Classes unit

This documentation describes the FPC classes unit. The Classes unit contains basic classes for the Free Component Library (FCL):

• a TList class for maintaining lists of pointers,
• TStringList for lists of strings,
• TCollection to manage collections of objects
• TStream classes to support streaming.

Furthermore it introduces methods for object persistence, and classes that understand an owner-owned relationship, with automatic memory management.

Classes and records

ComponentPlatformsAttribute	class
EBitsError	class	Exception raised when an error occurs in a method of .
EClassNotFound	class	Exception raised when an unknown class is referenced in a streamed component.
EComponentError	class	Exception raised when an error occurs in the component registration routines.
EFCreateError	class	Exception raised when an error occurred during creation of a stream.
EFilerError	class	Exception raised by the component streaming system if an error occurs.
EFOpenError	class	Exception raised when an error occurred during creation of a .
EInvalidImage	class	Exception raised when the resource header needed for streaming of a component is invalid.
EInvalidOperation	class	Exception raised when an invalid operation is performed. Obsolete.
EMethodNotFound	class	This exception is no longer used.
EObserver	class	Error raised when an observer error occurs.
EObserverException	class
EOutOfResources	class	Exception raised when the system is out of resources.
EParserError	class	Exception raised when an error occurs during the parsing of streams.
EReadError	class	Exception raised if an error occurs while reading from a stream.
EResNotFound	class	Exception raised when a resource, needed to initialize a component, is not found.
EStreamError	class	Exception raised when an error occurs during read or write operations on a stream.
EStringListError	class	Exception raised when an error occurs in a method of .
EThread	class	Thread error exception.
EThreadDestroyCalled	class	Exception raised when a thread is destroyed illegally.
EThreadExternalException	class	Exception raised when an invalid operation is attempted on an external thread.
EWriteError	class	Exception raised when an error occurs during writing to a stream.
IControlValueObserver	interface
IDesignerNotify	interface	Designer notification interface.
IEditFormatLink	interface
IEditGridLinkObserver	interface
IEditLinkObserver	interface
IFPObserved	interface	Interface implemented by an object that can be observed.
IFPObserver	interface	Interface for an object to observe other objects.
IInterfaceComponentReference	interface	Interface for checking component references.
IInterfaceList	interface	Interface for maintaining a list of interfaces.
IInterfaceListEx	interface
IIteratorLinkObserver	interface
IMultiCastObserver	interface
IObserver	interface
IObserverTrack	interface
IPositionLinkObserver	interface
IPositionLinkObserver170	interface
ISingleCastObserver	interface
IStreamPersist	interface	Persistence streaming interface.
IStringsAdapter	interface	IStringsAdapter Interface declaration.
IVCLComObject	interface	Com automation Object interface.
ObservableMemberAttribute	class
TAbstractObjectReader	class	Abstract driver class to read stored component data.
TAbstractObjectWriter	class	Abstract driver class for writing component data.
TBasicAction	class	Abstract base class for all Actions.
TBasicActionLink	class	Link between actions and action clients (e.g. controls).
TBinaryObjectReader	class	Driver class descendant which reads component data stored in binary format.
TBinaryObjectWriter	class	Driver class which stores component data in binary form.
TBits	class	Class to store collections of bits (binary values that can be 0 or 1).
TBytesStream	class	Stream of bytes.
TCollection	class	Base class to manage collections of named objects.
TCollectionEnumerator	class	Implements IEnumerator for the TCollection class.
TCollectionItem	class	Basic object that is managed by a class.
TComponent	class	Base class for all components that need owner-owned functionality.
TComponentEnumerator	class	Implements IEnumerator for the TComponent class.
TCustomMemoryStream	class	Abstract stream that stores its data in memory.
TDataModule	class	Container for non-visual components.
TFiler	class	Class responsible for streaming of components.
TFileStream	class	Stream that stores its data in a named file on disk.
TFPList	class	Class to manage collections of pointers.
TFPListEnumerator	class	Implements IEnumerator for the TFPList class.
THandleStream	class	Base class for streams that are identified by an OS handle.
TIdentMapEntry	record	Record used when associating names with integer values.
TInterfacedPersistent	class	TPersistent descendant which implements the IInterface interface.
TInterfaceList	class	Standard implementation of the IInterfaceList interface.
TInterfaceListEnumerator	class	Implements IEnumerator for the TInterfaceList class.
TLinkObservers	class
TList	class	Class to manage collections of pointers.
TListEnumerator	class	Implements IEnumerator for the TList class.
TMemoryStream	class	Standard implementation of a stream that stores its data in memory.
TObserverMapping	class
TObservers	class
TOwnedCollection	class	TCollection descendant which maintains owner information.
TOwnerStream	class	Stream which uses a second stream as a source.
TParser	class	Class to parse the contents of a stream containing text data.
TPersistent	class	Base class for streaming system and persistent properties.
TProxyAggregateStream	class
TProxyStream	class	Proxy stream for the IStream interface.
TRawByteStringStream	class	TBytesStream descendent with some single-byte string methods.
TReader	class	Generic reader object which reads component data from any given source.
TRecall	class	Helper class for storing published properties.
TResourceStream	class	Stream that reads its data from a resource object.
TStream	class	Base class for streams.
TStreamAdapter	class	Implements IStream for TStream descendants.
TStringItem	record	The TStringItem is used to store the string and object items in a string list instance. It should never be used directly.
TStringList	class	Standard implementation of the class.
TStrings	class	Class to manage arrays or collections of strings.
TStringsEnumerator	class	Implements IEnumerator for the TStrings class.
TStringStream	class	Stream that stores its data in a string.
TTextObjectWriter	class	Driver class which stores component data in text format.
TThread	class	Abstract Thread class.
TThreadList	class	Thread-safe list object.
TWriter	class	Object to write component data to an arbitrary format.

Procedures and functions

ActivateClassGroup	function	Activates a class group.
BeginGlobalLoading	procedure	Not yet implemented.
BinToHex	procedure	Convert a binary buffer to a hexadecimal string.
Bounds	function	Returns a TRect structure with the bounding rect of the given location and size.
CheckSynchronize	function	Check whether there are any synchronize calls in the synchronize queue.
ClassGroupOf	function	Returns the class group to which an instance or class belongs.
CollectionsEqual	function	Returns True if two collections are equal.
EndGlobalLoading	procedure	Not yet implemented.
ExtractStrings	function	Split a string in different words.
FindClass	function	Returns the class pointer of a class with given name.
FindGlobalComponent	function	Callback used when a component must be found.
FindIdentToInt	function	Return the string to integer converter for an integer type.
FindIntToIdent	function	Return the integer to string converter for an integer type.
FindNestedComponent	function	Finds the component with name path starting at the indicated root component.
GetClass	function	Returns the class pointer of a class with given name.
GetFixupInstanceNames	procedure	Returns the names of elements that need to be resolved for the root component, whose reference contains ReferenceRootName.
GetFixupReferenceNames	procedure	Returns the names of elements that need to be resolved for the root component.
GlobalFixupReferences	procedure	Called to resolve unresolved references after forms are loaded.
GroupDescendentsWith	procedure	Provided for Delphi compatibility.
HexToBin	function	Convert a hexadecimal string to a binary buffer.
IdentToInt	function	Looks up an integer value in a integer-to-identifier map list.
IfThen	function
InitComponentRes	function	Provided for Delphi compatibility only.
InitInheritedComponent	function	Initializes a component descending from RootAncestor.
IntToIdent	function	Looks up an identifier for an integer value in a identifier-to-integer map list.
InvalidPoint	function	Check whether a point is invalid.
IsUniqueGlobalComponentName	function
LineStart	function	Finds the start of a line in Buffer before BufPos.
NotifyGlobalLoading	procedure	Not yet implemented.
ObjectBinaryToText	procedure	Converts an object stream from a binary to a text format.
ObjectResourceToText	procedure	Converts an object stream from a (windows) resource to a text format.
ObjectTextToBinary	procedure	Converts an object stream from a text to a binary format.
ObjectTextToResource	procedure	Converts an object stream from a text to a (windows) resource format.
Point	function	Returns a TPoint record with the given coordinates.
PointsEqual	function	Check whether two TPoint variables are equal.
ReadComponentDeltaRes	function
ReadComponentRes	function	Read component properties from a resource in the current module.
ReadComponentResEx	function	Read component properties from a resource in the specified module.
ReadComponentResFile	function	Read component properties from a specified resource file.
Rect	function	Returns a TRect record with the given coordinates.
RedirectFixupReferences	procedure	Redirects references under the root object from OldRootName to NewRootName.
RegisterClass	procedure	Registers a class with the streaming system.
RegisterClassAlias	procedure	Registers a class alias with the streaming system.
RegisterClasses	procedure	Registers multiple classes with the streaming system.
RegisterComponents	procedure	Registers components for the component palette.
RegisterFindGlobalComponentProc	procedure	Register a component searching handler.
RegisterInitComponentHandler	procedure	Register a component initialization handler.
RegisterIntegerConsts	procedure	Registers some integer-to-identifier mappings.
RegisterNoIcon	procedure	Registers components that have no icon on the component palette.
RegisterNonActiveX	procedure	Register non-activex component.
RemoveFixupReferences	procedure	Removes references to rootname from the fixup list.
RemoveFixups	procedure	Removes Instance from the fixup list.
SmallPoint	function	Returns a TSmallPoint record with the given coordinates.
StartClassGroup	procedure	Start new class group.
TestStreamFormat	function
UnRegisterClass	procedure	Unregisters a class from the streaming system.
UnRegisterClasses	procedure	Unregisters multiple classes from the streaming system.
UnregisterFindGlobalComponentProc	procedure	Remove a previously registered component searching handler.
UnRegisterModuleClasses	procedure	Unregisters classes registered by module.
WriteComponentResFile	procedure	Write component properties to a specified resource file.

Types

EListError	type	Exception raised when an error occurs in lists handling.
HMODULE	type	Special type for handling modules.
HRSRC	type	Type to manage resources.
PBitsBase	type
PPointerList	type	Pointer to an array of pointers.
PStringItem	type	Pointer to a record.
PStringItemList	type	Pointer to a .
TActionEvent	procedure type
TActiveXRegType	enumeration	Used when registering ActveX component types.
TAlignment	enumeration	Type to specify text alignment in controls that display text.
TAncestorNotFoundEvent	procedure type	This event occurs when an ancestor component cannot be found.
TBasicActionClass	type	class reference.
TBasicActionLinkClass	type	class reference.
TBiDiMode	enumeration	BIDI description.
TBitsBase	type
TBitsBaseSigned	type
TBitsOpCallback	procedure type
TBitsOpTruth	type
TCollectionItemClass	type	Class reference for .
TCollectionNotification	enumeration	Collection change notification enumeration.
TCollectionSortCompare	procedure type	Callback to sort collection items.
TCollectionSortCompare_Context	procedure type
TComponentClass	type	Class of TComponent.
TComponentName	type	Special type for component names.
TComponentState	set	Indicates the state of the component during the streaming process.
TComponentStyle	set	Describes the style of the component.
TCreateComponentEvent	procedure type	Event handler type, occurs when a component instance must be created when a component is read from a stream.
TDataModuleClass	type	Class pointer for TDataModule.
TDuplicates	type	Type to describe what to do with duplicate values in a .
TExceptionClass	type	Class of Exception.
TFilerFlag	enumeration	Flags used by the class.
TFilerFlags	set	Set of .
TFindAncestorEvent	procedure type	Event that occurs w.
TFindComponentClassEvent	procedure type	Event handler type, occurs when a component class pointer must be found when reading a component from a stream.
TFindComponentClassExEvent	procedure type
TFindGlobalComponent	procedure type	Callback type to search for a component.
TFindMethodEvent	procedure type	Occurs when the streaming process needs to locate a method.
TFPObservedOperation	enumeration	Operation which is reported to an observer.
TGetChildProc	procedure type	Callback used when obtaining child components.
TGetDeltaStreamsEvent	procedure type
TGetStreamProc	procedure type
TGetStrProc	procedure type	Event for retrieving string values.
THandle	type	Type to manage streams.
THelpContext	type	Range type to specify help contexts.
THelpEvent	procedure type	Special event for display of online help.
THelpType	enumeration	Enumeration type specifying the kind of help requested.
THintEvent	procedure type
TIdentToInt	procedure type	Callback for converting identifiers to integers.
TIInterfaceArray	type
TInitComponentHandler	procedure type	Callback type for RegisterInitComponentHandler.
TIntToIdent	procedure type	Callback for converting integers to identifiers.
TIsUniqueGlobalComponentName	procedure type
TLeftRight	type	Subrange type based on TAlignment.
TListAssignOp	enumeration	List assign operation.
TListCallback	type	Method callback type for TFPList.ForEachCall.
TListNotification	enumeration	Kind of list notification event.
TListSortCompare	procedure type	Callback type for the list sort algorithm.
TListStaticCallback	type	Static method callback type for TFPList.ForEachCall.
TMissingNameValueSeparatorAction	enumeration	What to to with Name=value pairs if the separator is missing.
TMissingNameValueSeparatorActions	set	Set of TMissingNameValueSeparatorAction.
TNotifyCallBack	procedure type	Thread termination callback handler.
TNotifyEvent	procedure type	Standard event handler type.
TObjectTextEncoding	enumeration	Encoding of the object text file.
TObserverGetCurrentEvent	procedure type
TObserverToggleEvent	procedure type
TOperation	enumeration	Operation of which a component is notified.
TPersistentClass	type	Class reference type for .
TPlatformIds	type
TPoint	type	Special type to handle a fake position.
TPointerList	type	Type for an Array of pointers.
TPropertyNotFoundEvent	procedure type	Callback for the event.
TReadComponentsProc	procedure type	Callback type when reading a component from a stream.
TReaderError	procedure type	Event handler type, called when an error occurs during the streaming.
TReaderProc	procedure type	Reader procedure used by DefineProperties.
TReadWriteStringPropertyEvent	procedure type	Callback for the event handler.
TRect	type	Describes a rectangle.
TReferenceNameEvent	procedure type	Occurs when a named object needs to be looked up.
TSeekOrigin	enumeration	Specifies the origin of the method.
TSetMethodPropertyEvent	procedure type	Callback for the event.
TSetNameEvent	procedure type	Occurs when the reader needs to set a component's name.
TShiftState	set	Indicates what special keys were pressed in combination with a normal key.
TShiftStateEnum	enumeration	Keyboard/Mouse shift state enumerator.
TShortCut	type	Enumeration type to identify shortcut key combinations.
TSmallPoint	type	Type to describe point in a small plane.
TStreamOriginalFormat	enumeration
TStreamOwnership	enumeration	Determines the ownership of a TStreamAdapter.
TStreamProc	procedure type	Procedure type used in streaming.
TStringItemList	type	Array of records.
TStringListSortCompare	procedure type	Callback type used in stringlist compares.
TStringsClass	type	Class of TStrings.
TStringsFilterMethod	procedure type	Callback signature for TStrings.Filter.
TStringsForEachMethod	procedure type	Callback signature for TStrings.Foreach.
TStringsForEachMethodEx	procedure type	Callback signature for TStrings.Foreach.
TStringsForEachMethodExObj	procedure type	Callback signature for TStrings.Foreach.
TStringsMapMethod	procedure type	Reduce algorithm for TStrings.Map.
TStringsOption	enumeration	Enumeration of options used in TStrings.
TStringsOptions	set	Set of TStringsOption.
TStringsReduceMethod	procedure type	Reduce algorithm for TStrings.Reduce.
TStringsSortStyle	enumeration	Determines how the strings are sorted.
TStringsSortStyles	set	Set of TStringsSortStyle.
TSynchronizeProcVar	procedure type	Synchronize callback type.
TThreadExecuteCallBack	procedure type	Signature of procedure to execute in a thread, without status reporting.
TThreadExecuteHandler	type	Signature of method to execute in a thread, without status reporting.
TThreadExecuteStatusCallBack	procedure type	Signature of procedure to execute in a thread, with status reporting.
TThreadExecuteStatusHandler	procedure type	Signature of method to execute in a thread, with status reporting.
TThreadMethod	procedure type	Procedure variable used when synchronizing threads.
TThreadPriority	enumeration	Enumeration specifying the priority at which a thread runs.
TThreadReportStatus	procedure type	Thread status report callback prototype.
TThreadStatusNotifyCallBack	procedure type	Signature of thread status report callback.
TThreadStatusNotifyEvent	procedure type	Signature of thread status report event handler.
TTopBottom	type	Range of alignments.
TValueType	enumeration	Enumerated type used to identify the kind of streamed property.
TVerticalAlignment	enumeration	Vertical alignment type.
TWriteMethodPropertyEvent	procedure type	Callback for the event.
TWriterProc	procedure type	Writer procedure used by DefineProperties.

Constants

dupAccept	constant	Duplicate values can be added to the list.
dupError	constant	If an attempt is made to add a duplicate value to the list, an exception is raised.
dupIgnore	constant	Duplicate values will not be added to the list, but no error will be triggered.
FilerSignature	constant	Constant that is found at the start of a binary stream containing a streamed component.
FilerSignature1	constant
fmCreate	constant	creates a new file if needed.
fmOpenRead	constant	opens a file with read-only access.
fmOpenReadWrite	constant	opens a file with read-write access.
fmOpenWrite	constant	opens a file with write-only access.
MaxBitFlags	constant	Maximum number of bits in TBits collection.
MaxListSize	constant	Maximum number of elements in list.
NilHandle	constant
pfidAndroid	constant
pfidiOS	constant
pfidLinux	constant
pfidOSX	constant
pfidWindows	constant
pidAllPlatforms	constant
pidAndroidArm32	constant
pidAndroidArm64	constant
pidiOSDevice32	constant
pidiOSDevice64	constant
pidiOSSimulator32	constant
pidiOSSimulator64	constant
pidiOSSimulatorArm64	constant
pidLinux32	constant
pidLinux64	constant
pidLinuxArm32	constant
pidLinuxArm64	constant
pidOSX32	constant
pidOSX64	constant
pidOSXArm64	constant
pidWin32	constant
pidWin64	constant
pidWinARM32	constant
pidWinArm64	constant
pidWinIoT32	constant
pidWinNX32	constant
scAlt	constant	Indicates ALT key in a keyboard shortcut.
scCommand	constant
scCtrl	constant	indicates CTRL key in a keyboard shortcut.
scNone	constant	Indicates no special key is pressed in a keyboard shortcut.
scShift	constant	Indicates Shift key in a keyboard shortcut.
SGUIDObserved	constant	Observed interface GUID as a string.
SGUIDObserver	constant	Observer interface GUID as a string.
soFromBeginning	constant	Seek starts relative to the stream origin.
soFromCurrent	constant	Seek starts relative to the current position in the stream.
soFromEnd	constant	Seek starts relative to the stream end.
ssCommand	constant
toEOF	constant	Value returned by when the end of the input stream was reached.
toFloat	constant	Value returned by when a floating point value was found in the input stream.
toInteger	constant	Value returned by when an integer was found in the input stream.
toString	constant	Value returned by when a string was found in the input stream.
toSymbol	constant	Value returned by when a symbol was found in the input stream.
toWString	constant	Value returned by when a widestring was found in the input stream.

Variables

AddDataModule	variable	Handler called when a new TDataModule instance is created.
ApplicationHandleException	variable	Handler for exceptions when a TDataModule streaming error occurs.
ApplicationShowException	variable	Unused.
CreateVCLComObjectProc	variable	Called to create an instance of IVCLComObject.
DelphiCompatibleStreams	variable
GlobalNameSpace	variable	Global namespace.
IsUniqueGlobalComponentNameProc	variable
MainThreadID	variable	ID of main thread. Unused at this point.
RegisterComponentsProc	variable	Callback procedure used when handling component registration.
RegisterNoIconProc	variable	Callback procedure used when handling icon-less component registration.
RemoveDataModule	variable	Handler called when a TDataModule instance is freed.
WakeMainThread	variable	Handler which is called if a thread wants to synchronize with the main application thread.

Uses

• sysutils
• Types
• TypInfo
• rtlconsts
• sortbase