How to run procedure from another unit?

Question

Well this kind of n00b question but I still can't figure it out. I have unit main with procedure Discard() in it. Now I have another unit engine and I want to run from it procedure Discard() of unit main. I have main in uses section of engine.pas. I tried to call procedure with main.Discard() but no good. What am I doing wrong?

Solution 1

You need to put the procedure's signature in your interface, like so:

unit main;

interface

procedure Discard();

implementation

procedure Discard();
begin
//do whatever
end;

Other units can only "see" whatever's listed in the interface section.

Solution 2

In unit "Main" you declare Discard in the "interface" section:

unit Main;

interface

uses ...

procedure Discard (...); // only the declaration, not the entire procedure

implementation

... // code

Now in unit "Engine" you add "Main" to the "uses" section.

uses Main, ...

Thats it, you can call Discard(...) now. If there are more than one Discard() you can explicitely call this Discard() by using Main.Discard().