Hi Gerry,
No, you don't need to do that. You don't need to declare a new pointer for to point out those components. As i said before, when you are working with Delphi objects, you want or not, you are using pointers. Delphi is hiding the implementation details from the programmers so you don't need to know that you are working with pointers.
For example :
Unit1 (Main unit)
- has a form named Form1 - there is an edit control on it Edit1
Unit2
- Unit1 is into your uses clause
Now when you want to access to the Edit1 component from the Unit2, you just need to type :
Form1.Edit1.Text := 'I call from the Unit2';
When you want to call the ProgressBar1 from the Unit1, you should add the Main, to your uses clause and call directly :
MainForm1.ProgressBar1.Position := CalculatedBarPosition.
Pointers are not using like this. When you create an object variable, you can point out an another same typed object. For example, you can do something like this into the Unit1 :
var MyProgress := TProgressBar; ..
for i := 0 to MainForm1.ComponentCount - 1 do
begin
if (MainForm1.Components[i] is TProgressBar) then // is this a progress bar ?
begin
MyProgress := TProgressBar(MainForm1.Components[i]); // now your local variable points out the MainForm1's one of the progress bar
MyProgress.Position := CalculatedBarPosition; // now you use like it's a local
end;
end;
Above example looks like MyProgress copied all the data includes by MainForm1.ProgressBarX, but it's not. This is what i mentioned before. Now your MyProgress knows the address of MainForm1's ProgressBarX, so, now you can do whatever you want with this address.
Lets wonder that you have a beautiful house near the beach. One day when you are talking with one of your best friend, you wanted to talk about your beatiful house which is near the sea. You said tons of great things about it and finally he said that he wants to visit your home so he wants to know where is it. What is the best way ? Would you bring the home near him ? or Would you give him its address ? of course you would give the address :)) This is where we need to use pointers.
Final word is, you don't need to create a pointer for to reference to the components.
HTH,
Oktay Sancak
Gerry Bendixen wrote:
Obviously I was not so clear on my goals. Here's an attempt to provide an example, stripped of all non-essential details. Hopefully I present it correctly. I have a 'main' unit (Main.pas) with a form. On the form is ProgressBar1 (a TProgressBar component) I have a 'uses' unit (Unit1.pas) that does processing and the goal is to show the progress of this processing by updating the ProgressBar on the main form.
(1) Type PProgressBar = ^TProgressBar ; //Declare pointer type (2) Var ProgressBar1Ptr : PProgressBar ; //Declare pointer variable (3) ProgressBar1Ptr := PProgressBar(ProgressBar1) ; //Assign value to pointer (4) TProgressBar(ProgressBarPtr).Position := CalculatedBarPosition ;
Line 1 and 2 are visible to both Main and Unit1. Line 3 is executed in Main to set the value to the pointer. Line 4 is executed in Unit1 is update the position of the progress bar.
Again, thanks in advance for your attention and any hints, Gerry B.
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