Delphi Basics : Finally command

DelphiBasics

Finally
Keyword

Starts the unconditional code section of a Try statement

keyword Finally(Try
Statement
{Statement...}
Finally
Statement
{Statement...}
End;

Description

The Finally keyword is used to mark the start of the final block of statements in a Try statement. They are executed regardless of what happens in the Try statements.

However, the Finally clause does not actually handle any exceptions - the program will terminate if no Except clause is found (see notes below).

Try-Finally is normally used by a routine to allow cleanup processing to take place, such as freeing resources, with the exception being correctly passed to the caller to handle.

Notes

There are times when you want a construct like this :

Try
  ...
Except
  ...
Finally
  ...
End;

where exceptions are trapped and acted upon, but in all cases, a set of clean up statements are executed. This can be achieved with nested Try statements :

Try
  Try
    ...
  Except
    ...
  End;
Finally
  ...
End;

Related commands

Except		Starts the error trapping clause of a Try statement
On		Defines exception handling in a Try Except clause
Raise		Raise an exception
Try		Starts code that has error trapping

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Example code : Zero divide with a finally clause

var
  number, zero : Integer;
begin
  // Try to divide an integer by zero - to raise an exception
  number := -1;
  Try
    zero   := 0;
    number := 1 div zero;
    ShowMessage('number / zero = '+IntToStr(number));
  Finally
    if number = -1 then
    begin
      ShowMessage('Number was not assigned a value - using default');
      number := 0;
    end;
  end;
end;

Show full unit code

  Number was not assigned a value - using default

  Then, the program terminates with an EDivByZero error message - the finally clause did not trap the error.