Are Objective-C initializers allowed to share the same name?
- by NattKatt
I'm running into an odd issue in Objective-C when I have two classes using initializers of the same name, but differently-typed arguments. For example, let's say I create classes A and B:
A.h:
#import <Cocoa/Cocoa.h>
@interface A : NSObject {
}
- (id)initWithNum:(float)theNum;
@end
A.m:
#import "A.h"
@implementation A
- (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 = [[A alloc] initWithNum:20.0f];
B *b = [[B alloc] initWithNum:10];
[a release];
[b release];
[pool drain];
return 0;
}
When I run this, I get the 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 I reverse the order of the imports so it imports B.h first, I 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 some reason, it seems like it's using the data type defined in whichever @interface gets included first for both classes. I did some stepping through the debugger and found that the isa pointer for both a and b objects ends up the same. I also found out that if I no longer make the alloc and init calls inline, both initializations seem to work properly, e.g.:
A *a = [A alloc];
[a initWithNum:20.0f];
If I use this convention when I create both a and b, I get the right output and the isa pointers seem to be different for each object.
Am I doing something wrong? I would have thought multiple classes could have the same initializer names, but perhaps that is not the case.
