I started learning Objective-C when Apple released the iPhone SDK over a year ago, and started programming in it seriously at the beginning of this year. While there are many things I like about Objective-C as a OO language, there is one thing that continuously bother me.
One of the four main tenant of object-oriented design is Encapsulation. Meaning, the inner working of an object is hidden from public view.
In Objective-C, an instance method can be declared in the implementation file (.m file) in the following ways:
- Implement the method without declaring it in the header file. This is (almost) equivalent to private method in C#/Java.
- Declare the method signature in the header file, and implement the method in the .m file. This is like declaring a method public in C#/Java.
So how does this discourages me from writing good OO code with respect to encapsulation?
If I choose the first option, I have two choices. Either I implement the method before its first usage which does no good with readability re Uncle Bob's Clean Code's newspaper metaphor, OR implement it after and put up with the compiler warning about the method call may not exist.
To get the freedom of placing the method anywhere in the .m file, I have to choose the second option and declare the method signature in the header file. The downside of this is that now the method is exposed as part of the class public interface and break encapsulation. (Yes, I know that the method can still be called without the header file declaration. Again, a compiler warning greets you.)
All three options are undesirable to me. It is really a case of pick my poison! Right now, I choose option one and put the method before first usage. Readability suffers because I like reading methods after the usage but at least the header file is clean and represents the intended public interface.
Update: Martin Pilkington makes a suggestion to me via Twitter. I'll have to try it out and see.
Update #2: Someone else on Twitter also suggests using Extension to solve this issue. The Apple's documentation here (at the end of the page) shows how an extension of a class can be used to define private method, separated from the main class interface definition.
My initial feel? Pretty inelegant workaround to an inherited problem of Objective-C legacy linkage to C. No thanks, I'll stick with declaring private methods before usage.
Leah and I went to Philadelphia on a weekend trip this past weekend. For me, it was two days of experiments. All of which are for our trip to Naples/Pompeii later in July.
Canon 50D
The 50D is a vast improvement over my old 10D, bought way back in 2003. The increase in pixel count is obvious, but it is other much more subtle features that impress me. First, the quick startup time from sleep mode. The 10D takes about 5-10 seconds to wake up, thus sometimes I would miss shots. The 50D wakes up and ready to shoot almost instantaneously. The LCD screen is of course larger but it is the colour rendition that makes me take notice. With 10D, the LCD is always too bright and colour too saturated. The screen is still slightly too bright but the colour is almost spot on so preview is actually accurate. The low(er) noise level on high ISO settings makes it, for the first time for me at least, viable to shoot indoor with ISO1600 without worrying about unusable image. Images are still noisy but at least it is manageable.
Kata DR 467
I've been using a camera hipbag inside my Oakley backpack on trips for a few years now. Mainly so it is not obvious that I'm carrying an expensive digital camera. While that worked fairly well, it was awkward to store and retrieve the camera as I have two bag openings to deal with. Alex Lindsay (from PixelCorp and MacBreak Weekly) on Twitter recommended Kata DR-467 for travelling with DSLR. I looked online as well as touched it for real in B&H before deciding to buy it. After this weekend, I was so glad I bought it! I can't believe I didn't get it earlier. The slide out compartment at the bottom for the camera and lenses are the best feature, making it very easy to store/retrieve camera on the go.
GeoCoder
I've always wanted to geotag my photos so this trip was a perfect opportunity to utilise the built-in GPS in my iPhone to try that. I found on the AppStore this free app, GeoCoder, which claims to make geotagging easy. It was pretty easy to use and I just needed to remember to start a 'recording' in GeoCoder at the beginning of the day and stop it at the end. I was afraid that it would drain my battery quickly but it turned out not to be the case.
I was pretty excited about this whole geotagging thing until I got home and tried to use the GPX files GeoCoder produces in Google Earth. Turns out the iPhone GPS receiver is not sensitive enough to pick up GPS signal when the phone is in my pants pocket! So all I have are a handful of GPS locations whenever I took my phone out for a quick Twitter check or the iPhone happened to have enough signal.
So GeoCoder is out for me for the time being.
For the Naples/Pompeii trip, I have considered using one of my iPhone case and strap it to the Kata's shoulder strap in order to get decent GPS signal for the iPhone. Or I can purchase one of the cheaper GPS recorder and use that instead. I'd probably still need to expose the recorder to the sky somehow though.
A bunch of us from the NY Alt.NET and Stephen Forte have organized a Agile Firestarter event on June 27th. Being the build monkey of the group, I'll be presenting the Continuous Integration session.
Register now on Eventbrite. Ticket is $8 to cover food and drinks.
Let's say you have a nice, big, hi-res photo you want to show to your user on the iPhone. No doubt you want to let your user zoom in to see details of the photo and scroll around, just like the built-in Photos.app.
Most of you would probably come up with something akin to the following structure using Interface Builder:
UIView
|
--UIScrollView
|
--UIImageView
If you are coding the UI by hand, the top level UIView would probably be omitted. This may or may not be relevant to the issue you'll be encountering. See my note at the end.
Now that the view structure is setup, you will probably discover that double tapping to zoom in/out is not implemented out of the box by Apple (surprise!).
"Ok", you thought to yourself, "I just need to implement the touch events in the controller and it will all work."
So you go ahead and added touch event code to the controller class, probably something like this:
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
NSInteger tapCount = [touch tapCount];
if (tapCount == 2) {
[scrollView_ setZoomScale:zoomScale animated:YES];
}
}
When you run the code, you'll find that the touchesEnded method never get called!
Turns out this is actually by design from Apple. touchesEnded and other touch event methods are no-op methods by default. My guess is that this is probably a performance related design decision.
Regardless of why, here is what you need to do to 'fix' this. First, create a new class that inherits from UIScrollView. Then in this new subclass, implements the touch event method that you want to use and passes on the event to the next responder in the list. Like this:
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesEnded:touches withEvent:event];
[self.nextResponder touchesEnded:touches withEvent:event];
}
This will pass on the touch event to the parent UIView in the hierarchy and thus calls the touch method in the controller.
Problem solved!
(One thing I haven't tried is to removed the top level UIView from the hierarchy, and link the UIScrollView to the view outlet in the controller. My hunch is that this may eliminate the need to subclass UIScrollView.)
Let's say you want to use UIActionSheet to show three buttons to the user with a cancel buttons in a UIView, which itself is managed by a UITabBarController:
Your code would probably look like this:
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Action Title" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Option 1", @"Option 2", @"Option 3", nil];
actionSheet.actionSheetStyle = UIActionSheetStyleDefault;
[actionSheet showInView:self.view];
[actionSheet release];
And you'll also probably find that all the 3 option buttons works, but the Cancel one doesn't!
It is because the UIView which the UIAlertSheet belongs to is behind the UITabBarController, and the TabBar's hitTest method gets called before the UIAlertSheet's.
To fix this, it is just a simple matter of using the view from the UITabBarController in the showInView method. Like this:
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Action Title" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Option 1", @"Option 2", @"Option 3", nil];
actionSheet.actionSheetStyle = UIActionSheetStyleDefault;
ApplicationDelegate *appDelegate = (ApplicationDelegate *)[[UIApplication sharedApplication] delegate];
UITabBarController *tabBarController = appDelegate.tabBarController_;
[actionSheet showInView:tabBarController.view];
[actionSheet release];
Last Tuesday I travelled down to Philadelphia to speak at the Philly ALT.NET meeting. Brian Donahue, the group organiser, invited me to talk about my experience of developing iPhone application from a .NET perspective. Over 20 people turned up and I was surprised that most of them already owned an iPhone and a Mac (remember this is a .NET group afterall).
I began with listing out the things require for iPhone development (hardware and software), then moved onto comparing Objective-C/Xcode with C#/Visual Studio. I showed a quick code demo to illustrate my points on language and environment differences. Finally I talked about the good, bad, and ugly things I feel about iPhone development up to this point.
This is the first time I gave this talk and feel the Philly audience got good value from my experience. The event was hosted at Drexel University campus and a few of the iSchool students were in the audience. One of them even came up to me afterward and asked whether I'd be interested in doing more talks on iPhone development for iSchool!
Here are the slides I presented:
One of the attendee also took some videos and I'll post them as soon as I receive the link.
Last Wednesday's NY Alt.NET meeting topic was Continuous Integration. Being a ThoughtWorker and had worked on build and deployment project at an enterprise level, it fells naturally to me to not only prepare the presentation material but also present it.
I was a bit nervous about the presentation, as it has been a while (over a year) since I last stood up in a group setting and presented. But I think it went fine, though of course there are always improvement to be made.
I also have the honour of speaking at Philly Alt.NET meeting on May 5th. The topic is on iPhone development for .NET developer. It is something completely different and still pretty new to me.
Don't know what that stands for*? Watch Alex Blumberg and Adam Davidson from NPR's Planet Money explain our economic crisis on KCRW
*WTFJHOTE = WTF Just Happened To Our Economy?
The elevator company in the ThoughWorks office building (e.g. Viacom building @ 44th St) needs an user experience designer. Who in the right mind would put different door controls on each side of the elevator?
Couple of weekends ago, I was at Redmond for the Alt.NET Seattle conference. As this was my second time there, I was no longer a Open Space/Alt.NET virgin. Just like last year, an amazing amount of discussions were packed into two full days. It was very difficult to pick which sessions to attend, having to decide whether to sit in a technical discussion or a meta-discussion. But with so many people recording videos, it is almost possible to not miss anything. We are not quiet there yet, but I am sure in the future every session would be recorded/streamed in some manner.
Ward Cunningham Keynote
Ward Cunningham showed us the work he did during his time with the Eclipse project on unit testing on a new level of complexity. He calls it SWIM and was implemented in PHP/HTML/CSS/JavaScript. He proposed to start a new open source project to implement the same concept in .NET. This create enough interest to spawn off a separate session later this weekend. (The test case runner was provisionally named Swim Runner. Personally I think it should be named Swimmer!)
Encouraging Open Source in .NET
Last year in Seattle, a similar session was convened to discuss how to create more buzz and interest in open source projects in .Net space. This year's session centered around how we can get more open source projects to start, worked on, and succeed. Scott Hanselman hosted this session and asked what the community can do. Should Microsoft give Oren Eini a mail-order bride so he can finish LINQ-to-NHibernate? (Joke) What about OSS projects adaption by VB.NET developers?
.NET/Mono on Mac, Linux, and iPhone
Miguel de Icaza of the Mono Project hosted the session. He showed us the tooling and technique to develop iPhone app/game using the Mono stack on the Mac. He also demonstrated autogeneration of linux bootable image with pre-configured apps. (Side observation #1: only a few people at last year Alt.NET Seattle had iPhones, this year very few people has phones that *isn't* an iPhone. Since this year's event was just before MVP Summit, there are lots of MVPs there with iPhones! Just to show loyalty does not lie with brand but usability! #2: Less than 1/3 of attendees aware of Twitter last year, this year, very few are *not* on Twitter.)
Why so mean?
Hosted by Scott Hanselman. We explored why there is an perception of elitism in the software developer community. Why C# developers talk down to VB.NET developers, why average Microsoft developers are dimmed un-savable. This discussion led to a new session on Sunday about teaching, ALT.NET Pedagogy.
Oxite Retrospective #2
When the Oxite project (a sample blogging engine created using ASP.NET MVC framework) was put up on CodePlex, it created a huge controversy in the Alt.NET community. This is the second part of the retrospective on the project and the aftermath. One of the Oxite team member from Microsoft joined us on Sunday and gave his point of view from the inside.
When to use F#?
With F# being the first class language within the Visual Studio ecosystem, functional programming is gathering more interest. When is functional programming be appropriate for a .NET project? What type of problem would it solve better than plain old C#/VB.NET? Why not just use F# for everything?
Abstract Test Assertions
The ASP.NET MVC Contrib project relies heavily, of course, on TDD. An interesting problem arise when contributors want to develop using different unit testing framework. This session explored the idea of abstracting test assertions so that any frameworks can be used for the project, and what technique should be employed to achieve that.
I've recorded all these sessions on video for those who couldn't attend. Scott Hanselman also streamed live via Kyte.tv for a number of sessions. My videos can be viewed on Vimeo, with the rest of video links on the Alt.NET wiki.
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Recent Comments
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Alex said:
Interesting. I haven't been targetting 2.2.x so I didn't notice the difference in behavior. I don't have any issue with... read more
on UIScrollView and Multi-Touch zooming -
hatfinch said:
Oops, not sure where the second half of my post above got to. I was going to say, 3.0 has... read more
on UIScrollView and Multi-Touch zooming -
hatfinch said:
[this is good]Hi Alex,Thanks for your post. I'm trying to create a UIScrollView subclass that handles zooming properly (i.e. doesn't alter the... read more
on UIScrollView and Multi-Touch zooming -
Mattijas said:
Aha, I understand. you have to keep summarizing the possible numbers of pairs, trios, quartets, etc as the team is... read more
on The Parkinson's Limit and agile team size
The problem with UIScrollView is that it seems to have been designed in two separate halves: the scrolling mechanism being... read more
on UIScrollView and Multi-Touch zooming