TGraphObjectList.md

TGraphObjectList = class(TPersistent)

This class holds a list of TGraphObject objects.

The instances of TGraphObjectList class do not own their holding objects.

Properties

In addition to the properties of the TPersistent class, the TGraphObjectList class provides the following properties:

• public Capacity: Integer
  Specifies the allocated size of the array of items maintained by the list.

• public Count: Integer (read-only)
  Gets the number of entries in the list that are in use.

• public Items[Index: Integer]: TGraphObject (read-only)
  Gets an item in the list by its zero-based index.

Methods

In addition to the methods of the TPersistent class, the TGraphObjectList class has the following public methods:

• procedure Clear;
  Deletes all the items from the list.

• function Add(Item: TGraphObject): Integer;
  Adds a new item at the end of the list.

  Parameter	Description
  Item	The item to be added

  Returns the index of the added item.

• procedure Insert(Index: Integer; Item: TGraphObject);
  Inserts a new item at a specified index of the list.

  Parameter	Description
  Index	The zero-based index of the new item in the list
  Item	The item to be added

• procedure Delete(Index: Integer);
  Removes an item at a specified index from the list.

  Parameter	Description
  Index	The zero-based index of the item to be removed

• function Remove(Item: TGraphObject): Integer;
  Removes a specified item from the list.

  Parameter	Description
  Item	The item to be removed

  Returns the index of the removed item if the item is found; otherwise, returns -1.

• procedure Move(CurIndex, NewIndex: Integer);
  Changes the position of an item in the list.

  Parameter	Description
  CurIndex	The zero-based index of the item to be moved
  NewIndex	The new zero-based index of the item in the list

• function IndexOf(Item: TGraphObject): Integer;
  Locates the index of an item in the list.

  Returns the index of the item if the item is found; otherwise, returns -1.

• function First: TGraphObject;
  Initializes the forward enumeration of the list and returns the first item.

  Return the first item in the list if the list is not empty; otherwise, returns nil.

• function Last: TGraphObject;
  Initializes the backward enumeration of the list and returns the last item.

  Return the last item of the list if the list is not empty; otherwise, returns nil.

• function Next: TGraphObject;
  During enumeration, returns the next item of a forward enumeration. Before calling this method for the first time, the First method should be called.

  Returns next item in the list or nil if end of the list is reached.

• function Prior: TGraphObject;
  During enumeration, returns the next item of a backward enumeration. Before calling this method for the first time, the Last method should be called.

  Returns previous item in the list or nil if begin of the list is reached.

• function Push: Boolean;
  Saves the current enumeration state.

  Returns true if an enumeration state is saved; otherwise, false.

• function Pop: Boolean;
  Restores the last saved enumeration state.

  Returns true if an enumeration state is restored; otherwise, false.

Events

The TGraphObjectList class has the following event:

• OnChange: TGraphObjectListEvent
TGraphObjectListEvent = procedure(Sender: TObject; GraphObject: TGraphObject; Action: TGraphObjectListAction) of object
  Occurs when the list has been changed.

  Parameter	Description
  Sender	The TGraphObjectList instance that generated the event
  GraphObject	The TGraphObject instance that was target of the change
  Action	The action that caused the event

  The action parameter can have one of the following values:

  Value	Description
  glAdded	The item has been added to the list
  glRemoved	The item has been removed from the list
  glReordered	The position of the item in the list has been changed