Trying to understand Objective C warning related to factory method

Question

All,
I'm just beginning learning objective C (I am a C++ programmer by day), and I have a question about a warning I am seeing in my code. I found some really simple example code on the web that used the 'new' factory method to create an instance of an object. Here are the three files:
List.h
#import <objc/Object.h>
@interface List : Object // List is a subclass of the superclass Object
int list[100]; // These are instance variables.
int size;
/* Public methods */
- free;
- (int) addEntry: (int) num;
- print;
/* Private methods */
/* Other programs should not use these methods. */
- resetSize;
@end
List.m
#import "List.h"
@implementation List
+ new // factory method
self = [super new];
printf("inside new\n");
[self resetSize];
return self;
- free
return [super free];
- (int) addEntry: (int) num
list[size++] = num;
return size;
- print
int i;
printf("\n");
for (i = 0; i < size; ++i)
printf ("%i ", list);
return self; // Always return self
// if nothing else makes sense.
- resetSize
printf("Inside resetSize\n");
size = 0;
return self;
@end
main.m
#import <objc/Object.h>
#import "List.h" // Note the new commenting style.
main()
id list; // id is a new data type for objects.
list = [List new]; // create an instance of class List.
[list resetSize];
[list addEntry: 5]; // send a message to the object list
[list print];
[list addEntry: 6];
[list addEntry: 3];
[list print];
printf("\n");
[list free]; // get rid of object
Now, I know that the 'best' way to allocate and initialize an object is through [[List alloc] init], but I'm seeing a strange warning when I compile List.m, and I just want to understand why it's showing up. Here's the warning.
List.m: In function ‘+[List new]’:
List.m:9: warning: ‘List’ may not respond to ‘+resetSize’
List.m:9: warning: (Messages without a matching method signature
List.m:9: warning: will be assumed to return ‘id’ and accept
List.m:9: warning: ‘...’ as arguments.)
It looks like something is assuming that resetSize is a factory method rather than an instance method. The strange thing, though, is that the program works exactly like expected. resetSize is actually called from within the new method correctly.
Any ideas why I'm seeing the error, and how I should get rid of it?
Thanks,
Eric

Answer 1

Thanks for clearing that up for me - it makes sense now. And sorry about the formatting problems - I guess forgetting the {code} tags make a pretty big difference
It's taking a little bit for my mind to switch from C++ syntax to Objective C, but I'm able to visualize the problem and the reason the code I found produced the error.
Thanks again,
Eric