Question

I created a simple UIViewController with a custom init method like this:

-(id)initWithGroupNumber:(NSString *)groupNumber {
if ((self = [super init]) == nil) {
    return nil;
}
self.levelGroup = groupNumber;
return self; }

levelGroup is a property written in the .h file

@property (nonatomic, retain) NSString  *levelGroup;

When I call the method above this way:

    LevelsViewController *lvc = [[LevelsViewController alloc]initWithGroupNumber:@"5"];

the controller is allocated but all the property inside are set to nil. I can’t understand why.

Answer 1

First of all when you deal with classes that have subclass of type mutable (e.g. NSMutableString), use copy.

So, your property should become:

@property (nonatomic, copy) NSString *levelGroup;

Then, inside the UIViewController synthesize the property

@synthesize levelGroup;

and in init do the following:

-(id)initWithGroupNumber:(NSString *)groupNumber {

    if (self = [super init]) {
       levelGroup = [groupNumber copy];
    }
    return self;
}

As written in the memory management guide you should not use self. inside init and in dealloc.

Use your property self.levelGroup to get or set the value.

Remember to release in dealloc:

[levelGroup release];

Hope it helps.