selector - Are Objective-C initializers allowed to share the same name? -

i'm running odd issue in objective-c when have 2 classes using initializers of same name, differently-typed arguments. example, let's create classes , b:

a.h:

#import <cocoa/cocoa.h>  @interface : nsobject { }  - (id)initwithnum:(float)thenum;  @end 

a.m:

#import "a.h"  @implementation  - (id)initwithnum:(float)thenum {     self = [super init];     if (self != nil) {         nslog(@"a: %f", thenum);     }     return self; }  @end 

b.h:

#import <cocoa/cocoa.h>  @interface b : nsobject {  }  - (id)initwithnum:(int)thenum;  @end 

b.m:

#import "b.h"  @implementation b  - (id)initwithnum:(int)thenum {     self = [super init];     if (self != nil) {         nslog(@"b: %d", thenum);     }     return self; }  @end 

main.m:

#import <foundation/foundation.h>  #import "a.h" #import "b.h"  int main (int argc, const char * argv[]) {     nsautoreleasepool * pool = [[nsautoreleasepool alloc] init];      *a = [[a alloc] initwithnum:20.0f];        b *b = [[b alloc] initwithnum:10];      [a release];     [b release];      [pool drain];     return 0; } 

when run this, following output:

2010-04-26 20:44:06.820 fntest[14617:a0f] a: 20.000000 2010-04-26 20:44:06.823 fntest[14617:a0f] b: 1 

if reverse order of imports imports b.h first, get:

2010-04-26 20:45:03.034 fntest[14635:a0f] a: 0.000000 2010-04-26 20:45:03.038 fntest[14635:a0f] b: 10 

for reason, seems it's using data type defined in whichever @interface gets included first both classes. did stepping through debugger , found isa pointer both , b objects ends same. found out if no longer make alloc , init calls inline, both initializations seem work properly, e.g.:

a *a = [a alloc]; [a initwithnum:20.0f]; 

if use convention when create both , b, right output , isa pointers seem different each object.

am doing wrong? have thought multiple classes have same initializer names, perhaps not case.

the problem +alloc method returns object of type id compiler can't decide method signature use. can force application choose correct selector in number of ways. 1 cast return alloc, so:

a* = [(a*)[a alloc] initwithnum:20.f]; b* b = [(b*)[b alloc] initwithnum:10]; 

or override alloc on class , return more specific, although wouldn't myself. so:

+ (a*)alloc { return [super alloc]; } 

finally, , chose, make selectors more descriptive:

// a.h - (id)initwithfloat:(float)thenum;  // b.h - (id)initwithinteger:(int)thenum;