How to pass an integer to a model class - cocoa

Question

I'm having a bit of trouble with this one! I have definitely looked in to a lot of posts, but can't get it to work. Previously in my app, I have managed to pass data between classes by assigning it to a property. I'm not sure where I'm going wrong here so any help would be appreciated. I know the following code isn't great, and I'm looking in to dictionaries to help, but for now I would like to get this working.
- (IBAction)checkAnswers:(id)sender
{
// The following if statements check user input and checks to see if it is the right answer.
// The .text parts are uitextfield properties and then shows an image of a tick if correct.
// It then assigns one to a variable and sums them up at the end (blag)
if ([eyepiece.text isEqualToString:#"Eyepiece"]) {
UIImage *image = [UIImage imageNamed:#"Tick.png"];
[eyepieceTick setImage:image];
a = 1;
}
if ([focussingKnobs.text isEqualToString:#"Focussing knobs"]) {
UIImage *image = [UIImage imageNamed:#"Tick.png"];
[focussingTick setImage:image];
b = 1;
}
if ([objectiveLens.text isEqualToString:#"Objective lenses"]) {
UIImage *image = [UIImage imageNamed:#"Tick.png"];
[objectiveTick setImage:image];
c = 1;
}
if ([stage.text isEqualToString:#"Stage"]) {
UIImage *image = [UIImage imageNamed:#"Tick.png"];
[stageTick setImage:image];
d = 1;
}
if ([mirror.text isEqualToString:#"Mirror"]) {
UIImage *image = [UIImage imageNamed:#"Tick.png"];
[mirrorTick setImage:image];
e = 1;
}
blag = a + b + c + d + e;
// Here I update a label with the score
finalScore = [[NSString alloc] initWithFormat:#"%D", blag];
[score setText:finalScore];
// This is probably where I'm going wrong. I'm allocating a model class called
// Level_3_Brain and trying to assign a new property in that class (cellsLevelThree)
// with the score.
// Level_3_Brain *level = [[Level_3_Brain alloc] init];
// level.cellsLevelThree = blag;
// Updated to
[Level_3_Brain sharedInstanceOfLevel3].cellsLevelThree = blag;
// I then set them all back to zero so that the score doesn't go above 5
a = 0, b = 0, c = 0, d = 0, e = 0;
blag = 0;
}
My model class .h now has:
#interface Level_3_Brain : NSObject
+ (id)sharedInstanceOfLevel3;
#property (nonatomic) int cellsLevelThree;
#end
My .m now has this code taken from the Singleton article:
#implementation Level_3_Brain
#synthesize cellsLevelThree;
static Level_3_Brain *sharedInstanceOfLevel3 = nil;
// Get the shared instance and create it if necessary.
+ (Level_3_Brain *)sharedInstanceOfLevel3 {
if (sharedInstanceOfLevel3 == nil)
{
sharedInstanceOfLevel3 = [[super allocWithZone:NULL] init];
}
return sharedInstanceOfLevel3;
}
// We can still have a regular init method, that will get called the first time the Singleton is used.
- (id)init
{
self = [super init];
if (self) {
// Work your initialising magic here as you normally would
}
NSLog(#"%#", cellsLevelThree);
return self;
}
// Your dealloc method will never be called, as the singleton survives for the duration of your app.
// However, I like to include it so I know what memory I'm using (and incase, one day, I convert away from Singleton).
-(void)dealloc
{
// I'm never called!
// [super dealloc];
}
/ We don't want to allocate a new instance, so return the current one.
+ (id)allocWithZone:(NSZone*)zone {
return [self sharedInstanceOfLevel3];
}
// Equally, we don't want to generate multiple copies of the singleton.
- (id)copyWithZone:(NSZone *)zone {
return self;
}
#end
Unfortunately, I'm now getting the error "Property 'cellsLevelThree' not found on object of type id. Please help!!

Answer 1

You correctly identified the place where you are "going wrong" in your comment: the problem is not in that you are setting the value incorrectly, but in that you are setting it on a brand-new instance that is local to the method, and is promptly discarded upon the exit from that method.
In general, your model class(es) should be created when your application starts up, and remain available during the entire lifetime of your application. This is often accomplished using singletons.