List - Delphi - Do I have to release all the elements in TOBJECT before release?

Please about this code:

type
 TClient = class(TObject)
 public 
 Host: String;
 Queue: TIdThreadSafeStringList;
 end;

var
 Clients: TThreadList;

procedure TMain. FormCreate(Sender: TObject);
const
 Hosts: Array[0..4] of String = (
'HOST1','HOST2','HOST3','HOST4,'HOST5 '
 );
var
 I: Integer;
 List: TList;
 Client: TClient;
begin
 Clients := TThreadList. Create;
 Clients.Duplicates := dupAccept;
 for I := Low(Hosts) to High(Hosts) do
 begin
 Client := TClient.Create;
 Client.Host := Hosts[I];
 Client.Queue := TIdThreadSafeStringList.Create;
 Clients.Add(Client);
 Client := nil;
 end; 
end;

I want to know the correct way to release memory:

procedure TMain.FormDestroy(Sender: TObject);
var
 I: Integer;
 List: TList;
begin
 List := Clients.LockLi st;
 try
 for I := 0 to List.Count-1 do
 TClient(List[I]).Free;
 finally
 Clients.UnlockList; 
 Clients.Free;
 end;
end;

Or like this:

procedure TMain.FormDestroy( Sender: TObject);
var
 I: Integer;
 List: TList;
begin
 List := Clients.LockList;
 try
 for I := 0 to List.Count-1 do
 begin
 TClient(List[I]).Queue.Free;
 TClient(List[I]).Free;
 end;
 finally
 Clients.UnlockList;
 Clients.Free;
 end;
end;

In other words, I want I know when I release an object (TClient), do I automatically release all elements (queue), or I have to do it manually.

Thank you!

When the client object is destroyed, the queue object needs to be destroyed. However, the correct way is to let the client The end class is responsible for its members.

type
 TClient = class
 private
 FHost: String;
 FQueue: TIdThreadSafeStringList;
 public
 constructor Create(const Host: string);
 destructor Destroy; override;
 end;
....
constructor TClient. Create(const Host: string);
begin
 inherited Create;
 FQueue := TIdThreadSafeStringList.Create;
 FHost := Host;
end;
 
destructor TClient.Destroy;
begin
 FQueue.Free;
 inherited;
end;

If you do, then it’s impossible Instantiate a class and cannot instantiate its members. Do it in your own way. Every time you need to instantiate the class, you must repeat the code to instantiate the members. It is easy to make mistakes in this way. More importantly, it makes the code more difficult Read and maintain.

Please about this code:

type
 TClient = class (TObject)
 public
 Host: String;
 Queue: TIdThreadSafeStringList;
 end;

var
 Clients: TThreadList;

procedure TMain.FormCreate(Sender: TObject);
const
 Hosts: Array[0..4] of String = (
'HOST1','HOST2','HOST3','HOST4,'HOST5'
 );
var
 I: Integer;
 List: TList;
 Client: TClient;
begin
 Clients := TThreadList.Create;
 Clients.Duplicates := dupAccept;
 for I := Low(Hosts) to High(Hosts) do
 begin
 Client := TClient.Create;
 Client.Host := Hosts[I];
 Client.Queue := TIdThreadSafeStringList.Create;
 Clients.Add(Client);
 Client := nil;
 end;
 end;

I want to know the correct way to release memory:

procedure TMain.FormDestroy(Sender: TObject);
var
 I: Integer;
 List: TList;
begin
 List := Clients.LockList;
 try
 for I := 0 to List.Count-1 do
 TClient(List[I]).Free;
 finally
 Clients.UnlockList;
 Clients.Free;
 end;
end; Or like this:
 
 procedure TMain.FormDestroy(Sender: TObject);
var
 I: Int eger;
 List: TList;
begin
 List := Clients.LockList;
 try
 for I := 0 to List.Count-1 do
 begin
 TClient(List[I]).Queue.Free;
 TClient(List[I]).Free;
 end;
 finally
 Clients.UnlockList ;
 Clients.Free;
 end;
end;
In other words, I want to know that when I release an object (TClient), it automatically releases all elements (Queue), it must be executed manually.
Thank you! 

When the client object is destroyed, the queue object needs to be destroyed. However, the correct way is to let the client class be responsible for its members. 

type
 TClient = class
 private
 FHost: String;
 FQueue: TIdThreadSafeStringList;
 public
 constructor Create(const Host: string);
 destructor Destroy; override;
 end;
....
constructor TClient.Create(const Host: string);
 begin
 inherited Create;
 FQueue := TIdThreadSafeStringList.Create;
 FHost := Host;
end;

destructor TClient.Destroy;
begin
 FQueue.Free;
 inherited;
end;
If you do this, then it is impossible to instantiate the class and its members cannot be instantiated. Follow yourself Every time you need to instantiate a class, you must repeat the code to instantiate members. It is easy to make mistakes in this way. More importantly, it makes the code more difficult to read and maintain.

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