Question

-(id)initWithStrAndDate: (NSString *)inString date:(NSDate *)inDate
{
  if (self = [super init])
  {
    [self setStr:inString];
    [self setDate:inDate];
  }
  return self;
}

-(id)initWithStr: (NSString *)inString
{
      return [self initWithStrAndDate:inString date:[NSDate date]];
}

-(id)init
{
  return [self initWithStr:nil];

I am not sure that I know how to use the "designated initializer". First of all isn’t

return [self initWithStrAndDate:inString date:[NSDate date]];

this wrong? Shouldn’t this be:

return [self initWithStrAndDate:inString date:nil];

And also why do we use 3 different initializers? I mean when do we use "-(id)init" or "-(id)initWithStr: (NSString *)inString" or the first one?

Answer 1

There are 3 different initializers so you can use either one of them – neither one of them is wrong, they allow you to init the class with variable data – mostly for convenience as in the end they all do the same thing.

You may init the class with specified string and date (the first and longest initializer),

or you can specify the string only and have the date be set to current time,

or you can have an empty string and current time.

note that calling:

[self init];

is equal to calling

[self initWithStr: nil];

and this in turn is equal to

[self initWithStrAndDate: nil date:[NSDate date]];

So in the end you are calling the same initializer anyway.