Delphi Basics : Then command

DelphiBasics

Then
Keyword

Part of an if statement - starts the true clause

1	keyword Then(if Condition then Statement;
2	if Condition then Statement else Statement;

Description

The Then keyword is part of the If statement. It is used to start the section of code executed when the if condition is true.

There are two forms of the If statement - one with an else clause, the other not.

If works as follows :

If the condition is true, then the first statement is executed. If false, then this statement is bypassed. If there is an else statement, it is executed instead.

In all cases, the Statement clause must be contained in a begin/end block if it is longer than one statement in length.

Notes

It is an easy mistake to make, but Delphi insists on no ; after the then statement if an else statement follows.

Related commands

Else		Starts false section of if, case and try statements
End		Keyword that terminates statement blocks
If		Starts a conditional expression to determine what to do next

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Example code : Illustrate various uses of the then clause

begin
  // Illustrate a simple if statement that executes true
  if True Then ShowMessage('True!');

  // Illustrate the same, but with multiple actions
  if 1 = 1 Then
  begin
    ShowMessage('We now have');
    ShowMessage('multiple lines');
  end;

  // Illustrate a simple if statement that fails
  if 1 = 2 Then ShowMessage('1 = 2');

  // Illustrate an if then else statement
  // Note the lack of a ';' after the 'then' clause
  if False
  Then ShowMessage('True')
  else ShowMessage('False');

  // Nested if statements - Delphi sensibly manages associations
  if true Then
    if false Then
      ShowMessage('Inner then satisfied')
    else
      ShowMessage('Inner else satisfied')
  else
    ShowMessage('Outer else satisfied')
end;

Show full unit code

  True!
  We now have
  multiple lines
  False
  Inner else satisfied