A primary question of Delete in Delphi!

baishui4

I just started to learn DELPHI, and I don’t understand many questions, and I can’t solve them after all. Ask the big brothers and sisters? Ha...

I dragged several controls in Delphi. Then, in a BUTTON click event, I wrote the following:
　　Begin
        Label1.Caption:=Concat(Edit1.text,Edit2.text);
        Label2.Caption:=Delete(Label1.Caption,1,1);
　　End;
Celsius, prompt:
[Error] Unit1.pas(34): Constant object cannot be passed as var parameter
I then changed it to:
var
        S:string;
begin
        Label1.Caption:=Concat(Edit1.text,Edit2.text);
        S:=label1.Caption;
        Label2.Caption:=Delete(S,1,1);
end;
The result is:
[Error] Unit1.pas(35): Incompatible types:'String' and'procedure, untyped pointer or untyped parameter'

Dare to ask everyone, what does this mean?

vesevese

Changed to:
var
        S:string;
begin
        Label1.Caption:=Concat(Edit1.text,Edit2.text);
        S:=label1.Caption;
        //Label2.Caption:=Delete(S,1,1);
        Delete(S, 1, 1);
        Label2.Caption := S;
end;
Explanation: The first error occurred because the first parameter of the Delete function was of variable type, that is, reference type.
      The second error is because the Delete function has no return value, which is a procedure of type Procedure

baishui4

Thank you, big brother upstairs, the problem is solved, thank you so much!