6.105 Object

Defined in namespace Smalltalk

Category: Language-Implementation

I am the root of the Smalltalk class system. All classes in the system are subclasses of me.

6.105.1 Object: built ins		(instance)
6.105.2 Object: change and update		(instance)
6.105.3 Object: class type methods		(instance)
6.105.4 Object: copying		(instance)
6.105.5 Object: debugging		(instance)
6.105.6 Object: dependents access		(instance)
6.105.7 Object: error raising		(instance)
6.105.8 Object: finalization		(instance)
6.105.9 Object: printing		(instance)
6.105.10 Object: Relational operators		(instance)
6.105.11 Object: saving and loading		(instance)
6.105.12 Object: storing		(instance)
6.105.13 Object: syntax shortcuts		(instance)
6.105.14 Object: testing functionality		(instance)
6.105.15 Object: VM callbacks		(instance)

6.105.1 Object: built ins

= arg

Answer whether the receiver is equal to arg. The equality test is by default the same as that for equal objects. = must not fail; answer false if the receiver cannot be compared to arg

== arg

Answer whether the receiver is the same object as arg. This is a very fast test and is called 'identity'

addToBeFinalized

Add the object to the list of objects to be finalized when there are no more references to them

asOop

Answer the object index associated to the receiver. The object index doesn't change when garbage collection is performed.

at: anIndex

Answer the index-th indexed instance variable of the receiver

at: anIndex put: value

Store value in the index-th indexed instance variable of the receiver

basicAt: anIndex

Answer the index-th indexed instance variable of the receiver. This method must not be overridden, override at: instead

basicAt: anIndex put: value

Store value in the index-th indexed instance variable of the receiver This method must not be overridden, override at:put: instead

basicPrint

Print a basic representation of the receiver

basicSize

Answer the number of indexed instance variable in the receiver

become: otherObject

Change all references to the receiver into references to otherObject. Depending on the implementation, references to otherObject might or might not be transformed into the receiver (respectively, 'two-way become' and 'one-way become'). Implementations doing one-way become answer the receiver (so that it is not lost). Most implementations doing two-way become answer otherObject, but this is not assured - so do answer the receiver for consistency. GNU Smalltalk does two-way become and answers otherObject, but this might change in future versions: programs should not rely on the behavior and results of #become: .

changeClassTo: aBehavior

Mutate the class of the receiver to be aBehavior. Note: Tacitly assumes that the structure is the same for the original and new class!!

checkIndexableBounds: index

Private - Check the reason why an access to the given indexed instance variable failed

checkIndexableBounds: index put: object

Private - Check the reason why a store to the given indexed instance variable failed

class

Answer the class to which the receiver belongs

halt

Called to enter the debugger

hash

Answer an hash value for the receiver. This hash value is ok for objects that do not redefine ==.

identityHash

Answer an hash value for the receiver. This method must not be overridden

instVarAt: index

Answer the index-th instance variable of the receiver. This method must not be overridden.

instVarAt: index put: value

Store value in the index-th instance variable of the receiver. This method must not be overridden.

isReadOnly

Answer whether the object's indexed instance variables can be written

makeFixed

Avoid that the receiver moves in memory across garbage collections.

makeReadOnly: aBoolean

Set whether the object's indexed instance variables can be written

makeWeak

Make the object a 'weak' one. When an object is only referenced by weak objects, it is collected and the slots in the weak objects are changed to nils by the VM

mark: aSymbol

Private - use this method to mark code which needs to be reworked, removed, etc. You can then find all senders of #mark: to find all marked methods or you can look for all senders of the symbol that you sent to #mark: to find a category of marked methods.

nextInstance

Private - answer another instance of the receiver's class, or nil if the entire object table has been walked

notYetImplemented

Called when a method defined by a class is not yet implemented, but is going to be

perform: selectorOrMessageOrMethod

Send the unary message named selectorOrMessageOrMethod (if a Symbol) to the receiver, or the message and arguments it identifies (if a Message or DirectedMessage), or finally execute the method within the receiver (if a CompiledMethod). In the last case, the method need not reside on the hierarchy from the receiver's class to Object -- it need not reside at all in a MethodDictionary, in fact -- but doing bad things will compromise stability of the Smalltalk virtual machine (and don't blame anybody but yourself). This method should not be overridden

perform: selectorOrMethod with: arg1

Send the message named selectorOrMethod (if a Symbol) to the receiver, passing arg1 to it, or execute the method within the receiver (if a CompiledMethod). In the latter case, the method need not reside on the hierarchy from the receiver's class to Object -- it need not reside at all in a MethodDictionary, in fact -- but doing bad things will compromise stability of the Smalltalk virtual machine (and don't blame anybody but yourself). This method should not be overridden

perform: selectorOrMethod with: arg1 with: arg2

Send the message named selectorOrMethod (if a Symbol) to the receiver, passing arg1 and arg2 to it, or execute the method within the receiver (if a CompiledMethod). In the latter case, the method need not reside on the hierarchy from the receiver's class to Object -- it need not reside at all in a MethodDictionary, in fact -- but doing bad things will compromise stability of the Smalltalk virtual machine (and don't blame anybody but yourself). This method should not be overridden

perform: selectorOrMethod with: arg1 with: arg2 with: arg3

Send the message named selectorOrMethod (if a Symbol) to the receiver, passing the other arguments to it, or execute the method within the receiver (if a CompiledMethod). In the latter case, the method need not reside on the hierarchy from the receiver's class to Object -- it need not reside at all in a MethodDictionary, in fact -- but doing bad things will compromise stability of the Smalltalk virtual machine (and don't blame anybody but yourself). This method should not be overridden

perform: selectorOrMethod withArguments: argumentsArray

Send the message named selectorOrMethod (if a Symbol) to the receiver, passing the elements of argumentsArray as parameters, or execute the method within the receiver (if a CompiledMethod). In the latter case, the method need not reside on the hierarchy from the receiver's class to Object -- it need not reside at all in a MethodDictionary, in fact -- but doing bad things will compromise stability of the Smalltalk virtual machine (and don't blame anybody but yourself). This method should not be overridden

primError: message

This might start the debugger... Note that we use #basicPrint 'cause #printOn: might invoke an error.

primitiveFailed

Called when a VM primitive fails

removeToBeFinalized

Remove the object from the list of objects to be finalized when there are no more references to them

shouldNotImplement

Called when objects belonging to a class should not answer a selector defined by a superclass

size

Answer the number of indexed instance variable in the receiver

specialBasicAt: index

Similar to basicAt: but without bounds checking. This method is used to support instance mutation when an instance's class definition is changed. This method must not be overriddent

subclassResponsibility

Called when a method defined by a class should be overridden in a subclass

6.105.2 Object: change and update

broadcast: aSymbol

Send the unary message aSymbol to each of the receiver's dependents

broadcast: aSymbol with: anObject

Send the message aSymbol to each of the receiver's dependents, passing anObject

broadcast: aSymbol with: arg1 with: arg2

Send the message aSymbol to each of the receiver's dependents, passing arg1 and arg2 as parameters

broadcast: aSymbol withArguments: anArray

Send the message aSymbol to each of the receiver's dependents, passing the parameters in anArray

broadcast: aSymbol withBlock: aBlock

Send the message aSymbol to each of the receiver's dependents, passing the result of evaluating aBlock with each dependent as the parameter

changed

Send update: for each of the receiver's dependents, passing them the receiver

changed: aParameter

Send update: for each of the receiver's dependents, passing them aParameter

update: aParameter

Default behavior is to do nothing. Called by #changed and #changed:

6.105.3 Object: class type methods

species

This method has no unique definition. Generally speaking, methods which always return the same type usually don't use #class, but #species. For example, a PositionableStream's species is the class of the collection on which it is streaming (used by upTo:, upToAll:, upToEnd). Stream uses species for obtaining the class of next:'s return value, Collection uses it in its #copyEmpty: message, which in turn is used by all collection-re- turning methods. An Interval's species is Array (used by collect:, select:, reject:, etc.).

yourself

Answer the receiver

6.105.4 Object: copying

copy

Returns a shallow copy of the receiver (the instance variables are not copied). The shallow copy receives the message postCopy and the result of postCopy is passed back.

deepCopy

Returns a deep copy of the receiver (the instance variables are copies of the receiver's instance variables)

postCopy

Performs any changes required to do on a copied object. This is the place where one could, for example, put code to replace objects with copies of the objects

shallowCopy

Returns a shallow copy of the receiver (the instance variables are not copied)

6.105.5 Object: debugging

breakpoint: context return: return

Called back by the system. Must return the value passed through the second parameter

inspect

Print all the instance variables of the receiver on the Transcript

validSize

Answer how many elements in the receiver should be inspected

6.105.6 Object: dependents access

addDependent: anObject

Add anObject to the set of the receiver's dependents. Important: if an object has dependents, it won't be garbage collected.

dependents

Answer a collection of the receiver's dependents.

release

Remove all of the receiver's dependents from the set and allow the receiver to be garbage collected.

removeDependent: anObject

Remove anObject to the set of the receiver's dependents. No problem if anObject is not in the set of the receiver's dependents.

6.105.7 Object: error raising

doesNotUnderstand: aMessage

Called by the system when a selector was not found. message is a Message containing information on the receiver

error: message

Display a walkback for the receiver, with the given error message. Signal an `Error' exception (you can trap it the old way too, with `ExError'

halt: message

Display a walkback for the receiver, with the given error message. Signal an `Halt' exception (you can trap it the old way too, with `ExHalt')

6.105.8 Object: finalization

finalize

Do nothing by default

6.105.9 Object: printing

basicPrintNl

Print a basic representation of the receiver, followed by a new line.

basicPrintOn: aStream

Print a represention of the receiver on aStream

display

Print a represention of the receiver on the Transcript (stdout the GUI is not active). For most objects this is simply its #print representation, but for strings and characters, superfluous dollars or extra pair of quotes are stripped.

displayNl

Print a represention of the receiver, then put a new line on the Transcript (stdout the GUI is not active). For most objects this is simply its #printNl representation, but for strings and characters, superfluous dollars or extra pair of quotes are stripped.

displayOn: aStream

Print a represention of the receiver on aStream. For most objects this is simply its #printOn: representation, but for strings and characters, superfluous dollars or extra pair of quotes are stripped.

displayString

Answer a String representing the receiver. For most objects this is simply its #printString, but for strings and characters, superfluous dollars or extra pair of quotes are stripped.

print

Print a represention of the receiver on the Transcript (stdout the GUI is not active)

printNl

Print a represention of the receiver on stdout, put a new line the Transcript (stdout the GUI is not active)

printOn: aStream

Print a represention of the receiver on aStream

printString

Answer a String representing the receiver

6.105.10 Object: Relational operators

~= anObject

Answer whether the receiver and anObject are not equal

~~ anObject

Answer whether the receiver and anObject are not the same object

6.105.11 Object: saving and loading

binaryRepresentationObject

This method must be implemented if PluggableProxies are used with the receiver's class. The default implementation raises an exception.

postLoad

Called after loading an object; must restore it to the state before `preStore' was called. Do nothing by default

postStore

Called after an object is dumped; must restore it to the state before `preStore' was called. Call #postLoad by default

preStore

Called before dumping an object; it must *change* it (it must not answer a new object) if necessary. Do nothing by default

reconstructOriginalObject

Used if an instance of the receiver's class is returned as the #binaryRepresentationObject of another object. The default implementation raises an exception.

6.105.12 Object: storing

store

Put a String of Smalltalk code compiling to the receiver on the Transcript (stdout the GUI is not active)

storeNl

Put a String of Smalltalk code compiling to the receiver, followed by a new line, on the Transcript (stdout the GUI is not active)

storeOn: aStream

Put Smalltalk code compiling to the receiver on aStream

storeString

Answer a String of Smalltalk code compiling to the receiver

6.105.13 Object: syntax shortcuts

-> anObject

Creates a new instance of Association with the receiver being the key and the argument becoming the value

6.105.14 Object: testing functionality

ifNil: nilBlock

Evaluate nilBlock if the receiver is nil, else answer self

ifNil: nilBlock ifNotNil: notNilBlock

Evaluate nilBlock if the receiver is nil, else evaluate notNilBlock, passing the receiver.

ifNotNil: notNilBlock

Evaluate notNiilBlock if the receiver is not nil, passing the receiver. Else answer nil.

ifNotNil: notNilBlock ifNil: nilBlock

Evaluate nilBlock if the receiver is nil, else evaluate notNilBlock, passing the receiver.

isArray

Answer `false'.

isBehavior

Answer `false'.

isCharacter

Answer `false'.

isCharacterArray

Answer `false'.

isClass

Answer `false'.

isFloat

Answer `false'.

isInteger

Answer `false'.

isKindOf: aClass

Answer whether the receiver's class is aClass or a subclass of aClass

isMemberOf: aClass

Returns true if the receiver is an instance of the class 'aClass'

isMeta

Same as isMetaclass

isMetaclass

Answer `false'.

isMetaClass

Same as isMetaclass

isNamespace

Answer `false'.

isNil

Answer whether the receiver is nil

isNumber

Answer `false'.

isSmallInteger

Answer `false'.

isString

Answer `false'.

isSymbol

Answer `false'.

notNil

Answer whether the receiver is not nil

respondsTo: aSymbol

Returns true if the receiver understands the given selector

6.105.15 Object: VM callbacks

badReturnError

Called back when a block performs a bad return

mustBeBoolean

Called by the system when ifTrue:*, ifFalse:*, and: or or: are sent to anything but a boolean

noRunnableProcess

Called back when all processes are suspended

userInterrupt

Called back when the user presses Ctrl-Break