Dedicated Initializer in Objective-C - objective-c

Question

I am newbie to Objective-C. I have a 'XYZPerson' Class with attributes {firstName, lastName, dateOfBirth} and I want when I write "XYZPerson *person=[[XYZPerson alloc] init]" in main, it should call my overridden 'init' method which should in-turn call my designated initializer and initializes my object with the defined values.
My Code snippets. http://pastebin.com/FfxNDDhf
#import <Foundation/Foundation.h>
#import "XYZShoutingPerson.h"
int main(int argc, const char * argv[])
{
#autoreleasepool {
XYZPerson *person=[[XYZPerson alloc] init];
if(person) {
[person sayHello];
}
else {
NSLog(#"Person Object is NULL");
}
}
return 0;
}
-(id)init
{
self=[super init];
return [self initWithFirstName:#"Ankit" LastName:#"Sehra" DOB:01/01/2000];
}
-(id)initWithFirstName:(NSString *)aFirstName LastName:(NSString *)aLastName DOB:(NSDate *)aDateOfBirth
{
_firstName=aFirstName;
_lastName=aLastName;
_dateOfBirth=aDateOfBirth;
}
-(void)sayHello;
{
NSLog(#"%# %# %#",self.firstName,self.lastName,self.dateOfBirth);
}
Write now the output of the program is "Person Object is NULL", I want it to print the firstName, lastName and DOB.

Answer 1

If a class has several init methods, one of them is the "designated initializer".
This is the one that calls [super initXXX]. In your example, initWithFirstName:LastName:DOB: would be the designated initializer and should look like
this:
-(id)initWithFirstName:(NSString *)aFirstName LastName:(NSString *)aLastName DOB:(NSString *)aDateOfBirth
{
self = [super init];
if (self) {
_firstName=aFirstName;
_lastName=aLastName;
_dateOfBirth=aDateOfBirth;
}
return self;
}
(I have changed the type of the dateOfBirth property and the DOB argument to NSString and will explain that later.)
All other init methods just call the designated initializer (and not [super initXXX]), in your example init:
-(id)init
{
return [self initWithFirstName:#"Ankit" LastName:#"Sehra" DOB:#"01/01/2000"];
}
Note that (among several other errors), "01/01/2000" is not a NSDate, so
return [self initWithFirstName:#"Ankit" LastName:#"Sehra" DOB:01/01/2000];
does not make any sense. Therefore, to get a first working example for you, I have
changed the argument type to NSString.

Answer 2

I'd bet the compiler is giving you plenty of warnings on that code. You should fix them. If it isn't, your compiler isn't tuned correctly.
First, your designated initializer doesn't return anything.
Secondly, there is no reason to override init and call your designated initializer. Simply do:
foo = [[Person alloc] initWithFirstName:#"bob" lastName:#"dobbs"];