CODEWITHSUNDEEP
delphi
zeus
zeus

Reputation: 12965

How to pass a Var parameter to a Thread

I have thoses objects :

TmyObject1=class
public 
  Status: integer;
end;

TmyObject2=class
public 
  StatusA: integer;
  StatusB: integer;
end;

I have many objects like those one with many status fields declared. I would like to call a function and let the function update the value of one of the status field. quite easy I declare the function like this :

function MyFunction(var AStatus: Integer);

and I call it like this

MyFunction(myObject1.Status);

or for example

MyFunction(myObject2.StatusB);

that good but now my problem arrive, in MyFunction I create a thread and I want to let the possibility to the thread to update also the value of Status. something like this :

function MyFunction(var AStatus: Integer);
begin
  MyTread.??ObjectStatus?? := AStatus;
  MyTread.start; 
end;

procedure TmyThread.execute;
begin
  ...
  ??ObjectStatus?? := NewStatus
  ...
end;

How can I do ? what type must be the TmyThread.??ObjectStatus??. I was thinking to gave to MyTread a pointer address but I m afraid that if memory relocation between the start and the end of the thread that the pointer address could become wrong (Code must work on ios/android/windows/etc.). any other options to solve my problem ?

Upvotes: 0

Views: 444

Answers (1)

Uwe Raabe
Uwe Raabe

Reputation: 47819

Instead of a var parameter you can provide getter and setter to your function:

function MyFunction(GetStatus: TFunc<Integer>; SetStatus: TProc<Integer>);
begin
  MyThread.GetStatus := GetStatus;
  MyThread.SetStatus := SetStatus;
  MyThread.start; 
end;

procedure TmyThread.execute;
begin
  ...
  OldStatus := GetStatus;
  SetStaus(NewStatus);
  ...
end;

Calling this function requires some anonymous methods now:

MyFunction(
  function: Integer
  begin
    result := myObject1.Status;
  end,
  procedure(Arg: Integer)
  begin
    myObject1.Status := Arg
  end);

Of course you have to make sure that myObject1 is available during the thread execution.

Upvotes: 2

Related Questions