How can I change this code so that it doesn't infringe MVC principles? - objective-c

Question

I am making a quiz app for chemistry reactions. The app gives the user a question, and the user types in the reactants and products in two separate textfields.
I have a data class, which contains all the possible quiz questions. Then, based on specific parameters, the data class selects a certain amount of questions from the pool of possible questions and shuffles them into an array, quizQuestions.
I also have a view controller, quizController. For each question, a new instance of quizController is loaded. The vc needs the data to know which question to display, what the correct answer is, etc.
This is my original solution to communicate between the data and the vc's.
I create an instance of the data class, data.
I create vc1 for the first question, and set data as a property of vc1, and set its tag as 1, so that it loads the 1st question from the data.
After the user answers the first question, I create a new view controller, vc2, in a method of vc1, make the tag 1 more than the last vc's so that the second question loads, and pass data from vc1's property to vc2's.
And then I repeat for the other questions.
However, this is not very good design, and I am looking for a better solution. I don't think I can use a class method because the data is supposed to contain a random set of questions. Below I have the code for the data class.
// the data class as it is now, designed for instance methods
- (id)init {
self = [super init];
if (self) {
//Questions of the same type belong to a "ROW" (Reaction of Week)
//individual questions
// Items in array: (1)Question, (2)Reactants, (3)Products, (4)Elements for keyboard
NSArray *R1Q1 = [[NSArray alloc] initWithObjects:#"Methanol is burned completely in air", #"2CH₃OH(l) + 3O₂(g)", #"2CO₂(g) + 4H₂O", #"C,H,O", nil];
NSArray *R1Q2 = [[NSArray alloc] initWithObjects:#"Ammonia is burned in excess oxygen gas", #"4NH₃(g) + 7H₂O(l)", #"4NO₂(g) + 6H₂O(l)", #"N,H,O", nil];
NSArray *R1Q3 = [[NSArray alloc] initWithObjects:#"Hydrogen sulfide gas is burned in excess oxygen gas", #"2H₂S(g) + 3O₂(g)", #"CO₂(g) + 2SO₂(g)", #"H,S,O", nil];
NSArray *R2Q1 = [[NSArray alloc] initWithObjects:#"Solid potassium is added to a flask of oxygen gas", #"K(s) + O₂(g)", #"KO₂(s)", #"K,O", nil];
NSArray *R2Q2 = [[NSArray alloc] initWithObjects:#"Sodium metal is dropped into a flask of pure water", #"2Na(s) + H₂O(l)", #"2Na⁺(aq) + 2OH⁻(aq) + H₂(g)", #"Na,H,O", nil];
NSArray *R2Q3 = [[NSArray alloc] initWithObjects:#"A piece of lithium is heated strongly in oxygen", #"4Li(s) + O₂(g)", #"2Li₂O(s)", #"Li,O", nil];
NSArray *R3Q1 = [[NSArray alloc] initWithObjects:#"Solutions of potassium chloride and silver nitrate are mixed", #"Ag⁺(aq) + Cl⁻(aq)", #"AgCl(s)", #"K,Cl,Ag,N,O", nil];
NSArray *R3Q2 = [[NSArray alloc] initWithObjects:#"Solutions of iron(III) nitrate and sodium hydroxide are mixed", #"Fe³⁺(aq) + 3OH⁻(aq)", #"Fe(OH)₃(s)", #"Fe,N,O,Na,H", nil];
NSArray *R3Q3 = [[NSArray alloc] initWithObjects:#"Solutions of nickel iodide and barium hydroxide are mixed", #"Ni²⁺(aq) + 2OH⁻(aq)", #"Ni(OH)₂(s)", #"Ni,I,Ba,OH", nil];
// add rest
//organize questions into groups
row1 = [[NSArray alloc] initWithObjects:R1Q1, R1Q2, R1Q3, nil];
row2 = [[NSArray alloc] initWithObjects:R2Q1, R2Q2, R2Q3, nil];
row3 = [[NSArray alloc] initWithObjects:R3Q1, R3Q2, R3Q3, nil];
//add rest
// array containing all questions
allRows = [[NSMutableArray alloc] initWithObjects:row1, row2, row3, nil];
//in a real situation, needs to be given to class dynamically
self.maxRowNumber = 3;
self.questionsPerRow = 2;
}
return self;
}
- (void)selectQuestions {
self.quizQuestions = [[NSMutableArray alloc] init];
for (int j = 0; j<self.maxRowNumber; j++) {
//shuffle each row
NSMutableArray *row = [NSMutableArray arrayWithArray:[allRows objectAtIndex:j]];
[row shuffle];
//add questions from each row
for (int k = 0; k<self.questionsPerRow; k++)
[quizQuestions addObject:[row objectAtIndex:k]];
}
[quizQuestions shuffle];
}
View Controller code excerpts
# pragma mark Cell Setup
//1st cell in tableview
- (void) setUpEquationCell: (UITableView *) tableView {
equationCell = (EquationCell *) [tableView dequeueReusableCellWithIdentifier:#"equationCell"];
if (equationCell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"EquationCell" owner:self options:nil];
equationCell = (EquationCell*) [nib objectAtIndex:0];
[equationCell.leftButton addTarget:self action:#selector(addDissociateCell) forControlEvents:UIControlEventTouchUpInside];
[equationCell.rightButton addTarget:self action:#selector(addBalanceCell) forControlEvents:UIControlEventTouchUpInside];
}
}
- (void) setUpBalanceCell: (UITableView *) tableView {
//2nd cell in tableview
balanceCell = (BalanceCell *) [tableView dequeueReusableCellWithIdentifier:#"balanceCell"];
if (balanceCell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"BalanceCell" owner:self options:nil];
balanceCell = (BalanceCell*) [nib objectAtIndex:0];
// stores data from equation cell into model
for (FormulaLabel *label in equationCell.leftView.equationOrder)
[leftData.equation addObject:label.text];
for (FormulaLabel *label in equationCell.rightView.equationOrder)
[rightData.equation addObject:label.text];
[leftData setUpBalancedEquation];
[rightData setUpBalancedEquation];
[self setUpView:balanceCell.leftView fromArray:leftData.equation toArray:leftBalanceItems];
[self setUpView:balanceCell.rightView fromArray:rightData.equation toArray:rightBalanceItems];
[self addBalanceTapMethodInArray:leftBalanceItems Data:leftData];
[self addBalanceTapMethodInArray:rightBalanceItems Data:rightData];
}
}
- (void) setUpDissociateCell: (UITableView *) tableView {
dissCell = (DissociateCell *) [tableView dequeueReusableCellWithIdentifier:#"dissCell"];
if (dissCell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"DissociateCell" owner:self options:nil];
dissCell = (DissociateCell*) [nib objectAtIndex:0];
leftData.disEquation = [[NSMutableArray alloc] init];
rightData.disEquation = [[NSMutableArray alloc] init];
// stores data from equation cell into model
for (FormulaLabel *label in equationCell.leftView.equationOrder)
[leftData.disEquation addObject:label.text];
for (FormulaLabel *label in equationCell.rightView.equationOrder)
[rightData.disEquation addObject:label.text];
[self setUpView:dissCell.leftView fromArray:leftData.disEquation toArray:leftDisItems];
[self setUpView:dissCell.rightView fromArray:rightData.disEquation toArray:rightDisItems];
[self addDissTapToArray:leftDisItems fromData:leftData inView:dissCell.leftView];
[self addDissTapToArray:rightDisItems fromData:rightData inView:dissCell.rightView];
[dissCell.dissociateButton addTarget:self action:#selector(dissociate) forControlEvents:UIControlEventTouchUpInside];
}
[dissCell.rightButton addTarget:self action:#selector(addBalanceCell) forControlEvents:UIControlEventTouchUpInside];
}
- (void)addDissociateCell {
[cellOrder addObject:#"dissociateCell"];
[table reloadData];
NSIndexPath *myIndexPath = [NSIndexPath indexPathForRow:0 inSection:([cellOrder count]-1)];
[table scrollToRowAtIndexPath:myIndexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
}
- (void) addDissTapToArray:(NSMutableArray*)viewOrder fromData:(EquationData*)data inView:(UIView*)view {
NSString *leftOrRight;
if (view == dissCell.leftView)
leftOrRight = #"left";
else
leftOrRight = #"right";
for (int j=0; j < [viewOrder count]; j++) {
if (j%2==0) {
UIView *formulaView = [viewOrder objectAtIndex:j];
//dissociate method
FalseTarget *target = [[FalseTarget alloc] initWithVC:self leftOrRightView:leftOrRight];
UITapGestureRecognizer* tap = [[UITapGestureRecognizer alloc] initWithTarget:target action:#selector(dissTap:)];
[formulaView addGestureRecognizer:tap];
// cancelling method
FalseTarget *target2 = [[FalseTarget alloc] initWithVC:self Data:data ViewList:viewOrder view:view];
UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:target2 action:#selector(dissLongTap:)];
[formulaView addGestureRecognizer:longPress];
}
}
}
- (void)addCompoundToLabel:(UIGestureRecognizer *)recognizer leftOrRight:(NSString*)leftRight{
if( [recognizer state] == UIGestureRecognizerStateEnded ) {
FormulaLabel* label = (FormulaLabel*)[recognizer view];
dissIndex = label.tag;
dissCell.unDissociated.text = label.text;
currentDissCellView = leftRight;
}
}
- (void)dissociate {
EquationData *data;
NSMutableArray *viewOrder;
UIView *view;
if ([currentDissCellView isEqualToString:#"left"]) {
data = leftData;
viewOrder = leftDisItems;
view = dissCell.leftView;
}
else {
data = rightData;
viewOrder = rightDisItems;
view = dissCell.rightView;
}
FormulaLabel *c1 = [dissCell.leftTextField.equationOrder objectAtIndex:0];
FormulaLabel *c2 = [dissCell.rightTextField.equationOrder objectAtIndex:0];
[data updateDisEquationAtIndex:dissIndex withCompound1:c1.text Compound2:c2.text];
for (UIView *view in viewOrder)
[view removeFromSuperview];
[viewOrder removeAllObjects];
[self setUpView:view fromArray:data.disEquation toArray:viewOrder];
[self addDissTapToArray:viewOrder fromData:data inView:view];
}
- (void) cancelIons:(id)sender fromData:(EquationData *)data inView:(UIView *)view withViewList:(NSMutableArray *)viewlist {
if( [sender state] == UIGestureRecognizerStateEnded ) {
FormulaLabel* label = (FormulaLabel*)[sender view];
int index = label.tag;
[data.disEquation removeObjectAtIndex:index];
for (UIView *formulaView in viewlist)
[formulaView removeFromSuperview];
[viewlist removeAllObjects];
[self setUpView:view fromArray:data.disEquation toArray:viewlist];
[self addDissTapToArray:viewlist fromData:data inView:view];
}
}
- (void)addBalanceCell {
[cellOrder addObject:#"balanceCell"];
[table reloadData];
NSIndexPath *myIndexPath = [NSIndexPath indexPathForRow:0 inSection:([cellOrder count]-1)];
[table scrollToRowAtIndexPath:myIndexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
leftBalanceItems = [[NSMutableArray alloc] init];
rightBalanceItems = [[NSMutableArray alloc] init];
}
- (void) addBalanceTapMethodInArray:(NSMutableArray *)balanceItems Data:(EquationData *)data {
FalseTarget *target = [[FalseTarget alloc] initWithVC:self Data:data ViewList:balanceItems view:nil];
for (UIView *view in balanceItems) {
UITapGestureRecognizer* tap = [[UITapGestureRecognizer alloc] initWithTarget:target action:#selector(tap:)];
[view addGestureRecognizer:tap];
}
}
- (void)updateBalanceLabelofSender:(UIGestureRecognizer*)sender fromData:(EquationData *)data inArray:(NSMutableArray *)balanceItems {
FormulaLabel* label = (FormulaLabel*)[sender view];
int oldWidth = label.frame.size.width;
label.text = [data updateBalancedatIndex:label.tag];
[label sizeToFit];
int newWidth = label.frame.size.width;
int difference = newWidth - oldWidth;
int labelIndex = label.tag * 2;
for (int j = 0; j<[balanceItems count]; j++) {
// adjusts coordinate of all views to the right of tapped item
if (j > labelIndex){
UIView *item = [balanceItems objectAtIndex:j];
item.frame = CGRectMake(item.frame.origin.x + difference, item.frame.origin.y, item.frame.size.width, item.frame.size.height);
}
}
}
- (void)setUpView:(UIView *)view fromArray:(NSMutableArray *)equationData toArray:(NSMutableArray *)balanceItems {
int labelCount = 0; //label #
int startingPoint = 5; //x vaiue where first label starts
for (NSString *equationText in equationData) {
//add text
FormulaLabel *tempLabel = [[FormulaLabel alloc] initWithFrame:CGRectMake(startingPoint, 2, 10, 22)];
tempLabel.text = equationText;
[tempLabel sizeToFit];
[view addSubview:tempLabel];
tempLabel.tag = labelCount;
[balanceItems addObject:tempLabel];
//set location of '+'
startingPoint = tempLabel.frame.origin.x + tempLabel.frame.size.width + 3;
if (labelCount != [equationData count]-1) { //not the last label
UILabel *plus = [[[UILabel alloc] initWithFrame:CGRectMake(startingPoint, 5, 10, 10)]autorelease];
plus.text = #"+";
plus.font = [UIFont systemFontOfSize:13];
[plus sizeToFit];
[view addSubview:plus];
startingPoint = plus.frame.origin.x + plus.frame.size.width + 3;
[balanceItems addObject:plus];
}
labelCount ++;
[tempLabel release];
}
}

Answer 1

Why can't you use one view controller class with a question-property where you overload the property's setter method to update the UI to the new data:
in QuestionViewController.h file:
#property (retain, nonatomic) Question* myQuestionData;
in QuestionViewController.m
-(void) setMyQuestionData:(Question*)newData {
[myQuestionData autorelease];
myQuestionData = [newData retain];
[self updateUIElements];
}

Answer 2

I wouldn't do like that, because you are forcing the UIViewController to know about the data model (while making it it's property). What I would do, would be a class and using class methods (and not object methods) would create the data source. You would still have to hold the data in the UIViewController somehow, but I think a NSArray or a NSDictionary would be good enough:
-(void)viewDidLoad{
[superViewDidLoad];
myArray = [MyModel createDataSourceForTag:myTag];
}

Answer 3

I guess here you should go with Model structure.
1. Model: Model represents to entity. Here in your case, there i can create two entities Round, Question
#interface Round: NSObject {
NSUInteger *roundId; // 1, 2 = if it is required to check then this mi
NSArray *questions; // Array that contains objects for Question entity
}
#interface Question:NSObject {
NSString *questionText;
NSString *options1Text;
NSString *options2Text;
NSString *options3Text;
}
#interface DataManager:NSObject {
NSArray *rounds; // Array that contains object for Round entity
}
+(void)sharedInstance;
2. DataManger: DataManager will manage your entity objects. This data manager will be an sharedInstance class. So while initializing manager, entities will be created and data will be inserted.
3. ViewController: Now in view controller you can directly use sharedInstace, like this:
[[DataManager sharedInstance] rounds]
You can easily get code for creating sharedInstance class.
Now you can use this rounds anywhere in the entire application.
So it will be quiet easy to access. For example, if you require 1st round 2nd question 3rd option then, write code for same way
Round 1
Round *r = [[[DataManager sharedInstance] rounds] objectAtIndex:0];
Question 2
Question *q = [[r questions] objectAtIndex:1];
Question Text and Option 3
NSLog(#"questionText : %# 3rd Option: %#", q.questionText, q.option3Text)
Enjoy Coding :)