iPhone Application Error Problem - iphone

Question

Bear with me on this one.
I have an iphone application. It is a questionnaire application. There are several types of question, some have a slider, some have text input etc. I have developed a view controller for each type of question.
Two example types of question controllers are: TextInputQuestionViewController and SliderQuestionViewController.
I have a rootViewcontroller named QuestionnaireViewController. This is defined as follows:
#import <UIKit/UIKit.h>
#import "JSONKit.h";
#import "dbConnector.h"
#import "SliderQuestionViewController.h";
#import "TextInputQuestionViewController.h";
#import "MainMenuProtocol.h";
#interface QuestionnaireViewController : UIViewController {
NSDictionary* questions;
NSMutableArray* questionArray;
NSMutableArray* answerArray;
dbConnector* db;
SliderQuestionViewController* currQ; //need to create a generic var
TextInputQuestionViewController* currQ;
NSInteger currQNum;
NSString* qaTitle;
NSString* secId;
id<MainMenuProtocol>delegate;
}
#property(nonatomic, retain) NSDictionary* questions;
#property(nonatomic, retain) NSMutableArray* questionArray;
#property(nonatomic, retain) NSMutableArray* answerArray;
#property(nonatomic, retain) dbConnector* db;
#property(nonatomic, retain) SliderQuestionViewController* currQ;
#property(nonatomic, retain) TextInputQuestionViewController* currTI;
#property(nonatomic) NSInteger currQNum;
#property(nonatomic, retain) NSString* qaTitle;
#property(nonatomic, retain) NSString* secId;
#property(nonatomic, retain) id <MainMenuProtocol> delegate;
-(void) setQuestions;
-(void) startQuestion:(NSInteger)index isLast:(BOOL)last;
-(void) loadQuestions;
-(void) initialise;
-(void) finishQuestionnaire:(id)sender;
-(void) switchViews:(id)sender;
#end
#import "QuestionnaireViewController.h"
#import "dbConnector.h"
#import "ASIHTTPRequest.h"
#import "JSONKit.h";
#import "Answer.h";
#implementation QuestionnaireViewController
#synthesize questions, questionArray, db, currQ, currQNum, answerArray, qaTitle, secId, delegate;
-(void)viewDidLoad{
[self initialise];
answerArray = [[NSMutableArray alloc]init];
[super viewDidLoad];
self.title = qaTitle; //set to whatever section is
}
-(void) initialise {
currQNum = 0;
[self loadQuestions];
UIBarButtonItem *anotherButton = [[UIBarButtonItem alloc] initWithTitle:#"Start" style:UIBarButtonItemStylePlain target:self action:#selector(switchViews:)];
self.navigationItem.rightBarButtonItem = anotherButton;
}
-(void) loadQuestions {
db = [[dbConnector alloc]init];
//code to initialise view
[db getQuestions:secId from:#"http://dev.speechlink.co.uk/David/get_questions.php" respondToDelegate:self];
}
//called when questions finished loading
//stores dictionary of questions
- (void)requestFinished:(ASIHTTPRequest *)request
{
NSData *responseData = [request responseData];
NSString *json = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
NSDictionary *qs = [json objectFromJSONString];
self.questions = qs;
[json release];
[qs release];
[self setQuestions];
}
//assigns JSON to question objects
-(void) setQuestions {
questionArray = [[NSMutableArray alloc] init];
for (NSDictionary *q in self.questions) {
/* Create Question object and populate it */
id question;
if([[q objectForKey:#"type"] isEqualToString:#"Slider"]){
question = [[SliderQuestionViewController alloc]init];
//set min max values
}else if([[q objectForKey:#"type"] isEqualToString:#"Option"]){
}else if([[q objectForKey:#"type"] isEqualToString:#"TextInput"]){
question = [[TextInputQuestionViewController alloc]init];
}else if([[q objectForKey:#"type"] isEqualToString:#"ImagePicker"]){
}else{
//comments
}
//if else to create appropriate view controller - NEED to identify question type
[question setQuestionId:[q objectForKey:#"questionId"] withTitle:[q objectForKey:#"question"] number:[q objectForKey:#"questionNumber"] section:[q objectForKey:#"sectionId"] questionType: [q objectForKey:#"type"]];
/* Add it to question (mutable) array */
[questionArray addObject:question];
[question release];
}
}
-(void) startQuestion:(NSInteger)index isLast:(BOOL)last{
//currQ = [[QuestionViewController alloc]init];
currQ = [questionArray objectAtIndex:index];
//push currQ onto navigationcontroller stack
[self.navigationController pushViewController:currQ animated:YES];
[currQ addButton:self isLast: last];
}
//pushes new view onto navigation controller stack
-(void) switchViews:(id)sender{
Answer* ans = currQ.question.answer;
ans.questionId = currQ.question.qId;
ans.entryId = #"1";//temporary;
if(currQNum < [questionArray count] - 1){
if(currQNum > 0){
//if else for different input types
NSString* qt = currQ.question.qType;
if([qt isEqualToString:#"Slider"]){
ans.answer = currQ.sliderLabel.text;
}else if([qt isEqualToString:#"Option"]){
}else if([qt isEqualToString:#"TextInput"]){
//NSLog(#"%#", currQ.inputAnswer);
ans.answer = currQ.inputAnswer.text;
}else if([qt isEqualToString:#"ImagePicker"]){
}else{
}
[answerArray addObject: ans];
[ans release];
}
[self startQuestion:currQNum isLast:FALSE];
currQNum++;
}else{
ans.answer = currQ.sliderLabel.text;
[answerArray addObject: ans];
//store data temporarily - section finished
[self startQuestion:currQNum isLast:TRUE];
currQNum++;
}
[ans release];
}
-(void) finishQuestionnaire:(id)sender{
//go back to main manual
//if else statement for answers
NSString* answ = currQ.sliderLabel.text;
[answerArray addObject: answ];
[delegate finishedSection:answerArray section:secId];
[answ release];
[self.navigationController popToRootViewControllerAnimated:YES];
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
self.questions = nil;
self.currQ = nil;
[super viewDidUnload];
}
//hide back button in navigation bar
- (void) viewWillAppear:(BOOL)animated{
self.navigationItem.hidesBackButton = YES;
}
- (void)dealloc {
[currQ release];
[db release];
[questionArray release];
[questions release];
[super dealloc];
}
#end
the problematic lines with the above are in the switchViews function. I need to make the answer equal to the specific input component in that question view (slider value, text input value). So I need to make currQ a type that can be instantiated using any view controller.
I therefore need a generic variable to hold the current question. currQ holds the current question, but at the moment is of type SliderQuestionViewController. I tried to change this to id, but it throws a load of "Request For member...not a structure of union" and also a load of misassigned pointer issues.
Let me know if you need more code.

Answer 1

This reads like you want a pointer for a UIViewController, so just use that as the type. Then you can cast it down to whatever subclass you like later. For example:
-(void)myAction:(UIViewController *)vc {
SpecialViewController *svc = (SpecialViewController *)vc;
...
}
In your case, declare
UIViewController* currQ;
and then cast it as needed in the implementation to access the different properties and methods of your two subclasses.

Answer 2

If you're looking for a 'generic' variable, you should be able to use id. Make sure you don't define the type as id*, the asterisk should not be present.
A better idea, though, is to create a superclass for your question viewcontrollers. Create a superclass called QuestionViewController that inherits from UIViewController and have the Slider and TextInput (and any others) inherit from QuestionViewController. Then you can define your variable as: QuestionViewController* currQ; You can put any common functionality in that superclass as well and eliminate duplication.