Making pointer from integer in Objective C

Question

After programming with C# and Java for many years I finally decided to learn Objective-C in order to start programming iOS Devices as well as Mac OS X, and I have to admit it is very different then most modern c-based programming languages. I am getting the following warning in my code:

warning: passing argument 1 of 'SetAge' makes pointer from integer without a cast

Here is my code:

Dog.h

#import <Cocoa/Cocoa.h>


@interface Dog : NSObject {
    int ciAge;
    NSString * csName;
}

- (void) Bark;
- (void) SetAge: (int *) liAge;
- (void) SetName: (NSString *) lsName;

@end

Dog.m

#import "Dog.h"

@implementation Dog

- (void) Bark
{
    NSLog(@"The dog %@ barks with age %d", csName, ciAge);  
}

- (void) SetAge: (int *) liAge {
    ciAge = (int)liAge;
}

- (void) SetName: (NSString *) lsName {
    csName = lsName;
}
@end

HelloWorld.m

#import <Foundation/Foundation.h>
#import "Dog.h"


int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    int liTemp = 75;
    NSString * lsCity = @"Chicago";
    NSDate * loDate = [NSDate date];

    // insert code here...
    NSLog(@"The temperature is %d currently in %@, on %@", liTemp, lsCity, loDate);

    int liAge = 10;

    // Call Dog class
    Dog * Dog1 = [Dog new];
    [Dog1 SetAge:(int)liAge]; // The Warning happens here
    [Dog1 SetName:@"Fido"];

    [Dog1 Bark];


    [pool drain];
    return 0;
}

My Questions Are:

1. How do I get rid of the warning above?
2. Instead of creating methods in the Dog Class for setting Age and Name, how could I have make Age and Name public class level variables that I could directly assign to?

Any help would be much appreciated!

Thanks, Pete

Answer 1

Don't declare an int as a pointer. Change your code from:

- (void) SetAge: (int *) liAge

to

- (void) SetAge: (int) liAge

and

- (void) SetAge: (int *) liAge {
    ciAge = (int)liAge;
}

to

- (void) SetAge: (int) liAge {
    ciAge = liAge;
}

Consider making age and name a property. Change:

- (void) SetAge: (int *) liAge;
- (void) SetName: (NSString *) lsName;

to

@property (nonatomic, readwrite) NSInteger age; //Don't declare as pointer
@property (nonatomic, retain) NSString *name; //DO declare as pointer

Also, don't forget to synthesize them in your implementation file:

@synthesize age, name;

Answer 2

int is a C primitive scalar type so you don't need pointers. Don't use *.

Warning here

int * represents a pointer variable, a thing you're not used to see in C# or in Java.

int *p is a variable that will point to a memory address. To put data at this address you have to dereference the variable p before using it ex:*p = 3.

Objective-C is based on the C language and this is a C language problem. You should (must ?) read about C and pointers if you want to code in Objective-C.

And read also how Objective-C simplifies your life with pointers to objects particularly the fact that you don't have do explicitly dereference them to use them.