TBoldAbstractListHandle¶

Superclass for all list handles.

Declaration¶

TBoldAbstractListHandle = class(TBoldRootedHandle)

Hierarchy¶

TComponent
TBoldSubscribableComponent
TBoldElementHandle
TBoldNonSystemHandle
TBoldRootedHandle
TBoldAbstractListHandle
Direct subclasses
TBoldCursorHandle

Description¶

TBoldAbstractListHandle is an abstract superclass for handles with a cursor-type behaviour. Its purpose is to represent a list of elements, and a position in that list.

It is an extension of TBoldElementHandle in that it really has two values, the List property, and the Value property, where this Value property is effectively List[CurrentIndex]. There are a number of visual controls, notably TBoldNavigator, TBoldGrid and TBoldListBox that connect to a list handle. They are a bit special compared to other controls in that they not only manipulate values in the Object-Space, but also can set CurrentIndex, which resides in the listhandle itself.

The handle is designed to make Chained Evaluation as natural as possible.

Properties¶

Name	Summary	Notes
Count	Number of elements in the list.	read-only
CurrentBoldObject	CurrentElement as TBoldObject .	read-only
CurrentElement	Current element in list.	read-only
CurrentIndex	Current position in list.
HasNext	Use HasNext to determine if at end of list.	read-only
HasPrior	Indicates whether it is possible to move backward in the list.	read-only
List	List represented by handle.	read-only
ListElementType	Type of elements in List.	read-only
ListType	The "Best Available" type	read-only
MutableList	Returns a list that is possible to change.	read-only
MutableObjectList	Returns the MutableList as a TBoldObjectList.	read-only
ObjectList	Returns the List as a TBoldObjectList.	read-only
StaticListType	The list type of the StaticBoldType	read-only

Count¶

property Count: Integer;

This is mostly equivalent to List.Count, with the added provision of being 0 if List is **nil**.

CurrentBoldObject¶

property CurrentBoldObject: TBoldObject;

If CurrentElement is a TBoldObject, then this property will be that value, type cast to a TBoldObject, otherwise an exception will be raised.

CurrentElement¶

property CurrentElement: TBoldElement;

CurrentElement returns the element that is current in the list. This will be the same as the value property of the handle

CurrentIndex¶

property CurrentIndex: Integer;

This property can be read to find the current index of the listhandle, or set programmatically to change the current index in the list.

See Also

HasNext¶

property HasNext: Boolean;

HasNext is a concept similar to Eof, but returning true while there is a next element.

Example:

aListHandle.First; while aListHandle.HasNext do aListHandle.Next;

HasPrior¶

property HasPrior: Boolean;

This is true if the CurrentIndex property is greater than 0.

List¶

property List: TBoldList;

List represented by handle.

ListElementType¶

property ListElementType: TBoldElementTypeInfo;

This is the type of the elements of the list.

Note

This is subtly different from BoldType. It will be equivalent to `BoldType` when (`Value <> nil`) or (`List = nil`). However if there is list, but (`Value = nil`), either because the list is empty, or (`CurrentIndex = -1`), `ListElementType` will be the type of the elements in that list, rather than `StaticBoldType`.

ListType¶

property ListType: TBoldListTypeInfo;

The type of the list, if available. StaticListType, otherwise.

MutableList¶

property MutableList: TBoldList;

MutableObjectList will return a list that is possible to change. If the List is mutable, it will be used.

MutableObjectList¶

property MutableObjectList: TBoldObjectList;

MutableObjectList will determine if the MutableList is a TBoldObjectList. If so the the list will be returned as such, otherwise **nil** will be returned

ObjectList¶

property ObjectList: TBoldObjectList;

ObjectList will determine if the List is a TBoldObjectList. If so, the list will be returned as such, otherwise **nil** will be returned.

StaticListType¶

property StaticListType: TBoldListTypeInfo;

The list type of the StaticBoldType

Methods¶

Name	Summary	Notes
First	Sets CurrentIndex to 0.
GetCurrentElement	Get-method for the CurrentElement property	protected, abstract
GetCurrentIndex	Get-method for the CurrentIndex property	protected, abstract
GetList	Get-method for the List property	protected, abstract
GetMutableList	Get-method for the MutableList property	protected, virtual
Last	Set CurrentIndex to Count - 1.
Next	Move forward in list
Prior	Move backwards in the list
RemoveCurrentElement	Remove current element from list
SetCurrentIndex	Set-method for the CurrentIndex property	protected, abstract

First¶

procedure First;

Sets CurrentIndex to 0.

GetCurrentElement¶

function GetCurrentElement: TBoldElement; virtual; abstract;

Get-method for the CurrentElement property

GetCurrentIndex¶

function GetCurrentIndex: Integer; virtual; abstract;

Get-method for the CurrentIndex property

GetList¶

function GetList: TBoldList; virtual; abstract;

Get-method for the List property

GetMutableList¶

function GetMutableList: TBoldList; virtual;

Get-method for the MutableList property

Last¶

procedure Last;

Set CurrentIndex to Count - 1.

Next¶

procedure Next;

Increases CurrentIndex if it is less than Count.

Prior¶

procedure Prior;

Decrease CurrentIndex if it is more than 0.

RemoveCurrentElement¶

procedure RemoveCurrentElement;

Remove the CurrentElement from the List. If the list is a class-list (such as Person.allInstances), this will result in the object being deleted.

SetCurrentIndex¶

procedure SetCurrentIndex(Value: Integer); virtual; abstract;

Set-method for the CurrentIndex property

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