Records are a structured type consisting of collections of objects of other types. A record variable can be used
as a whole, or its
individual components, called fields, can be used individually.
The syntax for a record declaration is shown here:
RecType = record
<field1>: <sometype>;
<field2>: <sometype>;
.
.
.
<fieldn>: <someType>;
end;
Once a variable of a record type has been declared, you can assign information to one of its fields by writing
the name of the variable, a period, and then the field name. In general, a field of a record can be used wherever
a variable of the field's type would be acceptable. For example:
type
student = record
name: string[40];
age: integer;
GPA: real;
major: ( music, english, history, science );
end;
var S
: student;
begin
S.name := "Susan Carlson";
S.age := 19;
S.GPA := 3.41;
S.major := english;
end.
The WITH statement is a shorthand notation for accessing the fields of a record; inside a WITH statement
(which may include a begin/end block), the name of the record is unnecessary to access its fields. For example,
the previous assignments to record variable S could have been written as:
begin
with S do
begin
name := 'Susan Carlson';
age := 19;
GPA := 3.41;
major := english;
end;
end.
Variant Records
A variant record is a special form of record in which some or all of the fields are given overlapping storage in
memory. This allows an application to conserve memory when many of a record's fields are inappropriate for a particular
class of object being stored.
For example, a record that represents a transaction in a department store can have separate fields according to
the method of purchase; one for cheques, and another for credit cards.
type
paymentType = ( cash, cheque, credit );
purchase = record
Amount : currency;
Date : string[8];
case payMethod : paymentType of
cash : ( );
cheque : (chequeNo : integer; licenseNumber: longint );
credit: (cardNo : longint; expiration: string[8]);
end;
The variant part of the record definition must come at the end.
program
RecordExample;
type
cheque = record
number: integer;
amount: currency;
date: array [1..8] of char; { '99/99/99' }
payee: string[40];
end;
var
MyCheque : cheque;
YourCheque: cheque;
begin
MyCheque.number := 753; { Christmas present }
MyCheque.amount := 87000000.00;
MyCheque.date := '12/25/88';
MyCheque.payee := 'Myself';
YourCheque := MyCheque; { all fields assigned
automatically }
YourCheque.number := YourCheque.number + 1;
with
YourCheque do
begin
Writeln('Amount = ',amount);
Writeln('Date = ',date);
end;
end. { RecordExample }
