UQI107S3

1. UQI107S3 Object Orientation lecture 2

2. Plan • Review Tutorial 1 • Testing • Mayday development • latlong type, boat type, boats table • procedures • 3 Tier application • Some distinctions

3. Review tutorial 1 • Using SQLPLUS -See notes • Latitude and Longitude, Degrees and minutes • Variables and values - see later • Additions to tests - • asString() not tested • should be able to predict answer to test

4. new method -asDegrees() • Add to definition of dm type member function asDegrees return real, • Add to body member function asDegrees return real is begin return degrees + sign(degrees) * minutes/60; end; • Compile sqlplus user/password < dm.sql • Test it select dm(0,30).asDegrees() from dual;

5. Review Tutorial - constructors • Test scripts use the constructor to create an object of the new type: • dm(30,45) • creates an object of type dm with • degrees = 30 • minutes = 45 • same thing happens when you enter a date - ‘04/02/03’ in a date field - a date value is constructed

6. Testing • Develop - test • develop small units, bottom-up • develop test scripts so that tests can be repeated whenever a change is made - ‘regression testing’ • select dm(30,30).asMin() from dual; • Predict output before running test • value should be 30*60 + 30 = 1860 • select dm(30,30).asMin()- 1830 from dual; • output should be 0 • Testing strategy part of ‘Extreme Programming’ and ‘Agile Development’

7. Mayday development • Define base degrees/minutes type • test • Define two further types - latlong and boat • test • Define table of boat types - to store objects • Define some boats • test • Create PL/SQL procedures to access data from a browser • test

8. Define the ‘Interface’ to the type: it supplies all information a user of this type needs to know create or replace type latLong as object ( latitude dm, longitude dm, member function distanceTo(x latLong) return real , member function asString return varchar ); Values of these variables will be objects of type dm parameter

9. Values and variables • Base types - in the type dm: • degrees is a variable of type number • 30 is a value of type number • Defined types • latitude is a variable of type dm • dm(30,0) is a value (an object) of type dm

10. Now define the ‘Implementation’ of each function - the code that makes it produce the result: create or replace type body latLong as member function distanceTo(x latLong) return real is dlat real; dlong real; -- this is an approximation for short distances begin dlat:= latitude.asMin()- x.latitude.asMin(); dlong:=longitude.asMin() - x.longitude.asMin(); dlong:=dlong*cos((latitude.asRad()+x.latitude.asRad())/2); return round(sqrt((dlat*dlat) + (dlong*dlong))); end; call the asMin() function on the object in variable ‘latitude’ Local variables Return computed distance This calculation is a bit tricky, so good to put it in one place, test it and then simply use it:

11. member function asString return varchar is hemi char(2); pole char(2); begin if (latitude.degrees < 0) then pole:='S '; else pole:='N '; end if; if (longitude.degrees < 0) then hemi:='E '; else hemi:='W '; end if; return pole || latitude.abs().asString() || ' ' || hemi || longitude.abs().asString(); end;

12. Construct dm object Construct dm object select latlong(dm(20,0), dm(30,0)).asString() from dual; All these objects are ‘transient’ - exist for the calculation only Construct latlong object

13. Test latlong.distanceTo(latlong) Receiving Object Surprisingly, can have blanks here! select latlong(dm(0,0), dm(0,0)) .distanceTo( latlong(dm(1,0), dm(0,0)) ) from dual; Function call Object as Parameter Result should be 60

14. Creating persistent Objects Define create or replace type boat as object ( name varchar(20) ,pos latlong ); Test select boat('Perdika', latlong(dm(53,20), dm (2,48))) from dual; Create table create table boats of boat; Create some persistent objects insert into boats values('Perdika',latlong(dm(20,30),dm(10,20))); insert into boats values('Flash',latlong(dm(21,35),dm(12,20)));

15. UML Class Model Using Rational Rose

16. 3-tier system User interface using Browser Requests + data HTML Business rules using P|L/SQL SQL Relation (accessed by cursor) Relational Database using Oracle 9

17. The procedure to make a form to select a boat and range create or replace procedure chooseboat is cursor allboats is select * from boats b; begin htp.print('<form action=getnearestboats method=get>'); htp.print('<br>Target boat name <select name=reqname>'); for b in allboats loop htp.print('<option>' || b.name || ' </option> ' ); end loop; htp.print('</select>'); htp.print('Range to search <input type=text name=reqrange size=5 value=100>'); htp.print('<input type=submit value=‘search’>'); htp.print('</form>'); end; SQL statement html

18. Procedure to find boats in range create or replace procedure getnearestboats (reqname varchar, reqrange varchar) is target boat; cursor selboats is select * from boats b where b.name !=target.name -- dont want target and b.pos.distanceTo(target.pos) < reqrange order by b.pos.distanceTo(target.pos); begin select value(b) into target from boats b where name=reqname; …..

19. Generating the output htp.print('<h3>'|| target.name || ' at position ' || target.pos.asString() || '</h3>'); htp.print('<h4>Boats within ' || reqrange || ' miles</h4>'); htp.print('<ul>'); for b in selboats loop htp.print('<li><b>' || b.name || '</b> at ' || b.pos.asString() || ' is ' || b.pos.distanceTo(target.pos) || ' miles away</li>'); end loop; htp.print('</ul>'); end;

20. Distinctions -1 • Type and Object • type defines the structure and behaviour of all the objects of that kinds • object is a single instance of that type • compare with: • Base type String and ‘String’ • Table EMP and tuple (3456,’Smith’,’Accounting’)

21. Distinctions - 2 • Variable and Value • a value is fixed, a variable is a name for a place to store values • Interface and Implementation • interface defines what a user of an object can do, implementation defines how it works internally

22. Distinctions - 3 • Transient and Persistent • Transient objects exist only while a program is executing • Persistent objects are stored in permanent storage (e.g. a Database) and are deleted on command

23. Next week • Tutorial • install this application and make small changes to the procedures • Lecture • Inheritance • UML diagrams