Silly programmer.  Word to the wise:  when adding children, think carefully about the attributes being inherited.

I found that that the API has a few gotchas so I thought I’d jot this down to help others if possible.  The first thing you have to do is have an object with a property you want to observe.  Note that this must be a property and not merely an instance variable – and the variable must not be readonly.  Next, you must tell the object that it should report changes to that property.  You do this from where the object can be seen, not from within the object.  If you have an object ‘obj’ with a property ‘event’ you would do this:


[obj addObserver:self forKeyPath:@"event" options:NSKeyValueObservingOptionNew context:nil];


Here’s the gotcha though:  contrary to some of the examples you see in google searches, you cannot set options to 0.  It’s a bit mask without a useful default value, so you need to set it.  You probably want to know the new value of the property in the message, so you should set it to NSKeyValueObservingOptionNew.  If you set it to 0 it will just silently fail to send messages.

Next, in the object doing the observing you need to implement the NSKeyValueObserving Protocol.  Here’s a simple example:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object

   change:(NSDictionary *)change

   context:(void *)context
{
    if ([keyPath isEqualToString:@"event"] )
    {
       // process here

    }

}

Now there’s one more gotcha:  when you change the value of the property in your object, you must use self to force the use of the setter.  For example, you must say:

self.event=NEW_VALUE;

and not just say:

event=NEW_VALUE;

The observer sub-system is tied into the getter and setter methods synthesized as the property.

I hope this helps someone!

[UPDATED]

There’s a great discussion on Hacker News about this – pointing out that I did not use the context pointer when I should have.  I learn yet more about this API.  You can follow the conversation here.

I’m going to do better.  2012 will be a year of more writing.  Watch this space!  And in the meantime, Happy Holidays!

Eddie’s family was from Southern Italy, much to the dismay of his wife’s family from the very far North.  He loved to eat good food and drink scotch.  Cheap scotch, unless someone else was treating.  He was of that generation who remembered the Great Depression and he pinched a penny hard.  But he lived very well after retiring from Bank of America.  After he retired he travelled extensively and spent time in Mazatlan Mexico every spring and fall until he was in his mid-90′s.   An enduring memory I have is Eddie fishing on the beach in Mazatlan as brown as can be.   I swear he could tan under florescent lights, but in the warm Mexican sun he’d turn so brown he was almost black!    And he ate well!  With Italian cooks around him his whole life he got such fantastic meals.  We’d sit after a dinner and talk about all the other meals we’d eaten, the places we’d been, the drinks we’d enjoyed.   And Eddie did like a drink!  I’d often joke that I never saw him drink anything other than coffee in the morning, wine with meals, and scotch anytime he could.  And the occasional beer.    Just a few weeks ago we sat in his living room (his house is next to mine, sharing a backyard) watching the 49ers.  I’d brought him a good beer (Lagunitas IPA).  He’d say “now, that’s a good beer!”

And then he fell.

He probably broke both the collarbone and the shoulder blade, they say.  Nothing they could do about it other than treat the pain.   The walker wasn’t an option anymore – putting any weight on the shoulder was agony.  So we put him in a wheelchair and I helped him into it in the morning, out of it to go to the toilet or to bed.  His appetite dwindled to nothing.   The pain was terrible unless we gave him enough pain pills – and then he’d talk to the paint.   But we adjusted the does as best as we could to make him comfortable. Within a few days he was having a lot of trouble even moving his legs at all to get into or out of bed.  And last Wednesday night we knew after barely getting him into bed that we didn’t have the ability to get him of it again.  We prepared for bed rest and all that would entail.  A nurse came on Thanksgiving day to teach us some turning techniques and to check on him (she was a Saint, by the way).   Turning him on the bed was very painful and the nurse got his pain medicine dose increased, which thankfully put him to sleep.

And that evening he passed away.  Thankfully he did not suffer (beyond the pain of the broken shoulder).  He did not get bed sores, or suffer the indignity of losing control of body functions while in bed.  Eddie would have been mortified by that.  He was a very proud man.   He suffered through none of that.  He passed away in his sleep with his family around him.

We know he’s in a much better place, and he lived a great life full of adventure and travel.  He had family around him constantly.   He had a great life.  But we miss him terribly.

God’s Speed Eddie.  Wherever you are, have a few glasses of their best scotch on me, will you?

I’m not some young kid demanding only the latest with no appreciation for the past.  I learned cobol on punch cards.  I coded my first program on a TRS-80 with 4K of RAM (yes, you young punks, there once was a computer that small).  The first computer I bought with my own money was an Osbourne.  I still remember how excited I was that Linux was ported to the Zaurus.  But I’ve also written Android code and published a game for the iPhone (MultiAlien).  The world has moved on, and fast.  It’s about the web.  It’s about modern operating systems.  My expectations are that modern vendors follow the curve.  I’d still be chasing Android if Google had not risked the livelihood of their whole ecosystem with their ignorance of Intellectual Property rights (which means that Larry will get an even better boat for the next America Cup race).  The only reason RIM has a market at all is that they have tentacles into corporate IT email.  When that is gone…  the company value plummets to NOTHING.  I’m serious.  They have NOTHING that I want.  And when that cliff hits…  you don’t want to have a Blackberry.  And I have carried a Blackberry for 7 years.  Until tomorrow.

Frankly, the game has changed.  I’ll pass on corporate email – or jump through a hoop to read it – to get the rest of the benefits of a real modern mobile device.  A real browser.  Modern enhancements.  A real developer ecosystem.  Hope for tomorrow.  If nothing else, the phone you carry says something about you.  With it?  Or dinosaur?

RIM, you are dead and too stupid to know it yet.  Buying QNX?  What dope did you smoke?  But at least you still have some kind of play.  Microsoft?  Who?  For the first time in my professional career they don’t matter.  Neither does Nokia.  I carried Nokia devices for years and literally prayed for the N800 to change the world.  But the game has changed, and Apple has carried the day.  Microsoft does not matter.  Nokia does not matter.

And as of tomorrow, for me, neither does RIM.  Siri, what time can I pick up my new phone tomorrow?

So I’m guilty of missing a story that ran weeks ago but played out yesterday.  Firefighters were not invited to the 9/11 Memorial in NYC because ‘there wasn’t enough space.’  Really?  I thought this was a joke of some kind when I heard it yesterday.  Seriously?   I get it, there’s not a lot of space at the memorial site.  Yes, the families must be there.  But it could have been possible to have at least some of the first responders present.  One per firehouse perhaps.  I bet if the Mayor’s office had invited the leadership of the fire department to sit down as part of the planning process a plan could have been worked out.   Instead there was an announcement that “we don’t have room for you, sorry.”  Unbelievable.

I’m not seeing any real national coverage, so maybe this blew over and smarter heads prevailed.  But that it never got the reaction it should have really makes me angry.  All of NYC should have been in the streets demanding Bloomberg respect those brave souls.  All the National Press should have run stories.  Obama himself should have demanded them to be present.  The raw stupidity of even pondering for a second that they would not be front and center…  it’s mind boggling.  There’s no excuse for this not being a MUCH bigger story.

Except that we Americans can be such a fickle lot.  What have you done for me lately?  Oh that?  That was a while ago.

It did not used to be that way.  Once upon a time we held memories.  We cherished them.  We remembered those who risked -and gave – it all.

Here’s the rub:  the firefighters didn’t do anything unusual for them that bright Tuesday ten years ago.  They do that stuff every day and every night.  They rush into flames and mayhem and save lives.   They protect property.  They risk death and lung shredding fumes and crippling injury and disfiguring burns – every day.  They never stopped that behavior.

But apparently the Mayor’s office in NYC stopped remembering.  The lack of massive protests by NYC residents means they may have stopped remembering.  The lack of national press means the US might have stopped remembering.

But not me.  I remember.  And I say to those who forgot:  SHAME ON YOU.  The first responders won’t forget when it comes time to race into a burning building to save you or your kids.  They won’t forget.  Because that’s who they are.  May we all be more like them.

So I spent a few minutes early this morning (yes, it is possible to code before 6am)  and fixed all that in the app.  I submitted it again.  And fairly quickly, they approved it for sale.  Lessons learned.

Anyway, MultiAlien is available in the App Store now.  Check it out.  I hope you like it!