby | — | @ field = value [27] | ||
Windows PowerShell | Add-Member | — | ||
OCaml | — | val «mutable» field = value | — | |
F# | — | let «mutable» field = value | — | |
JavaScript | this.field = value [27] | |||
COBOL | — | level-number field clauses. [29] | — | — |
Cobra | var field «as type» «= value» | var__field «as type» «= value» | var_field «as type» «= value» | |
ISLISP | (field :initform value :accessor accessor-name :initarg keyword) |
basic/void method | value-returning method | ||
---|---|---|---|
ABAP Objects | methods name «importing parameter = argument» «exporting parameter = argument» «changing parameter = argument» «returning value(parameter)» [30] | [31] | |
APL (Dyalog) | ∇ «left argument» name «right arguments» instructions ∇ | ∇ result ← «left argument» name «right arguments» instructions ∇ | |
C++ [32]
The implementation of methods is usually provided in a separate source file, with the following syntax
| void foo(«parameters») { instructions } | type foo(«parameters») { instructions ... return value; } | |
C# | |||
D | |||
Java | |||
eC | void ««type of 'this'»::»foo(«parameters») { instructions } | type ««type of this»::»foo(«parameters») { instructions ... return value; } | |
Eiffel | foo ( «parameters» ) | foo ( «parameters» ): TYPE | |
Objective-C | - (void)foo«:parameter «bar:parameter ...»» { instructions } | - (type)foo«:parameter «bar:parameter ...»» { instructions... return value; } | |
Swift | func foo(«parameters») { instructions } | func foo(«parameters») -> type { instructions... return value } | |
Python | def foo(self«, parameters»): | def foo(self«, parameters»): | |
Visual Basic .NET | Sub Foo(«parameters») | Function Foo(«parameters») As type | |
Xojo | Sub Foo(«parameters») | Function Foo(«parameters») As type | |
PHP | function foo(«parameters»)«: void» { instructions } | function foo(«parameters»)«: type» { instructions ... return value; } | |
Perl | sub foo { my ($self«, parameters») = @_; instructions } | sub foo { my ($self«, parameters») = @_; instructions ... return value; } | |
Raku | «has »«multi »method foo(««$self: »parameters») { instructions } | «has «type »»«multi »method foo(««$self: »parameters») { instructions ... return value; } | |
Ruby | def foo«(parameters)» | def foo«(parameters)» | |
Windows PowerShell | Add-Member «-MemberType» ScriptMethod «-Name» foo «-Value» { «param(parameters)»instructions } -InputObject variable | Add-Member «-MemberType» ScriptMethod «-Name» foo «-Value» { «param(parameters)»instructions ... return value } -InputObject variable | |
OCaml | — | method foo «parameters» = expression | |
F# | member this.foo(«parameters») = expression | ||
JavaScript | this.method = function(«parameters») {instructions} [34] | this.method = function(«parameters») {instructions... return value;} [34] | |
Javascript (ES6) | foo(«parameters») {instructions} | foo(«parameters») {instructions... return value;} | |
COBOL | METHOD-ID. foo. instructions
| METHOD-ID. foo. instructions
| |
Cobra | def foo(parameters) | def foo(parameters) as type | |
ISLISP | (defgeneric method (arg1 arg2)) |
How to declare a property named "Bar"
read-write | read-only | write-only | |
---|---|---|---|
ABAP Objects | — | ||
APL (Dyalog) | :Property Bar ∇ result ← Get instructions ∇ ∇ Set arguments instructions ∇ :EndProperty Bar | :Property Bar ∇ result ← Get instructions ∇ :EndProperty Bar | :Property Bar ∇ Set arguments instructions ∇ :EndProperty Bar |
C++ | — | ||
C# | type Bar { | type Bar { get { instructions ... return value;} } | type Bar { set { instructions } } |
D | @property type bar() { instructions ... return value;} | @property type bar() { instructions ... return value;} | @property type bar(type value) { instructions ... return value;} |
eC | property type Bar { | property type Bar { get { instructions ... return value;} } | property type Bar { set { instructions } } |
Java | — | ||
Objective-C 2.0 (Cocoa) | @property (readwrite) type bar; and then inside @implementation | @property (readonly) type bar; and then inside @implementation | — |
Swift | var bar : type { get { instructions } set«(newBar)» { instructions } } | var bar : type { instructions } | — |
Eiffel | feature -- Access | ||
Python | def setBar(self, value): [35] | def getBar(self): | def setBar(self, value): |
Visual Basic .NET | Property Bar() As type | ReadOnly Property Bar() As type | WriteOnly Property Bar() As type |
Xojo | ComputedProperty Bar() As type | ComputedProperty Bar() As type | ComputedProperty Bar() As type |
PHP | function __get($property) { | function __get($property) { | function __set($property, $value) { |
Perl | sub Bar { | sub Bar { | sub Bar { |
Raku | — | ||
Ruby | def bar | def bar | def bar=(value) |
Windows PowerShell | Add-Member | Add-Member | Add-Member |
OCaml | — | ||
F# | member this.Bar with get() = expression and set(value) = expression | member this.Bar = expression | member this.Bar with set(value) = expression |
JavaScript (ES6) | get bar(«parameters»){ instructions ... return value}set bar(«parameters») { instructions } | get bar(«parameters»){ instructions ... return value} | set bar(«parameters») { instructions } |
COBOL | METHOD-ID. GET PROPERTY bar. instructions
instructions
| METHOD-ID. GET PROPERTY bar. instructions
| METHOD-ID. SET PROPERTY bar. instructions
|
Cobra | pro bar «as type» | get bar «as type» | set bar «as type» |
ISLISP | — |
read-write | read-only | write-only | |
---|---|---|---|
ABAP Objects | — | ||
C++ | — | ||
C# | type Bar { get; set; } | type Bar { get; private set; } | type Bar { private get; set; } |
D | — | ||
Java | — | ||
Objective-C 2.0 (Cocoa) | @property (readwrite) type bar; and then inside @implementation | @property (readonly) type bar; and then inside @implementation | — |
Swift | var bar : type | let bar : type | — |
Eiffel | |||
Python | @property | @property | bar = property() |
Visual Basic .NET | Property Bar As type« = initial_value» (VB 10) | ||
PHP | |||
Perl [36] | usebaseqw(Class::Accessor); | usebaseqw(Class::Accessor); | usebaseqw(Class::Accessor); |
Raku | — | ||
Ruby | attr_accessor :bar | attr_reader :bar | attr_writer :bar |
Windows PowerShell | |||
OCaml | — | ||
F# | member val Bar = value with get, set | ||
COBOL | level-number bar clauses PROPERTY. | level-number bar clauses PROPERTY «WITH» NO SET. | level-number bar clauses PROPERTY «WITH» NO GET. |
Cobra | pro bar from var «as type» | get bar from var «as type» | set bar from var «as type» |
unary | binary | function call | |
---|---|---|---|
ABAP Objects | — | ||
C++ | type operator symbol () { instructions } | type operator symbol (type operand2) { instructions } | type operator () («parameters») { instructions } |
C# | static type operator symbol(type operand) { instructions } | static type operator symbol(type operand1, type operand2) { instructions } | — |
D | type opUnary(string s)() if (s == "symbol") { instructions } | type opBinary(string s)(type operand2) if (s == "symbol") { instructions } | type opCall(«parameters») { instructions } |
Java | — | ||
Objective-C | |||
Swift | func symbol(operand1 : type) -> returntype { instructions } (outside class) | func symbol(operand1 : type1, operand2 : type2) -> returntype { instructions } (outside class) | |
Eiffel [37] | op_name alias "symbol": TYPE | op_name alias "symbol" (operand: TYPE1): TYPE2 | |
Python | def __opname__(self): | def __opname__(self, operand2): | def __call__(self«, parameters»): |
Visual Basic .NET | Shared Operator symbol(operand As type) As type | Shared Operator symbol(operand1 As type, operand2 As type) As type | — |
Xojo | Function Operator_name(operand As type) As type | — | |
PHP | [38] | function __invoke(«parameters») { instructions } (PHP 5.3+) | |
Perl | use overload "symbol" => sub { my ($self) = @_; instructions }; | use overload "symbol" => sub { my ($self, $operand2, $operands_reversed) = @_; instructions }; | |
Raku | «our «type »»«multi »method prefix:<symbol> («$operand: ») { instructions ... return value;} or | «our «type »»«multi »method infix:<symbol> («$operand1: » type operand2) { instructions ... return value;} | «our «type »»«multi »method postcircumfix:<( )> («$self: » «parameters») { instructions } |
Ruby | def symbol | def symbol(operand2) | — |
Windows PowerShell | — | ||
OCaml | |||
F# | static member (symbol) operand = expression | static member (symbol)(operand1, operand2) = expression | — |
COBOL | — | ||
ISLISP | — | ||
read-write | read-only | write-only | |
---|---|---|---|
ABAP Objects | — | ||
APL (Dyalog) | :Property Numbered Default name ∇ result ← Get instructions ∇ ∇ Set arguments instructions ∇ :EndProperty Bar | :Property Numbered Default Bar ∇ result ← Get instructions ∇ :EndProperty Bar | :Property Numbered Default Bar ∇ Set arguments instructions ∇ :EndProperty Bar |
C++ | type& operator[](type index) { instructions } | type operator[](type index) { instructions } | |
C# | type this[type index] { | type this[type index] { get{ instructions } } | type this[type index] { set{ instructions } } |
D | type opIndex(type index) { instructions } | type opIndex(type index) { instructions } | type opIndexAssign(type value, type index) { instructions } |
Java | — | ||
Objective-C (recent Clang compiler) | — | - (id)objectAtIndexedSubscript:(NSUInteger)index { instructions return value; } or | - (void)setObject:(id)value atIndexedSubscript:(NSUInteger)index { instructions } or |
Swift | subscript (index : type) -> returntype { get { instructions } set«(newIndex)» { instructions } } | subscript (index : type) -> returntype { instructions } | |
Eiffel [37] | bracket_name alias "[]" (index: TYPE): TYPE assign set_item | bracket_name alias "[]" (index: TYPE): TYPE | |
Python | def __getitem__(self, index): | def __getitem__(self, index): | def __setitem__(self, index, value): |
Visual Basic .NET | Default Property Item(Index As type) As type | Default ReadOnly Property Item(Index As type) As type | Default WriteOnly Property Item(Index As type) As type |
PHP | [39] | ||
Perl | [40] | ||
Raku | «our «type »»«multi »method postcircumfix:<[ ]> is rw («$self: » type $index) { instructions ... return value;} or | «our «type »»«multi »method postcircumfix:<[ ]>(«$self: » type $index) { instructions ... return value;} or | — |
Ruby | def [](index) | def [](index) | def []=(index, value) |
Windows PowerShell | — | ||
OCaml | |||
F# | member this.Item with get(index) = expression and set index value = expression | member this.Item with get(index) = expression | member this.Item with set index value = expression |
COBOL | — | ||
Cobra | pro[index «as type»] as type | get[index «as type»] as type | set[index «as type»] as type |
downcast | upcast | |
---|---|---|
ABAP Objects | — | |
C++ | operator returntype() { instructions } | |
C# | static explicit operator returntype(type operand) { instructions } | static implicit operator returntype(type operand) { instructions } |
D | T opCast(T)() if (is(T == type)) { instructions } | |
eC | property T { get { return «conversion code»; } } | |
Java | — | |
Objective-C | ||
Eiffel [37] | ||
Python | ||
Visual Basic .NET | Shared Narrowing Operator CType(operand As type) As returntype | Shared Widening Operator CType(operand As type) As returntype |
PHP | — | |
Perl | ||
Raku | multi method type«($self:)» is export { instructions } | |
Ruby | — | |
Windows PowerShell | ||
OCaml | ||
F# | ||
COBOL | — | |
How to access members of an object x
object member | class member | namespace member | |||
---|---|---|---|---|---|
method | field | property | |||
ABAP Objects | x->method(«parameters»). [41] | x->field | — | x=>field or x=>method(«parameters [41] »). | — |
C++ | x.method(parameters) or | x.field or | cls::member | ns::member | |
Objective-C | [x method«:parameter «bar:parameter ...»»] | x->field | x.property (2.0 only) or | [cls method«:parameter «bar:parameter ...»»] | |
Smalltalk | x method«:parameter «bar:parameter ...»» | — | cls method«:parameter «bar:parameter ...»» | ||
Swift | x.method(parameters) | x.property | cls.member | ||
APL (Dyalog) | left argument» x.method «right argument(s)» | x.field | x.property | cls.member | ns.member |
C# | x.method(parameters) | ||||
Java | — | ||||
D | x.property | ||||
Python | |||||
Visual Basic .NET | |||||
Xojo | |||||
Windows PowerShell | [cls]::member | ||||
F# | — | cls.member | |||
eC | x.method«(parameters)» | x.field | x.property | cls::member | ns::member |
Eiffel | x.method«(parameters)» | x.field | {cls}.member | — | |
Ruby | — | x.property | cls.member | ||
PHP | x->method(parameters) | x->field | x->property | cls::member | ns\member |
Perl | x->method«(parameters)» | x->{field} | cls->method«(parameters)» | ns::member | |
Raku | x.method«(parameters)» or | x.field or | cls.method«(parameters)» or | ns::member | |
OCaml | x#method «parameters» | — | |||
JavaScript | x.method(parameters) | x.field | x.property | cls.member | — |
COBOL | INVOKE x"method" «USING parameters» «RETURNING result» or | — | property OF x | INVOKE cls "method" «USING parameters» «RETURNING result» or | — |
Cobra | x.method«(parameters)» | x.field | x.property | cls.member | ns.member |
Has member? | Handler for missing member | |||
---|---|---|---|---|
Method | Field | Method | Field | |
APL (Dyalog) | 3=x.⎕NC'method' | 2=x.⎕NC'method' | — | |
ABAP Objects | — | |||
C++ | ||||
Objective-C (Cocoa) | [x respondsToSelector:@selector(method)] | — | forwardInvocation: | — |
Smalltalk | x respondsTo: selector | — | doesNotUnderstand: | — |
C# | (using reflection) | |||
eC | ||||
Java | ||||
D | opDispatch() | |||
Eiffel | — | |||
Python | hasattr(x, "method") and callable(x.method) | hasattr(x, "field") | __getattr__() | |
Visual Basic .NET | (using reflection) | |||
Xojo | (using Introspection) | |||
Windows PowerShell | (using reflection) | |||
F# | (using reflection) | |||
Ruby | x.respond_to?(:method) | — | method_missing() | — |
PHP | method_exists(x, "method") | property_exists(x, "field") | __call() | __get() / __set() |
Perl | x->can("method") | exists x->{field} | AUTOLOAD | |
Raku | x.can("method") | x.field.defined | AUTOLOAD | |
OCaml | — | |||
JavaScript | typeof x.method === "function" | field in x | ||
COBOL | — |
current object | current object's parent object | null reference | Current Context of Execution | |
---|---|---|---|---|
Smalltalk | self | super | nil | thisContext |
ABAP Objects | me | super | initial | |
APL (Dyalog) | ⎕THIS | ⎕BASE | ⎕NULL | |
C++ | *this | [42] | NULL, nullptr | |
C# | this | base [43] | null | |
Java | super [43] | |||
D | ||||
JavaScript | super [43] (ECMAScript 6) | null, undefined [44] | ||
eC | this | null | ||
Objective-C | self | super [43] | nil | |
Swift | self | super [43] | nil [45] | |
Python | self [46] | super(current_class_name, self) [7] super() (3.x only) | None | |
Visual Basic .NET | Me | MyBase | Nothing | |
Xojo | Me / Self | Parent | Nil | |
Eiffel | Current | Precursor «{superclass}» «(args)» [43] [47] | Void | |
PHP | $this | parent [43] | null | |
Perl | $self [46] | $self->SUPER [43] | undef | |
Raku | self | SUPER | Nil | |
Ruby | self | super«(args)» [48] | nil | binding |
Windows PowerShell | $this | $NULL | ||
OCaml | self [49] | super [50] | — [51] | |
F# | this | base [43] | null | |
COBOL | SELF | SUPER | NULL | |
Cobra | this | base | nil |
String representation | Object copy | Value equality | Object comparison | Hash code | Object ID | ||
---|---|---|---|---|---|---|---|
Human-readable | Source-compatible | ||||||
ABAP Objects | — | ||||||
APL (Dyalog) | ⍕x | ⎕SRC x | ⎕NS x | x = y | — | ||
C++ | x == y [52] | pointer to object can be converted into an integer ID | |||||
C# | x.ToString() | x.Clone() | x.Equals(y) | x.CompareTo(y) | x.GetHashCode() | System | |
Java | x.toString() | x.clone() [53] | x.equals(y) | x.compareTo(y) [54] | x.hashCode() | System | |
JavaScript | x.toString() | ||||||
D | x.toString() or | x.stringof | x == y or | x.opCmp(y) | x.toHash() | ||
eC | x.OnGetString(tempString, null, null) or | y.OnCopy(x) | x.OnCompare(y) | object handle can be converted into an integer ID | |||
Objective-C (Cocoa) | x.description | x.debugDescription | [x copy] [55] | [x isEqual:y] | [x compare:y] [56] | x.hash | pointer to object can be converted into an integer ID |
Swift | x.description [57] | x.debugDescription [58] | x == y [59] | x < y [60] | x.hashValue [61] | reflect(x) | |
Smalltalk | x displayString | x printString | x copy | x = y | x hash | x identityHash | |
Python | str(x) [62] | repr(x) [63] | copy.copy(x) [64] | x == y [65] | cmp(x, y) [66] | hash(x) [67] | id(x) |
Visual Basic .NET | x.ToString() | x.Clone() | x.Equals(y) | x.CompareTo(y) | x.GetHashCode() | ||
Eiffel | x.out | x.twin | x.is_equal(y) | When x is COMPARABLE , one can simply do x < y | When x is HASHABLE , one can use x.hash_code | When x is IDENTIFIED , one can use x.object_id | |
PHP | $x->__toString() | clone x [68] | x == y |
| spl_object_hash(x) | ||
Perl | "$x" [69] | Data::Dumper [70] | Storable [71] | Scalar [72] | |||
Raku | ~x [69] | x.perl | x.clone | x eqv y | x cmp y | x.WHICH | |
Ruby | x.to_s | x.inspect | x.dup or | x == y or | x <=> y | x.hash | x.object_id |
Windows PowerShell | x.ToString() | x.Clone() | x.Equals(y) | x.CompareTo(y) | x.GetHashCode() | ||
OCaml | Oo.copy x | x = y | Hashtbl | Oo.id x | |||
F# | string x or x | sprintf "%A" x | x.Clone() | x = y or x | compare x y or x | hash x or x | |
COBOL | — |
Get object type | Is instance of (includes subtypes) | Upcasting | Downcasting | ||
---|---|---|---|---|---|
Runtime check | No check | ||||
ABAP Objects | — [73] | = | ?= | ||
C++ | typeid(x) | dynamic_cast<type *>(&x) != nullptr | — [74] | dynamic_cast<type*>(ptr) | (type*) ptr or |
C# | x.GetType() | x is type | (type) x or x as type | ||
D | typeid(x) | cast(type) x | |||
Delphi | x is type | x as type | |||
eC | x._class | eClass_IsDerived(x._class, type) | (type) x | ||
Java | x.getClass() | x instanceof class | (type) x | ||
Objective-C (Cocoa) | [x class] [75] | [x isKindOfClass:[class class]] | (type*) x | ||
Swift | x.dynamicType | x is type | x as! type x as? type | ||
JavaScript | x.constructor(If not rewritten.) | x instanceof class | — [76] | ||
Visual Basic .NET | x.GetType() | TypeOf x Is type | — [74] | CType(x, type) or TryCast(x, type) | |
Xojo | Introspection.GetType(x) | x IsA type | — | CType(x, type) | — |
Eiffel | x.generating_type | attached {TYPE} x | attached {TYPE} x as down_x | ||
Python | type(x) | isinstance(x, type) | — [76] | ||
PHP | get_class(x) | x instanceof class | |||
Perl | ref(x) | x->isa("class") | |||
Raku | x.WHAT | x.isa(class) | — [74] | type(x) or | |
Ruby | x.class | x.instance_of?(type) or | — [76] | ||
Smalltalk | x class | x isKindOf: class | |||
Windows PowerShell | x.GetType() | x -is [type] | — [74] | [type]x or x -as [type] | |
OCaml | — [77] | (x :> type) | — | ||
F# | x.GetType() | x :? type | (x :?> type) | ||
COBOL | — | x AS type [74] | — | ||
Import namespace | Import item | ||
---|---|---|---|
qualified | unqualified | ||
ABAP Objects | |||
C++ | using namespace ns; | using ns::item ; | |
C# | using ns; | using item = ns.item; | |
D | import ns; | import ns : item; | |
Java | import ns.*; | import ns.item; | |
Objective-C | |||
Visual Basic .NET | Imports ns | ||
Eiffel | |||
Python | import ns | from ns import * | from ns import item |
PHP | use ns; | use ns\item; | |
Perl | use ns; | use ns qw(item); | |
Raku | |||
Ruby | |||
Windows PowerShell | |||
OCaml | open ns | ||
F# | |||
COBOL | — |
Precondition | Postcondition | Check | Invariant | Loop | |
---|---|---|---|---|---|
ABAP Objects | — | ||||
C++ | |||||
C# | Spec#: | Spec#: | |||
Java | — | ||||
Objective-C | |||||
Visual Basic .NET | |||||
D | f | f | assert(expression) | invariant() { expression } | |
Eiffel | f | f | f | class X | from instructions |
Python | — | ||||
PHP | |||||
Perl | |||||
Raku | PRE { condition } | POST { condition } | |||
Ruby | — | ||||
Windows PowerShell | |||||
OCaml | |||||
F# | |||||
COBOL |
NSObject
for Cocoa and GNUstep, or Object
otherwise.@interface
portion is placed into a header file, and the @interface
portion is placed into a separate source code file."member_name(parameters)"
"class_name(parameters)".
classaddInstVarName:field.classremoveInstVarName:field.
defbar():doc="The bar property."deffget(self):returnself._bardeffset(self,value):self._bar=valuereturnlocals()bar=property(**bar())
x->method(«exporting parameter = argument» «importing parameter = argument» «changing parameter = argument» «returning value(parameter)»
parameter = argument
can be repeated if there are several parametersBaseClassName::member
syntax can be used to access an overridden member in the specified base class. Microsoft Visual C++ provides a non-standard keyword "__super" for this purpose; but this is unsupported in other compilers.option
type, which values are None
and Some x
, which could be used to represent "null reference" and "non-null reference to an object" as in other languages.==
operatorclone()
method inherited from Object
is protected, unless the class overrides the method and makes it public. If using the clone()
inherited from Object
, the class must implement the Cloneable
interface to allow cloning.Comparable
for this method to be standardized.copyWithZone:
methodcompare:
is the conventional name for the comparison method in Foundation classes. However, no formal protocol existsPrintable
protocolDebugPrintable
protocolEquatable
protocolComparable
protocolhashValue
protocol__str__()
method__repr__()
method__copy__()
method__eq__()
method__cmp__()
method__hash__()
method. Not all types are hashable (mutable types are usually not hashable)__clone()
methodx
is a class object, [x class]
returns only x
. The runtime method object_getClass(x)
will return the class of x
for all objects.