Delphi Basics : Var command

DelphiBasics

Var
Keyword

Starts the definition of a section of data variables

1	keyword Var(Var Name1 : Type; {...}
2	Var Name1 : Type = Expression1; {...}
3	Name (Var Var1 : type {;...});

Description

The Var keyword is used to start a section of variable definitions.

The section is terminated by the next keyword in a program.

Within the section, one or more variables may be defined. These can be of any data type.

1.Variables with no initial value

These are defined with a given type, such as string or Integer but with no assigned default initial value.

2.Variables with an initial value

These are defined with a given type, such as string or Integer with an assigned initial value. Only global variables may be initialised.

3.Variable routine parameters

When passing data to a routine (function or procedure), you can prefix the parameter definition with Var if the variable itself is to be updated by the routine. This allows a caller to pass data to a routine that will be enriched by the routine.

Related commands

Const		Starts the definition of fixed data values
Function		Defines a subroutine that returns a value
Out		Identifies a routine parameter for output only
Procedure		Defines a subroutine that does not return a value
Type		Defines a new category of variable or process

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Example code : Defining local and parameter variables

Var  // Local variables
  apples, bananas : Integer;
begin
  // Initialise our fruit counts
  apples  := 1;
  bananas := 1;

  // Show their initial values
  ShowMessage('Apples  = '+IntToStr(apples));
  ShowMessage('Bananas = '+IntToStr(bananas));
  ShowMessage('');

  // Increment them in the UpdateCounts routine
  UpdateCounts(apples, bananas);

  // Show their new values - only Bananas will be updated
  ShowMessage('Apples  = '+IntToStr(apples));
  ShowMessage('Bananas = '+IntToStr(bananas));
end;

// A procedure to increment the passed parameter values
procedure TForm1.UpdateCounts(count1: Integer; Var count2: Integer);
begin
  // Increment both passed parameter values
  Inc(count1);
  Inc(count2);
end;

Show full unit code

  Apples = 1
  Bananas = 1

  Apples = 1
  Bananas = 2