iphone - Copying entities in Core Data -


i have couple of core data entities... student , exam.

now, exams 1 object per exam - maths exam 3, english exam 2 etc.

there relationship between students , exams in data model (a student can have several exams). initially, exams floating free, , not attached students.

how make copy of 1 of exams , attach student?

if like:

[student addexamsobject:examobject];

...then think references original exam student, rather making copy.

i need copy because exam has boolean 'hastaken', yes when student has taken exam. if set now, make seem students exam have taken it.

clarification: rather not restructure model. data taken couple of xml files, 1 each students , exams, parsed core data store. instance, exam object might this:

name:maths 5 class-id:12 year-id:4 student-id:0

..with student object looking like

name: dave class-id:12 year=id:4 student-id:222

various rules meant guide exams attached students... instance if exam's ids 0 students take exam. if class-id , year-id match, , student-id 0, exam gets added students same class , year. if student-ids match, student takes exam. etc etc. cannot change way xml outputted server.

another issue exam has too-many relationship question entity... in other words, questions in exam. , have store answers questions each student gives in exam.

edit: wish people try answer question rather tell me restructure whole program. there reasons why data model has been structured is.

edit2: maybe have restructure....

exam shouldn't have hastaken property. think in real world. exam not know has taken because many people have taken it. instance of taking exam, then, should first-class concept in model.

consider this:

exam has many takenexams, takenexams belongs student http://yuml.me/6627495d

now concept of taking exam real object, can model assocation metadata well, such datetaken, score, , on.

also remember core data expects have of inverse associations set well.


Comments

Post a Comment

Popular posts from this blog

asp.net - repeatedly call AddImageUrl(url) to assemble pdf document -

i'm using abcpdf , i'm curious if can recursively call addimageurl() function assemble pdf document compile multiple urls? something like: int pagecount = 0; int theid = thedoc.addimageurl("http://stackoverflow.com/search?q=abcpdf+footer+page+x+out+of+", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetochain(theid); } pagecount = thedoc.pagecount; console.writeline("1 document page count:" + pagecount); //flatten document (int = 1; <= pagecount; i++) { thedoc.pagenumber = i; thedoc.flatten(); } //now try again theid = thedoc.addimageurl("http://stackoverflow.com/questions/1980890/pdf-report-generation", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetoc...
Read more

java - Android recognize cell phone with keyboard or not? -

in android app, want detect user's device if device has keyboard(like motorola milestone) , show corresponding user interface. guys know how that? ! regards justicepenny http://developer.android.com/reference/android/content/res/configuration.html public int keyboard the kind of keyboard attached device. 1 of: keyboard_nokeys, keyboard_qwerty, keyboard_12key. that's it!
Read more

iphone - How would you achieve a LED Scrolling effect? -

how achieve led scrolling effect example below? led sign - led ticker emulator iphone , ipad http://img.skitch.com/20101201-rsfh4p1bajb1wp94k466pdpiuj.preview.jpg sometimes remunerates comment in other posts :) have put code you, should implement font '8pin matrix' realistic feeling. uilabel *label; - (void)viewdidload { [super viewdidload]; label = [[uilabel alloc]initwithframe:cgrectmake(10, 50, 300, 20)]; label.font = [uifont fontwithname:@"courier-bold" size:16.0]; label.backgroundcolor = [uicolor blackcolor]; label.textcolor = [uicolor greencolor]; label.linebreakmode = uilinebreakmodecharacterwrap; // otherwise "…" label.text = @"this led text scrolled "; // blanks space between [self.view addsubview:label]; [nstimer scheduledtimerwithtimeinterval:0.12f target:self selector:@selector(scrolllabel) use...
Read more