Question

I am trying to create an instance of a class, Dog, but the compiler does not recognize the class and won’t instantiate it. I tried copying the initializers from Pet, the superclass, into Dog, but that didn’t make it work. Why can’t I instantiate the Dog object?

Pet.h

#import <Foundation/Foundation.h>

@interface Pet : NSObject
{
    // Some ivars
}

//Randomizer
+(id)randomPet;

//Initializer 
-(id)initName:(NSString *)name
initColor:(NSString *)color
initBreed:(NSString *)breed;

// Getters and setters...

@end

Pet.m

#import "Pet.h"

@implementation Pet

+(id)randomPet
{
   // Empty 
}

-(id)initName:(NSString *)name
    initColor:(NSString *)color
    initBreed:(NSString *)breed;
{
    self = [super init];
    if(self)
    {
        // Initialization...
    }
    return self;

}

@end

Dog.h

#import "Pet.h"

@interface Dog : Pet
-(id)initName:(NSString *)name initColor:(NSString *)color
    initBreed:(NSString *)breed;

// Getters and setters...
@end

Dog.m

#import "Dog.h"

@implementation Dog

+(id)RandomPet
{
    // Snip...
}

- (id)initName:(NSString *)name
        initColor:(NSString *)color
        initBreed:(NSString *)breed;
{
    self = [super init];
    if(self) {
        // Initialization...
    }
    return self;
}

main.m

#import <Foundation/Foundation.h>
#import "Pet.h"
int main(int argc, const char * argv[])
{

    @autoreleasepool
    {
        Dog *d = [[Dog alloc] init]];
    }
    return 0;
}

Answer 1

You have following errors:

1. Instead of #import Pet.h use #import Dog.h

2. Dog *d = [[Dog alloc] init]]; should be Dog *d=[Dog alloc]init];

3. No need to re-define same method in sub class as they are in super class.

Apart from these answer, I would like to add few more things, these are not errors but it will add to your cocoa programming style and habbit :

The method

//Initializer 
-(id)initName:(NSString *)name
initColor:(NSString *)color
initBreed:(NSString *)breed;

does not go with standards, it should have been as :

//Initializer 
-(id)initName:(NSString *)name withColor:(NSString *)color withBreed:(NSString *)breed;

---

In the following lines

int petId;
while(petId != 1 && petId!=2)

What about initializing with petID=0;? If its garbage value become 1 then it will never enter the loop.

---

You can use @property to create property.