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Re: A question on designated initializers

From Jon Rossen <jonr17@comcast.net>
Newsgroups comp.lang.objective-c
Subject Re: A question on designated initializers
Date 2015-11-22 17:24 -0800
Organization albasani.net
Message-ID <n2tpt4$3pn$1@news.albasani.net> (permalink)
References <n2tcmc$t64$1@news.albasani.net> <n2tgoe$59u$1@news.albasani.net> <louiswu-F7B886.16264522112015@news.giganews.com>

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> You SHOULD use the designated initializer for creating objects of the
> class because it was set up to ensure that the object is initialized in
> a safe and consistent manner.
>
> However, since your new class may be initialized by some other means,
> the basic form of the init should be overridden to make sure that the
> designated initializer is used to create the object.



> Suppose, for instance that you need to create Rectangle instances by
> using only the class name using ...

> NSObject *myRect = [[NSClassFromString(@"Rectangle") alloc] init];
>
> Ensuring that the init method (which you overrode) calls the designated
> initializer will make sure that this behaviour "just works".

Thanks for the response!

I do not understand this example using NSClassFromString that you have 
provided.  In my original post, when I said this was a beginner's 
question, I sort of meant it. :-)  When using your example:
NSObject *myRect = [[NSClassFromString(@"Rectangle") alloc] init]; an 
instance of the Rectangle class is not created.  Was there a typo? Did 
you mean to state: Rectangle *myRect....??

Also, why is the importance of having overridden init specifically 
illustrated by this example using NSClassFromString?  Again, I'm 
assuming that my lack of understanding of the simple example you have 
chosen is the reason why I am not understanding your point.

-jonR

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Thread

A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-22 13:39 -0800
  Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-22 14:48 -0800
    Re: A question on designated initializers Louis Wu <louiswu@ringworld.net> - 2015-11-22 16:26 -0800
      Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-22 17:24 -0800
        Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-23 02:39 +0100
  Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-23 01:18 +0100
    Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-22 16:49 -0800
      Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-23 02:02 +0100
        Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-27 17:19 -0800
          Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-28 13:22 +0100
            Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-28 17:37 -0800
              Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-29 03:45 +0100
  Re: A question on designated initializers Don Bruder <dakidd@sonic.net> - 2015-11-22 19:15 -0800
    Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-23 18:44 -0800
      Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-24 04:58 +0100
        Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-24 16:42 -0800
          Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-25 02:00 +0100
        Re: A question on designated initializers Greg Parker <gparker@apple.com> - 2015-11-25 01:25 -0800
      Re: A question on designated initializers Don Bruder <dakidd@sonic.net> - 2015-11-24 07:38 -0800
        Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-24 15:54 -0800
          Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-25 01:49 +0100
            Re: A question on designated initializers Don Bruder <dakidd@sonic.net> - 2015-11-24 18:51 -0800
              Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-25 04:41 +0100
                Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-25 00:25 -0800
                Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-25 14:16 +0100
                Re: A question on designated initializers Jon Rossen <jonr17@comcast.net> - 2015-11-25 17:30 -0800
                Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-26 03:03 +0100
                Re: A question on designated initializers Don Bruder <dakidd@sonic.net> - 2015-11-25 09:08 -0800
                Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-11-25 18:41 +0100
                Re: A question on designated initializers Don Bruder <dakidd@sonic.net> - 2015-12-02 14:37 -0800
                Re: A question on designated initializers "Pascal J. Bourguignon" <pjb@informatimago.com> - 2015-12-03 00:58 +0100
          Re: A question on designated initializers Don Bruder <dakidd@sonic.net> - 2015-11-24 18:29 -0800

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