Record’s variant

A record can have one or more variant elements or fields. This variant allows data to accessed using one or more different fields. To declare a record contain variant use these statements :

Type

   RecordTypeName = record

      Field_1 : type_1;

      ..

      ..

      Field_n : type_n;

      Case Tag : OrdinalType of

         Constant_1 : ( variant_1);

         Constant_2 : ( variant_2);

      End;

Example record contain variant :

Type

   TCategory = (FullTimer, PartTimer);

   TEmployeeRecord : record

     Name : String(30);

     Case Category : TCategory of

       Full Time : ( Salary : currency;

                              Bonus : currency);

       Part Time : (  Salary : currency);

     End;

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

type
   TCategory = ( FullTimer, PartTimer );
   TEmployeeRecord = record
       Name : String[30];
       Case Category : TCategory of
          FullTimer : ( Salary : currency;
                                  Bonus : currency);
          PartTimer : ( Payment : currency);
   end;

var
   Employee : TEmployeeRecord;

begin
  with Employee do
    begin
     // assigning fields' values
     Name := 'Albert Einstein';
     Category := FullTimer;
     Salary := 1000;
     Bonus := 100;
     // writing fields' values
     writeln('Name : ',Name);
     writeln('Salary : ',Salary:10:2);
     writeln('Bonus : ',Bonus:10:2);
     // assigning fields' values
     Name := 'Albert Einstein';
     Category := PartTimer;
     Payment := 500;
     // writing fields' values
     writeln('Name : ',Name);
     writeln('Payment : ',Payment:10:2);
    end;
  readln;
end.

You can download the complete code here.

Accessing Record’s Elements

After we declare a record ( previous tutorial ), now we are going to access the elements or fields of the record. The fields in a record can be accessed using this notation :

    RecordName.RecordField

Between the field name and the record name separated by a dot.

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

type
   TRecordItem = record
     Item : string;
     Quantity : integer;
     Price : currency;
   end;
var
   ItemStock : TRecordItem;

begin
  // assigning values to record's fields
  ItemStock.Item := 'USB Flash Disk';
  ItemStock.Quantity := 20;
  ItemStock.Price := 10;
  // writing teh fields' values.
  writeln('Item : ',ItemStock.Item);
  writeln('Quantity : ',ItemStock.Quantity,' pc/s');
  writeln('Price : $ ',ItemStock.Price:10:2 );
  readln;
end.

Using with statement

With statement allows us to access a record field without mentioning the record name. The syntax of with statement is :

 with Record do
   begin
     statements
   end;

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
   SysUtils;

type
   TRecordItem = record
     Item : string;
     Quantity : integer;
     Price : currency;
   end;
var
ItemStock : TRecordItem;

begin
  with ItemStock do
    begin
      // assigning values to record's fields
      Item := 'USB Flash Disk';
      Quantity := 20;
      Price := 10;
      // writing teh fields' values.
      writeln('Item : ',Item);
      writeln('Quantity : ',Quantity,' pc/s');
      writeln('Price : $ ',Price:10:2 );
    end;
  readln;
end.

You can download the complete code here.

Record

Record is a structured data type. It contains some elements or fields, and each field can have a different data type. See the picture below.

How to declare a record ?

You have to declare a record after type clause.

type

    RecordTypeName = record

       Field_1 : DataType;

       .

       .

       Field_n : DataType;

    End;

var

   RecordName : RecordTypeName;

For example, we declare a record named ItemStock that has three fields ( Item, Quantity and Price ).

type

   TRecordItem = record

     Item : string;

     Quantity : integer;

     Price : currency;

   end;

var

   ItemStock : TRecordItem;

First, define a TRecordItem then use it to declare a variable named ItemStock. So the ItemStock variable has three fields : Item, Quantity and Price.