A language feature worth understanding

15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.

Use the language note below to explain this example’s state changes. Identify what is copied, what is shared, what can fail, and what is released. Only some of those questions apply to this particular program: say which ones. Make one deliberate change, predict the effect, and compare it with the actual result. A familiar-looking operator in another language may obey a different rule.

Object Pascal classes and Objective-Pascal are distinct. First learn class, construction, and Free using the Linux lab. Objective-Pascal adds Objective-C interoperability through mode switches; this lab does not provide that Apple runtime.

program AgilaStudy;
{$mode objfpc}{$H+}{$assertions on}

type TPlan = class
  public Done: Integer;
end;
var Plan: TPlan;
begin
  Plan := TPlan.Create;
  try
    Plan.Done := 3;
    writeln(Plan.Done);
  finally
    Plan.Free;
  end;
end.

Expected result: 3

Practice and evidence

Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.

Language reference