The Delphi XE2 online help (as well as the Embarcadero DocWiki) is very thin on the documentation of TObjectDictionary
(or I am too stupid to find it).
As far as I understand it, it can be used to store object instances that can be accessed via string keys (basically what was always possible with a sorted TStringList
but typesafe). But I am at a loss on how to actually declare and use it.
Any pointers?
The main difference between a TObjectDictionary
and a TDictionary
is that provides an mechanism to specify the Ownership of the keys and/or values added to the collection (dictionary), So you don't need to worry about freeing these objects.
Check this basic sample
{$APPTYPE CONSOLE}
{$R *.res}
uses
Generics.Collections,
Classes,
System.SysUtils;
Var
MyDict : TObjectDictionary<String, TStringList>;
Sl : TStringList;
begin
ReportMemoryLeaksOnShutdown:=True;
try
//here i'm creating a TObjectDictionary with the Ownership of the Values
//because in this case the values are TStringList
MyDict := TObjectDictionary<String, TStringList>.Create([doOwnsValues]);
try
//create an instance of the object to add
Sl:=TStringList.Create;
//fill some foo data
Sl.Add('Foo 1');
Sl.Add('Foo 2');
Sl.Add('Foo 3');
//Add to dictionary
MyDict.Add('1',Sl);
//add another stringlist on the fly
MyDict.Add('2',TStringList.Create);
//get an instance to the created TStringList
//and fill some data
MyDict.Items['2'].Add('Line 1');
MyDict.Items['2'].Add('Line 2');
MyDict.Items['2'].Add('Line 3');
//finally show the stored data
Writeln(MyDict.Items['1'].Text);
Writeln(MyDict.Items['2'].Text);
finally
//only must free the dictionary and don't need to worry for free the TStringList assignated to the dictionary
MyDict.Free;
end;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
Readln;
end.
Check this link Generics Collections TDictionary (Delphi) for a complete sample about how to use a TDictionary
(remember the only difference with the TObjectDictionary is the Ownership of the keys and/or values that is specified in the constructor, So the same concepts applies to both)
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