Para criar CollectionBase usamos o seguinte código:
Namespace System.Collections
A declaração pode ser feita da seguinte forma:
CollectionBase = class (System.Object, IList, ICollection, IEnumerable); abstract;
Assim, provemos a classe básica abstrata para uma coleção fortemente tipada.
Exemplo
O exemplo a seguir implementa o CollectionBase classificando e usando implementação para criar uma coleção de objetos de Int16:
Program System_Collections_CollectionBase;
uses System.Collections;
type
Int16Collection = class(CollectionBase)
public
function get_Item(index: Integer): Int16;
procedure set_Item(index: Integer; const Value: Int16);
function Add(value: Int16): Integer;
function IndexOf(value: Int16): Integer;
procedure Insert(index: Integer; value: Int16);
procedure Remove(value: Int16);
function Contains(value: Int16): Boolean;
property Item[index: Integer]: Int16
read get_Item
write set_Item;
default;
strict protected
procedure OnInsert(index: Integer;
value: System.Object); override;
procedure OnRemove(index: Integer;
value: System.Object); override;
procedure OnSet(index: Integer;
oldValue: System.Object;
newValue: System.Object); override;
procedure OnValidate(value: System.Object); override;
end;
SamplesCollectionBase = class
public
class procedure Main;
private
class procedure PrintIndexAndValues (
myCol: Int16Collection);
end;
{ SamplesCollectionBase }
class procedure SamplesCollectionBase.Main;
var
i: Integer;
myI16: Int16Collection;
begin
// Creates and initializes a new CollectionBase
myI16 := Int16Collection.Create;
myI16.Add(Int16(1));
myI16.Add(Int16(2));
myI16.Add(Int16(3));
myI16.Add(Int16(5));
myI16.Add(Int16(7));
// Displays the contents of the
//collection using the enumerator
Console.WriteLine('Initial contents of the collection:');
PrintIndexAndValues(myI16);
// Searches the collection with Contains and IndexOf
Console.WriteLine('Contains 3: ',
myI16.Contains(3));
Console.WriteLine('2 is at index .',
myI16.IndexOf(2));
Console.WriteLine;
// Inserts an element into the collection at index 3
myI16.Insert(3, (Int16(13)));
Console.WriteLine('Contents of the collection
after inserting at index 3:');
PrintIndexAndValues(myI16);
// Gets and sets an element using the index.
myI16[4] := 123;
Console.WriteLine('Contents of the collection after setting the element at index 4 to 123:');
PrintIndexAndValues(myI16);
// Removes an element from the collection
myI16.Remove((Int16(2)));
// Displays the contents of
//the collection using the index.
Console.WriteLine('Contents of the collection after removing the element 2:');
i := 0;
while (i < myI16.Count) do
begin
Console.WriteLine('[]: ', i, myI16[i]);
i := i + 1;
end;
end;
class procedure SamplesCollectionBase.PrintIndexAndValues (
myCol: Int16Collection);
var
myEnumerator: System.Collections.IEnumerator;
i: Integer;
begin
i := 0;
myEnumerator := myCol.GetEnumerator;
while myEnumerator.MoveNext do
begin
Console.WriteLine('[]: ',
i, myEnumerator.Current);
i:=i+1;
end;
Console.WriteLine;
end;
{ Int16Collection }
function Int16Collection.Add(value: Int16): Integer;
begin
Result := List.Add(value);
end;
function Int16Collection.Contains(value: Int16): Boolean;
begin
// If value is not of type Int16, this will return false.
Result := List.Contains(value);
end;
function Int16Collection.get_Item(index: Integer): Int16;
begin
Result := (Int16(List[index]));
end;
function Int16Collection.IndexOf(value: Int16): Integer;
begin
Result := List.IndexOf(value);
end;
procedure Int16Collection.Insert (
index: Integer; value: Int16);
begin
List.Insert(index, value);
end;
procedure Int16Collection.OnInsert (
index: Integer; value: System.Object);
begin
if (value.GetType <> System.Type.GetType('System.Int16'))
then
raise ArgumentException.Create (
'value must be of type Int16.', 'value');
end;
procedure Int16Collection.OnRemove (
index: Integer; value: System.Object);
begin
if (value.GetType <> System.Type.GetType('System.Int16'))
then
raise ArgumentException.Create (
'value must be of type Int16.', 'value');
end;
procedure Int16Collection.OnSet (
index: Integer; oldValue, newValue: System.Object);
begin
if (newValue.GetType <> System.Type.GetType('System.Int16'))
then
raise ArgumentException.Create (
'newValue must be of type Int16.', 'newValue');
end;
procedure Int16Collection.OnValidate (value: System.Object);
begin
if (value.GetType <> System.Type.GetType('System.Int16'))
then
raise ArgumentException.Create (
'value must be of type Int16.');
end;
procedure Int16Collection.Remove(value: Int16);
begin
List.Remove(value);
end;
procedure Int16Collection.set_Item (
index: Integer; const Value: Int16);
begin
List[index] := value;
end;
//test program
begin
SamplesCollectionBase.Main;
end.
Como saída teremos:
Conteúdos iniciais da coleção:
[0]: 1
[1]: 2
[2]: 3
[3]: 5
[4]: 7
Contains 3: True
2 is at index 1.
Contents of the collection after
inserting at index 3:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 5
[5]: 7
Contents of the collection after
setting the element at index 4 to 123:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 123
[5]: 7
Contents of the collection
after removing the element 2:
[0]: 1
[1]: 3
[2]: 13
[3]: 123
[4]: 7
