----- Original Message ----- From: "Alan Colburn" <[EMAIL PROTECTED]> To: "Borland's Delphi Discussion List" <[email protected]> Sent: Monday, April 24, 2006 10:01 AM Subject: Re: Delphi and Java
> Thanks for the response, Kevin. It was amazingly apt, for me, because it's > *exactly* the point I was reading about last night :-) In fact, your next > post, about TObjList is apt, too, because (continuing the same example), > students don't register for single courses & courses aren't assigned single > students. Here's what I'm wondering at this point ... > > So Student has a field Course of type TCourse, and the Register procedure > associates a TCourse object with Student--I got that. I also understand the > need to create an empty TCourse object in the TStudent constructor. I'm > assuming that Student.Register (CourseName:String) would need to > (a) find a TCourse object whose CourseName field matches the one from the > signature with Student, No, you just assign a CourseName or CourseNameIndex which will point to a list of possible courses; > *have Student's Course field point to this TCourse instead of the blank one > created in the constructor,* AND This should not be necessary; > (b) the same TCourse object would need to associate Student with itself (add > Student to a TObjList?)... Nor this! If you want a list of students associated with each course, you can construct it at run time by running through all students one by one to see if they have a coursename corresponding to the course you are concerned with; If you construct a Student->Course structure and a Course->Student structure, it will be hard to keep both alligned: it is best to construct one only and derive a reverse relationship list only as needed from it; You need two 'course' object structures todefine the variables required: tCourseAvailable and tCourseAssigned; the tCourseAssigned object only need a variable that indicates which tCourseAvailable instance it 'points' to (either an index number or a string name: you could include the student name, though this is already implicit in the Tstudent object that 'owns' the assigned course instance): the tCourseAssigned object is already part of a tstudent object so no association is necessary (you need a studentname variable as part of the tstudent object: any tcourse objects are implicitly associated with this student name!!) I think you need an objectlist of all courses available which will have the parameters that you want to associate with each student (); You could create a 'Faculty_list' object which contains a 'courses_available_list' object, which contains a list of tCourseAvailable objects: You can pass the coursename value to the student object which will add a courseobject for that student, and which by definition is associated with that particular student (if you have multiple students, you can create a studentobjectlist component which contains lists of student objects, each having its own internal list of assigned courses) College>FacultyList->Faculty->CoursesAvailableList->CourseAvailable StudentList->Student->CourseAssignedList->CourseAssigned Are you using a database to store the data: if so you can use a dataset from the database to read in data to your Student object and to save new or altered student data; You can read in data using the usual Master-Detail relationships from the relevant database tables, the structure of which would resemble the object stuctures that we have already defined in OO terms; The types of structures that I am currently developing are very similar, except they also have methods for writing and reading the data to an associated database (Object Oriented Database): its a bit advanced if you are only learning, and database programming knowledge is required (SQL language etc.); _______________________________________________ Delphi mailing list -> [email protected] http://www.elists.org/mailman/listinfo/delphi
