As with many of my blog posts, it is often a tweet or another blog post that made me want to write my thoughts. In this case it is both:

Just accidentally blew away 16 files' & days' worth of work with hg. Looked up, TIme Machine had just finished. Lost < 1 min. of work.

- @incanus77

That tweet prompted Wolf Rentzsch to write this post about how Time Machine is your version control "safety net". To me both of these are shocking. It seems that the tweeted mishap may have been user error, but it made me look into how the various user interfaces help protect the user.

Your VCS should protect you

For a long while I was opposed to VCSs, mostly due to faffing around with subversion and getting nowhere. With DVCSs I've become an addict. The issue is that DVCSs also try to be clever. Their primary goal is to protect you from yourself, to make sure your code and its history are safe. Essentially your commit history should be like a stack. 99% of the time you push onto the stack, rarely you need to pop off a stack. You can read the contents of the stack as you want. But you shouldn't be able to modify the internals of the stack.

This is why I consider the many rebase plugins/commands in DVCSs to be harmful. I feel that rebase should be viewed as a mixture of goto, premature optimisation and Jeremy Kyle all rolled into one ie don't touch it unless you know what you're doing and are wearing many layers of protection, and even then it probably isn't such a good idea. Some people swear by rebase, but I feel that you shouldn't be messing with what should be treated as sacred.

Your repository is not a toy, so stop playing with it.

Protecting against destructive actions

This is where we get onto UI. I've never really given much thought to command line UIs, but comparing git, Mercurial and Bazaar I've found subtle differences in the UI that make it harder or easier for a user to perform a destructive action. These really fall into 3 categories: confirmations, making it hard to destroy and separating destructive actions.

In the case of the tweet at the start, I looked into the command that was performed: hg update -C . It offers no confirmation dialogue, it just cleans out the items that have changed. It doesn't make it hard to destroy changes and it is a one character option which means it is easy to do. I'm not sure about git but the equivalent in Bazaar would be bzr revert --no-backup. Of course there's no real reason to run --no-backup, it helps save your arse just in case and cleaning it up is just a case of bzr clean-tree --detritus (which lists the files to be deleted and asks for a confirmation).

One of the other examples is from the blog post. git branch -d abranch will delete the branch called abranch. Now to me this seems incredibly dangerous as there isn't any confirmation given. Occasionally I've seen warnings to use the uppercase -D option if changes aren't merged into the parent, but sometimes even those may not appear. If you're doing something like deleting a branch then it should be made harder to do. Really it should be git branch --delete-branch abranch and then ask you to confirm the delete.

Destructive actions should really be moved out into other commands if possible. bzr has 2 such commands: uncommit and clean-tree. Uncommit and clean-tree both list the items that will be removed and ask you to confirm. This makes the user double check what they're doing to confirm what they are doing. Now these commands could be moved into other commands. Uncommit could be made into bzr commit -d, but by separating them out you are making the user think that this is a different thing and making it harder for them.

The hypocrisy of UI design

It does seem very hypocritical, when most of UI design is a push to make life easier for a user, to advocate making it harder. But as odd as it may seem, making something harder may make it more usable. Now by harder I don't mean make a series of convoluted steps that require an animal sacrifice. I mean add an extra step to any potentially dangerous action. Tell the user exactly what the result of the action will be and ask them to confirm it.

Obviously you should provide undo when possible, but sometimes it isn't. Think about where in your UI you place these actions and consider whether you need them there at all. Don't put a 'wipe library' button right next to one of the most commonly used buttons in your UI, and no matter where you put it, if you can't offer an undo then tell the user exactly what you will do and make them confirm. Force them to pay attention to what they are doing. They'll thank you for it, even if it is just by not complaining to you (or worse to the internet) about how your software lost their data without warning.

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At NSConference Dave Dribin made the following statement in a slide:

Delegates are preferable to Notifications which are preferable to KVO

Now this caused a bit of a murmur on Twitter, as it was taken as "KVO is bad". As this is an important topic and not one that can easily fit into 140 characters I thought I would write a post to outline my rules for when to use each technology and why use them where I do.

Rule #1: Always use delegates for 1 to 1 relationships

One of the main reasons delegates were listed as the most preferable is that they provide the least 'magic' way of communicating between objects while keeping them loosely coupled. It sends the message directly to the object and you can see what method is being run. As such it makes your code more self explanatory. So whenever you have a 1 to 1 relationship between two classes, opt for delegation over notification.

Rule #2: Use notifications for communicating events to many objects

Notifications should really be used wherever you would use a delegate, but need to communicate with any number of objects. They should really be thought of as 1 to many delegates. Quite often in Cocoa you will see a case where there is a notification and a delegate method for the same event (eg change of selection in a table view). These are cases where 80% of the time you just need a 1 to 1 relationship, but occasionally do need a 1 to many relationship. You will rarely encounter this in your own code, unless you are building a class for use in multiple apps.

Rule #3: Use KVO for communicating data model changes

This is where I have found KVO to be the most powerful. You need to keep various UI elements in sync with your data model. Changing the value of the model from one view should also update the value in other views. KVO was built for exactly this situation and as such requires much less code than delegation and notifications.

To achieve the same effect with delegation or notifications you would have to add delegate methods or post a notification in each setter method of each model object. This obviously is a lot of code that needs to be written. Code that could have bugs and code that makes your source more cluttered. KVO of a value in an object requires just one line of code and the implementation of one method. And if you use bindings then it is actually no code at all.

Rule #4: Use blocks instead of callback delegates

I'll start with the exception to this: if you have multiple callback options then use delegates (eg NSURLConnection). But the vast majority of asynchronous operations need just a single callback. In these cases, if you are using Mac OS X 10.6, then you should be using blocks instead of delegates. Blocks reduce the layer of indirection in your source by putting the call back information inline with the invocation of the method.

The next two rules aren't quite rules of communication, but are relevant to the discussion at hand.

Rule #5: Comment anything that isn't clear

This should be pretty obvious. If something in your code isn't explicitly clear from the code itself then comment it. If you are sending off a notification say why you are sending it off, so you can get an idea of what it is doing elsewhere in the application.

Rule #6: If something seems like magic, learn how it works

There is no such thing as magic in programming, simply things we don't fully understand. If notifications, delegation, KVO or anything else seems like magic, then read up the documentation on it or ask a developer experienced in that area to explain how it works. When you find out how they work you realise that what seems like magic is fundamentally a very simple process.

Ultimately, what Dave said was right for some scenarios. Each technology has its use case and you should only use it where it is needed. You should always aim for the smallest amount of indirection in your code while still retaining loose coupling of classes. KVO and notifications are necessary in some occasions (unless you want to go crazy with delegation) but they should only be used when they are needed.

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I have seen a lot of questions and comments on the iPad and I feel I need to write my responses to some of them down. So here goes.

Who is the iPad for?

The iPad is for casual computing. It is what many people said the iPhone would be for, before realising that the small screen isn't all that good for casual computing. The iPad really is a remarkable device, showing off the technology combination the iPhone introduced us to in a much better way.

But who is it for? Well it is for everyone. Some people are saying it is for their parents and that it isn't for geeks or professionals. I disagree. Yes it is ideal for those who don't want to learn how to use a computer, but that doesn't mean that it won't also be great for the computer literate. Hell, look at the popularity of the iPhone, that isn't just computer illiterate users. But just because it will work well for everyone, doesn't mean it will work well for every task.

What is its place?

Apple explicitly said that the iPad sits between the iPhone and the Mac. They have specced it out in that range, are marketing it in that range and priced it in that range. It sits in the middle ground, which is exactly the same place that many low end PCs sit. The exact sort of PCs that are bought for workers, schools or just by people who want a computer to get online but don't need anything powerful.

Think of all the people who have to travel around with bulky laptops just to fill out some forms when they see customers. The iPad is a much more portable way of providing that same functionality, for what would be a reasonably similar price.

In education the iPad would be invaluable. With the iBooks system, iTunes U, iWork all on this one lightweight device which costs only a bit more than a low powered laptop, it is the perfect education tool. It becomes the textbook, the educational video and the work machine all in one. With the ability to type but also sketch with your finger it could replace pen and paper for note taking for many people.

And finally think of the casual user. You don't need a bulky computer system any more, you can buy a sleek iPad that you can easily store in a drawer when you don't need it. It is powerful enough for everything a casual user could want, and then some. There is also something else significant I will get to in a bit.

Isn't it just a big iPhone?

From a technical point of view it pretty much is just a big iPhone. Sure it is faster and has different UIs on the apps, but it is running the same fundamental core. But it is very easy to underestimate how important the bigger screen is. There are many applications that work ok on the iPhone but would work so much better on an iPad

In the keynote video the developer of Brushes was brought on stage to show off the app. The extra screen space allows a much bigger canvas with more powerful tools. The iPhone lets you build a toy paint app, the iPad lets you build a real paint app.

The iPhone also doesn't really work for things such as office applications. Pages, Keynote, Numbers. Sure you could do them on the iPhone, but they wouldn't provide a good experience. The iPad offers a screen resolution that allows you to make these sorts of applications possible.

The other key thing is that there are some app concepts that work well on the iPhone but not on the Mac. There are also some that work well on the Mac but not on the iPhone. On the iPad the majority of these concepts from Mac and iPhone work equally well. You can build desktop calibre apps for the iPad, which you couldn't for the small screen of the iPhone.

Surely this means the Mac is dead?

The iPad replacing the Mac is as likely as it replacing the iPhone. The iPad is a 1GHz device with up to 64GB of storage and a 9.5" screen supporting a 1024x768 resolution. For casual computing that is fine. But for high performance tasks? No. For shared media system? No. For doing work that requires very large amounts of screen real estate? No.

For the iPad to replace the iMac for example it would need to have a 27" screen with 2560x1440 resolution, a 2.6GHz quad core processor and 1TB of storage. The fact is that such a machine would be both hugely expensive and incredibly impractical.

In the same way that an average laptop is always less powerful than an average desktop at any period in time, the iPad will always be less powerful than an average laptop. It is basic economics and physics. New high powered processors produce more heat and so need more cooling, over time processors of equivalent power will be made more efficient and smaller. The iPad is 1GHz, Macs reached 1GHz 8 years ago.

The iPad is also a much more personal device. I wouldn't expect to see many groups of people gathering round an iPad to watch a movie. The Mac provides a much better group media system due to the bigger screen size. Throw in the fact that you can add a remote and front row to the Mac and you have a home entertainment system, which the iPad is not.

So why not just chop the keyboard off a MacBook?

Some people wanted a touch screen Mac with no keyboard or mouse. Such a product would fail miserably. This is essentially what a Windows Tablet/Slate/Whatever-they're-calling-them-this-week is. It is a laptop with the keyboard chopped off. And they provide a terrible experience. Not because of the hardware, but because they're running Windows.

Now that isn't to take a jab at Windows. The issue is that Window is a desktop OS. It has been designed for use with keyboard and mouse and doesn't work too well with a touch screen. Like OS X it has some multi touch functionality hacked on, but you are still moving a mouse cursor about and clicking on a 1px point.

A user interface for a touch screen where the primary input method is your finger requires a hugely different user interface. You can't have a 1 pixel line you have to touch and drag as you do with split views. You need to fundamentally change how controls behave as they need larger target areas.

Many parts of a desktop OS are irrelevant as well. Scrollbars aren't needed on a touch screen. They would take up valuable screen space that can otherwise be done by stroking your finger along the screen. Scroll areas are also inverted. Drag a scroll bar down on a desktop and the page moves down, drag your finger down on an iPhone and the page moves up. This is because you no longer have the disconnect between screen and input device.

What about multi tasking?

There have been two large groups of people talking about multi tasking. Those who want it and those who think that casual users won't use it. Both groups are right and wrong. The iPad needs multi tasking, but it doesn't necessarily need to mean multiple apps running at once.

For those who don't think it is needed, I would ask whether you multi task in real life? Yes you do. Off the computer you listen to music while you work. On a computer you flip back and forth between a web page and a word processing document. You do multi task.

What you don't do is use 20+ applications all at once. Sure I have over 20 applications open but I don't use them all. As I'm writing this blog post I'm listening to music while flipping between typing up and researching on the web, with the occasional glance at twitter. Now on the iPad I could just exit to the home screen from Pages and open Safari, find what I want then copy and paste back into Pages. Then if I want to change my music I open up the iPod app and change it there.

The issue is that I am multi tasking whether the iPad allows me or not, but I'm having to go through the awkward process of quitting an app, opening another app, quitting that, opening the previous app. There needs to be a limited ability to switch quickly between a certain set of apps.

One way I have thought of is to use a 4 finger swipe. It would work much like 4 finger swiping on a MacBook Pro trackpad. Swipe horizontally and be presented a list of 'open' apps under your finger which you can choose from. Swipe vertically would bring up the home screen to open a new app. This makes the process much faster.

The best thing about this is that it can still be quitting the applications. I'm just not having to move my finger down to the bottom to press the home button, then back up to where I was on the screen to find the app I want (which may or may not be on a different page of apps). It removes the unnecessary movements of the hand as your switching appears under your finger and also reduces any sort of searching your brain has to do as what you want is in a line of a few choices.

Significance of the 3G networking?

What hasn't been talked about is the significance of the 3G networking deal. This is truly a revolution. No contract, you can sign up and cancel any time you want and it is a low monthly fee. If you only want the one device then this is the easiest way in the world to get on the internet in your own home. No installing filters and routers and modems. No phoning up an ISP to get them to connect you up in the next few weeks.

Sure it isn't the fastest internet, but it is fast enough for most basic uses. This is getting online the Apple way, except unlike the iMac adverts of the late 90s, there really is no step 3.

Final thoughts

The iPad truly is a revolutionary device to those who can see its potential. To those who can't it is just an expensive, large iPhone. At the same time, it won't replace the Mac or the iPhone, it just isn't in the same market as either of them. It does have a few flaws at the moment but these are easily fixed. What is important is that this is a glimpse of one of the future forms of mainstream computing.

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Back in July M Cubed started offering design services. This was meant to be an alternate revenue source to our software that we could rely on. Unfortunately this didn't turn out to be the case. While technically M Cubed is a 2 man operation, it is in reality a 1.5 man operation as Fabio has a separate day job.

Having a day job and then coming home and working nights and weekends leads to a person being worn out very quickly. A lot of our design work was being delayed due to Fabio not having the time or energy to do work and this was also filtering down into design for our products. Minim 2.0 was originally planned for a late november release, but delays in design related stuff meant it kept being pushed back.

The delays meant that the money coming in from design wasn't really worth the effort, and I was unable to help as I'm not exactly icon designer material. This has meant we have had to make the decision to stop offering graphic design services. While we were able to deliver what we hope was high quality products, circumstances meant we weren't able to offer high quality service. It is better to not do a job at all than do a bad job.

While we are stopping our graphic design services, we are introducing two new design services where we can offer a high quality of service as they are areas of design I am able to handle myself: Usability and Accessibility.

There are many services available to Mac and iPhone developers for graphic design. A quick google search will bring up pages of people offering icon or UI design services. But there are very few services that focus purely on usability and none that I have seen that focus on accessibility.

So what will our usability and accessibility design services entail?

Usability

Well in a nutshell, you give us your app and we will pick through the user interface and point out any areas where usability could be improved. We will explain why things are in need of improvement and what items are urgent.

Of course, there are different degrees of usability. You can make any user interface usable, in the sense of doing what the user expects, by following a series of rules. But usability can also be about how a user feels when using your application. Is it just functional or is it enjoyable? Our usability reviews will provide suggestions for areas where your user interface can be re-thought to make it highly enjoyable as well as functional, turning a user who is merely happy with their purchase into one who raves about your app to their friends and co-workers.

Accessibility

Our accessibility reviews will work in much the same way. We will go through your application and highlight areas where accessibility is lacking and give you details on how to fix them. But we are also going to do something a bit crazy. We will also show you how to find and detect the majority of accessibility problems yourself.

"But surely that is what we're paying you for? What is the point of us coming to you if you're just going to tell us how to do this work for free?". Very good questions. The fact is that 90% of all accessibility work is trivial. While I certainly am not opposed to you giving us your money, I believe that it is ultimately a waste of your money and of our time to keep coming to us for help with trivial matters.

What you may need help designing is the non trivial matters. How do you make a custom control accessible and what should the interaction model be for disabled users? What is the flow of my application like for disabled users? In a way, if our usability design is aimed at abled users of your software, our accessibility design is the exact same thing but for disabled users.

Getting an estimate

So how do you procure our services? Send us an email with details of your needs to design@mcubedsw.com and we will get back to you with an estimate of how long we think it will take. We charge an hourly rate so this will give you a good idea of how much you can expect to pay. So get in touch and start getting feedback on the accessibility and usability of your apps today!

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