Learn Pascal in a Three Days (2nd Ed.)
(Publisher: Wordware Publishing, Inc.)
Author(s):
ISBN: 1556225679
Publication Date: 07/01/97

8-5 Nesting Records

In the “EmployeeRecord” example you may split the field address information to street address, city, state, and zip code. This means that the address field becomes a record nested in the “EmployeeRecord.” The new record will look as follows:

    TYPE
     AddressRecord = RECORD
                     Street           :STRING[18];
                     City     :STRING[15];
                     State            :STRING[2];
                     Zip      :String[5];
            END;
     EmployeeRecord = RECORD
                     Name             :STRING[25];
                     AddressRec       :AddressRecord;
                     Phone            :STRING[12];
                     Rate             :REAL;
                     MaritalStatus    :CHAR;
                    END;
    VAR
     EmployeeRec :EmployeeRecord;

In this declaration, you have two record types: “AddressRecord” and “EmployeeRecord.” The field “AddressRec” in the employee record is of the type “AddressRecord” which was defined before. To deal with any fielded variables in the “AddressRec” you have to attach both names of the two records “EmployeeRec” (which is the grandparent) and “AddressRec” (which is the parent). Here are some sample assignments:

    EmployeeRec.AddressRec.Street:= '15 Darell Street';
    EmployeeRec.AddressRec.Zip:= '60108';

When you display any of these fields you use the same method:

    WRITELN(EmployeeRec.AddressRec.Street);
    WRITELN(EmployeeRec.AddressRec.City);

Here is the complete program:

{ -------------------------- figure 8-4 -------------------------- }
PROGRAM NestedRecord(OUTPUT);
TYPE
 AddressRecord = RECORD
            Street  :STRING[18];
            City            :STRING[15];
            State   :STRING[2];
            Zip             :String[5];
           END;
 EmployeeRecord = RECORD
            Name                       :STRING[25];
            AddressRec                 :AddressRecord;
            Phone                      :STRING[12];
            Rate                       :REAL;
            MaritalStatus   :CHAR;
               END;
VAR
 EmployeeRec   :EmployeeRecord;
BEGIN
 EmployeeRec.Name:= 'Jean L. Krauss';
 EmployeeRec.AddressRec.Street:= '15 Darell Street';
 EmployeeRec.AddressRec.City:= 'Bloomingdale';
 EmployeeRec.AddressRec.State:= 'IL';
 EmployeeRec.AddressRec.Zip:= '60108';
 EmployeeRec.Phone:= '312-987-5432';
 EmployeeRec.Rate:= 27.5;
 EmployeeRec.MaritalStatus:= 'M';
 WRITELN('Employee Name:  ', EmployeeRec.Name);
 WRITELN('Address:   ', EmployeeRec.AddressRec.Street);
 WRITELN('         ', EmployeeRec.AddressRec.City);
 WRITE('         ', EmployeeRec.AddressRec.State);
 WRITELN(' ', EmployeeRec.AddressRec.Zip);
 WRITELN('Telephone #:    ', EmployeeRec.Phone);
 WRITELN('Hourly Rate:   $', EmployeeRec.Rate:0:2);
 WRITELN('Marital Status: ', EmployeeRec.MaritalStatus)
END.

The output is:

Employee Name:  Jean L. Krauss
Address:    15 Darell Street
          Bloomingdale
          IL 60108
Telephone #:     312-987-5432
Hourly Rate:    $27.50
Marital Status: M

If you would like to use the WITH statement with such a nested record you need two nested WITH blocks, thus:

    WITH EmployeeRec DO
     WITH AddressRec DO
           BEGIN
            Name:= 'Tammy M. Ockman';
            Street:= '344 Temple Dr.';
            ...
      END;

If any field identifier belongs to the “AddressRec,” it will be modified by both “AddressRec” and “EmployeeRec,” but if it belongs to the “EmployeeRec” directly, it will be modified by “EmployeeRec” only. If it is a regular variable, it will not be modified at all.

Summary

In this chapter you have met two structured data types, the set and the record, and are now familiar with their features.

1.  You now know how to declare a set of a specific base type using the form:

    type-identifier = SET OF base-type;

2.  You also know the standard set operators (union (+), intersection (*), and difference (-)) and the set relational operators ( = >= <= <>), and learned how to use these operators to process sets.

3.  You are familiar with restrictions on sets, as well as their main uses in programming.

4.  You declare record types using the form

    RECORD
     filed-list
    END;

5.  You can access fields using either fielded variables or the WITH statement, which takes the form:

    WITH record-identifier DO
     statement;

6.  You also know how to declare and use nested records and how to process them as well.