A documentary

For the past few months, I’ve been helping a couple of talented filmmakers with a new project. I’ve been making introductions, reminding busy people to find some time for an interview, and that kind of thing. Today, the result was made public and it’s better than I ever imagined.

I think this project that looks at our past is important for two reasons: our present and future.

It’s no secret that the art and business of software development has changed radically since that day in January 2007. Listening to my colleagues talk about what that moment meant to them is incredibly helpful for putting today’s situation in perspective. You don’t give a shit how big the next iPhone’s screen is going to be when your peers are talking about how these devices have changed their lives.

By funding this project, you’re also giving your future self a rare gift. I was a young developer when the Mac was announced in 1984, and let me assure you that many of the details of that time have been lost over the course of thirty years. You’re going to look back at this time in your career fondly and wish you remembered more about it.

Something like what Andy Hertzfeld has done at Folklore.org has been a godsend to those of us who were around in the early days of the Mac. But I don’t think that approach would work now: the Internet made the iPhone a world-wide phenomenon, not a project limited to the Texaco Towers. (Did you know that the first person to make money from selling apps was a developer in New Zealand?)

This is your chance to create a record of something that has changed so many lives. Please take a moment to look at what Jake and Jed have done and join me in contributing to this Kickstarter.


An anonymous individual is spreading accusations that I’m a patent troll. Hard to believe, huh?

It makes me furious that I have to respond to these claims without knowing my accuser, but here goes:

Yes, we have a patent. Yes, we got a license fee for it. No, it wasn’t unreasonable.

We originally got the patent as protection against a large company, like Adobe, using our innovation. Patents are like trademarks, you have to protect them after you get them (by collecting licensing fees, even if it’s a small one.) The arrangement with Ricci Adams was amicable from the first email to the last.

From a monetary point-of-view, all I’m going to tell you is that the fee we collected from Ricci Adams was less than the amount of time and money spent getting the legal documents in place. We didn’t profit from it, nor did it “stifle competition.” (Pixel Winch is a great product, you should check out the beta. And no, I’m not making any money by saying that.)

We also acquired this patent before our encounter with Lodsys. Our view of patents has obviously changed since then. I can’t go into any specific details there, thanks to the lawyers.

And you want to know the real kicker? After talking about this stuff with my friend Marco Arment, we’re no longer sure that software patents have the same “use it or lose it” conditions as with a trademark. Of course, for a lawyer who’s collecting fees, mentioning this is not in their best interest.

Any further comment on this situation will have to wait until the coward who’s making these claims comes forward.

P.S. Marco, I could use that beer now.


We witnessed something amazing yesterday: a WWDC keynote that will be remembered for a long time. And not for the reason you might expect.

As developers, it’s easy to focus on the fantastic software that was announced: a UI refresh that’s getting a thumbs up from designers and developers alike, great new user-facing features in iOS and OS X, and literally thousands of new APIs that let developers do new and amazing things with their apps. We even got a new programming language!


But that all pales in comparison to the undercurrent for all these changes: Apple has a newfound confidence in itself. It’s at the top of its game, and it knows it.

This is personified by the man who ran the show: Craig Federighi. It was only four years ago that we first saw him on stage at an Apple event. His shaking hand is still painful to watch, especially if you’ve felt that same fear while giving a presentation on stage. Yesterday, we saw a different man, one that owned the stage and the products being presented.

With this confidence, we’re starting to see some important cultural change in the company.

  • Legal agreements that lets developers talk about technologies without breaking confidentiality.
  • Opening up proprietary technologies like iCloud: providing more transparent access, without hiding things through opaque APIs.
  • Improvements to the App Store that give developers better ways to manage and sell their products.

This confidence manifests itself in many ways. When was the last time you heard an Apple executive tout the best product line he’s seen in 25 years?

In short, with confidence comes a new kind of openness. As developers, we’ve always struggled with a company that doesn’t want to give anything away. Yesterday, that started to change.


In just under 12 days, Apple is going to introduce a new look and feel for Mac OS X. This is going to be much more disruptive than it was for iOS 7.

On iOS, an app takes up the entire screen and becomes an extension of the device. It’s also something you’re “in and out” of on a regular basis. It’s not the end of the world if one or more of your apps still looks like iOS 6 because it’s not competing with anything else and the pain is short-lived. Bank of America’s app is still on iOS 6, but I use it infrequently and usually just to deposit checks.

But on the Mac, an app usually shares the display with other apps. And they’re something that you use continuously. If a customer’s Email, Web, Calendar, Contacts and other built-in apps are using a fresh, new look, they’re going to feel put out when they switch to your app and get a legacy appearance.

You will stick out like a sore thumb.

We’ve already started the process on our own apps and are gearing up to help our clients adapt. If you haven’t carved out a large chunk of time this summer to do the same for your own app, do it now.

Get Ready for June 2nd

There’s no doubt in my mind that Apple is going to overhaul the look of Mac OS X in the next version. As more and more apps bridge the gap between the desktop and mobile, the lack of consistent branding and design across platforms is becoming a problem.

I fully expect to see flatter user interfaces, squircle icons, a new Dock, and Helvetica Neue as the system font. We’ve already explored a flattened UI and new icons in xScope, but I was still left wondering what the app would look like with Helvetica Neue as the system font. There’s a lot of custom drawing in xScope and I was pretty sure there would be some areas where sizing and placement would be wrong because the metrics for Lucida Grande were assumed.

So I wrote this.

This category swizzles the NSFont class methods to return a different system font. The instance method to initialize a font from an archive (like a XIB) is also swizzled and the font is replaced if it’s Lucida Grande. The MAC_OS_X_VERSION_NT definition is both an inside joke and a way to make sure your code can adapt to any font.

Here’s what one of the new tools in xScope 4 looked like before using the category:


And here it is with Helvetica Neue as the new system font:


As you can see, there are lots of small misalignments, both in my custom controls and the ones provided by Apple.

Changing the system font will be a bit like the transition to the Retina Display: lots of small tweaks to keep our apps looking perfect. Now would be a good time to start looking for areas where your app is going to need work.


I recently appeared with John Gruber on The Talk Show. During the episode, the following exchange took place:

When it comes to naming characters, the Unicode standard is the bible. And code point U+0040 is named as “COMMERCIAL AT”.

So yeah, we’re “right.”

But then Twitter got ahold of this exchange and I quickly realized something important: we don’t all speak English:

It turns out “arroba” has a very interesting history that originated in Spanish commerce:

“Whatever the origin of the @ symbol, the history of its usage is more well-known: it has long been used in Spanish and Portuguese as an abbreviation of arroba, a unit of weight equivalent to 25 pounds, and derived from the Arabic expression of “a quarter” (الربع pronounced ar-rubʿ)”

As someone who loves iconography, it’s pretty amazing to see @ as a handwritten symbol in 1148:

I also realized that I knew the Italian word for the @ symbol: “chiocciola”. It’s one of the names for a snail (the other being “lumaca” which is commonly used when ordering them in a restaurant.)

And why is this name used?

(It’s fun to say, too. Something like “key-o-cho-la” but with more exotic hand gestures.)

This tweet led to many responses that show how varied the pronunciations are in different languages.

  • Dutch: “apenstaartje” = “monkey tail”
  • Hebrew: “strudel” = shape of the cake
  • Danish/Swedish: “snabel-a” = “with an (elephant) trunk”
  • German: “Klammeraffe” = “spider monkey”
  • Poland: “małpa” = “monkey”
  • Korean: “골뱅이” (gol-baeng-ee) = “a type of sea snail”

Wikipedia has a full list of how @ is used in other languages.

But do you notice the pattern with these pronunciations?

They’re being used as pictograms:

“A pictogram…, is an ideogram that conveys its meaning through its pictorial resemblance to a physical object. Pictographs are often used in writing and graphic systems in which the characters are to a considerable extent pictorial in appearance.”

While pictograms are fairly common in Asian languages, it’s rare to see this kind of usage in the West. Written Kanji characters, such as 木 for “tree”, have been in use since the first century AD. Indeed, these kinds pictures were man’s first form of expression and communication.

But in these writing systems, someone saw a thing with a trunk and leaves growing from the ground and put it on a piece of paper as an 木 symbol. What we’ve seen happen with the @ symbol is the opposite. Many different cultures have seen our “COMMERCIAL AT” symbol and given it a name based on its appearance.

So even though John and I are right about the pronunciation, this is certainly a case where English pales when compared with other languages. I envy my colleagues that get to play with snails and monkeys while coding in Objective-C!

Wearing Apple

Tim Cook has openly stated that Apple is working on “new product” categories. Many people, customers and competitors alike, assume that means some kind of wearable computing device. And of course that means it has to be some kind of “smartwatch”, right?

I don’t think so.

The Market

First, let’s look at the market for quality timepieces; ones that you’d be proud to wear on your wrist. It’s dominated by companies with centuries of experience. It’s also a high-end market: spending a few thousand dollars on a nice watch is chump change. You’re buying a work of art.

Apple certainly has great designers, but they’re going to be competing against craftsmen who’ve been refining their craft since the 15th century.

I realize that this sounds a lot like Ed Colligan talking about mobile phones:

“PC guys are not going to just figure this out. They’re not going to just walk in.”

There’s a big difference here: the companies that dominated the music player and mobile phone markets were making complete crap prior to Apple’s arrival. Granted, there are a lot of cheap and crappy watches on the market, but they’re not remotely interesting to the demographic that buys Apple products. And to many people, a fine timepiece is more about status than technology.

Taking all of this into consideration, watches don’t sound like product category that fits Apple well. One of the many reasons we love their products is because they are best of breed.

The Watch

Now, let’s look at the state of the “smartwatch” market. Smart companies, like Nike and FitBit, are creating products that aren’t really a “watch”. It’s like the “phone” being the least interesting thing on our “smartphone”.

In fact, Tim Cook is already wearing one of these devices:

Walt: Is wearables a thing — is it part of the post-PC era wearables that go beyond fitness devices?

Tim: Yes, I think so. I wear a Fuelband, I think Nike did a great job.

Note: This quote, and others in this piece, were made during Tim Cook’s interview at D11.

However, once manufacturers try to put a lot of smarts in a watch, they end up with a product that’s a bulky mess or ugly as sin. Probably both.

Again, Tim Cook has noticed this same thing:

“There are lots of gadgets in the space. I would say that the ones that are doing more than one thing, there’s nothing great out there that I’ve seen. Nothing that’s going to convince a kid that’s never worn glasses or a band or a watch or whatever to wear one. At least I haven’t seen it. So there’s lots of things to solve in this space.”

We all know that Apple’s designers and developers can solve these problems. But can they do it without making compromises?

“It’s an area that’s ripe for exploration, it’s ripe for us to get excited about. Lots of companies will play in this space.”

That exploration is all about saying no a thousand times. It’s easy to create a great looking concept, but turning that fantasy into a product is where it gets hard and compromises are often made.

It’s my view that the technology needed to make that great product that does everything just isn’t there yet. There are too many compromises.

The New Hub

Let’s assume for a second that you can make a compelling device for a wrist. I’d still be asking myself this question: “Why do I need a computer on my wrist?” I already have one in my pocket.

With the introduction of CarPlay, Apple’s answer to this question is becoming clearer. That device in your pocket is the new hub for your digital data. Ben Thompson calls it Digital Hub 2.0.

You don’t need a computer on your wrist. Apple’s wearable devices will become a part of this circle that surrounds your main device. And as with CarPlay, it’s going to be a two-way street where interactions and information in the player make their way back to the main device.

The Fashion

The development of wearable technology is going to enter a space where most companies in the Silicon Valley have no experience. As a geek, do you know who Anna Wintour is and why she would be important to the success of a wearable device?

Angela Arhendts certainly does…

Put aside your geek sensibilities for a second and think about this device as a piece of fashion instead of a cool gadget. What’s the primary function of fashion?

It’s about expressing a personal style. It’s an extension of your personality and way to show it in a public way.

Look at the huge variety of iPhone cases that are on the market. That’s only 16 examples of 4.7 million search results. Fashion is as diverse as the people who wear it.

An important part of this diversity is customer’s gender: men have different tastes than women. That concept watch mentioned above looks fantastic—if you’re a male. I can’t imagine my wife wearing it.

Then there’s the question of size: as someone who’s 6’7″ tall, I know firsthand that “one size fits all” is the greatest lie ever told by clothing manufacturers. Since everyone’s body is unique, wearable devices must also consider comfort and fit in the design.

Apple may be able to use something like an iPhone case to make a wearable device appeal to both sexes. Or adjustments that make a single device (SKU) adapt to multiple body shapes. But I suspect that it’s going to take more than that to be appealing as a piece of fashion.

The Customer

Now that we’ve looked at the challenges in developing these devices, let’s think about the most important question Apple is asking itself:

Who is going to buy this wearable technology?

Trends are always set by the younger generation. Especially with clothing, jewelry and other items that appeal to a demographic with a lot of expendable income. To me, this quote by Tim Cook is the most telling:

“To convince people they have to wear something, it has to be incredible. If we asked a room of 20-year olds to stand up if they’re wearing a watch, I don’t think anyone would stand up.”

This response to Kara Swisher’s question about Apple’s interests in wearable technology covers all the bases. It includes the target market (“20-year-olds”), product focus (“has to be incredible”), and most importantly, he’s seeing the same thing I am: people don’t need to wear watches because they already have that computer in their pocket.

Note also that in the response he doesn’t say “wear a watch”, it’s “wear something”. It’s implied, but not stated. Remember that he learned from the master of misdirection: Steve Jobs.

The Product

Given everything presented above, it’s pretty clear to me that a “smartwatch” isn’t in Apple’s immediate future. But they’re clearly interested in wearable technology. So what are the alternatives for a product that could be released this year?

The first step is to start looking at things from Apple’s point-of-view. I ask myself, “What problems can a wearable device solve?”

As I think about answers to that question, it leads me to the conclusion that Jony Ive and crew aren’t looking solely at the wrist. Wearable technology could take cues from other kinds of jewelry: rings and necklaces, for example.

What if Apple’s entry into this space is a ring?

  • Limited display — A discreet way to provide notifications—just an LED or two that indicate what’s happening on your iPhone. Maybe even a small, flexible E Ink display for high contrast text.
  • Tactile — A way for your finger to sense a notification. It’s easy to miss audio cues in a noisy room or a vibration in your pocket.
  • Small & light — A hallmark of Apple design. Simplicity in form and function.
  • Customer appeal — Those 20-year-olds don’t wear watches, but jewelry is already a part of their culture. “Bling” came from the world of hip hop.
  • Sensors — Your finger has a pulse and blood pressure for Healthbook.
  • Power — The Lightning connector is small for a reason.
  • Competition — While all its competitors are rushing watches to market, Apple catches them with their pants down.
  • Low cost — How many of these rings could Apple sell if they were priced at $99?

But the biggest feature of all would be that this wearable device could support iBeacon. This technology is based on Bluetooth LE which Apple describes as “a new class of low-powered, low-cost transmitters that can notify nearby iOS 7 devices of their presence.”

Let this sink in for a second: your wearable device is transmitting a signal with a unique identifier that can be picked up by an iOS 7 device. And the proximity detection is sensitive within a few inches. Presumably, this signal could be also be detected on your Mac as well, since they have supported Bluetooth 4.0 since mid-2011.

By wearing this ring on your finger, your devices can know how close you are to them.

This opens up a world of possibilities: imagine the joy we’d all feel when a notification only popped up on the device we’re closest to. Right now my ring finger is hovering over my MacBook Air’s keyboard by 2-3 inches, while the phone in my pocket is over a foot away. Notification Center needs this information.


Predicting Apple’s future is always fraught with difficulties. I may not be right about the end result being something other than a watch, but I’m certain that there are people at Apple thinking about the issues I’ve outlined above.

And I, like many others, am really looking forward to wearing Apple.

Font Points and the Web

When sizing fonts with CSS, there’s a rule of thumb that states:

1em = 12pt = 16px = 100%

There are even handy tools that help you calculate sizes based on this rule.

But this rule of thumb leaves out a very important piece of information. And without that information, you could be left wondering why the size of your type doesn’t look right.

Testing Points and Ems

To illustrate, let’s take a look at some work I’ve been doing recently to measure text accurately on the web. I have a simple test page that displays text in a single font at various sizes:

<!DOCTYPE html>
<html lang="en">
  <meta charset="utf-8" />
  <title>Em Test</title>
  <meta name="generator" content="BBEdit 10.5" />
    body {
      font-family: "Helvetica Neue", sans-serif;
      font-size: 100%;
      line-height: 1;
    p {
      padding: 0;
      margin: 16px 0 16px 0;

<p style="font-size: 2em; background-color: #eee;">MjṎ @ 24pt / 2em</p>


You can view a slightly more complex version of the page here.

The W3C recommends specifying fonts using either ems or pixels. Since high resolution displays are becoming ever more common, that really leaves you with just one choice: the em.

(Note: In the examples that follow, I’m using text set at 2em since it’s easier to see the problem I’m going to describe. The effect, however, will happen with any em setting.)

The body is set in Helvetica Neue at 100% so 1em will be the equivalent of 16px when the user’s browser is using a default zoom setting. The line-height is 1 so there’s no additional padding around the text: the default of “normal” would make the line approximately 20% taller.

When you display the test page, everything looks good because the sizes are all scaled correctly relative to each other. A quick check of the light gray background with xScope shows that the height of the paragraph element is 32 pixels (2 ems):


But then things got confusing.

Points aren’t Points

I had just been measuring some text in TextEdit and noticed something was amiss. Comparing the two “24 point” fonts looked like this:

TextEdit versus Browser

I’m no typography expert, but there’s something clearly wrong here: a 24pt font in TextEdit was noticeably smaller than the same size in my web browser.

I confirmed this behavior in three browsers running on my Mac: Safari/Chrome (rendering with WebKit) and Firefox (rendering with Gecko) displayed the larger version of 24 point text. Why were the sizes different?

After some experimentation, it appeared that rendered glyphs were from a 32pt font:

72 DPI

What the hell?

A Brief History of Type

When confronted with a problem like this, it’s always a good idea to question your assumptions. Was I measuring the right thing? So I started learning more about type…

In general, points are meaningless. It’s a relic of the days of metal type where the size specified the height of the metal, not the mark it made on the page. Many people mistake the size of a glyph (shown below with red bars) with the size of a point (green bars):

Point versus Glyph

(Photo by Daniel Ullrich. Modifications by yours truly.)

Even things like the word “Em” got lost in translation when moving to the web: it originally referred to the width of a typeface at a given point size. This worked in the early days of printing because the metal castings for the letter “M” were square. Thankfully, we’re no longer working in the 16th century.

In modern fonts, like Helvetica Neue, a glyph for a capital “M” may be square, but the flexibility of digital type means that the width and height of a point rarely match.

Thanks Microsoft!

After doing this research, I was sure I was measuring the right thing. The sizes of the glyphs should match, regardless of point size. Something else was clearly in play here.

Let’s just say I spent a lot of quality time with Google before eventually stumbling across a hint on Microsoft’s developer site. The document talks about using a default setting of 96 DPI. I’ve been spending a lot of time lately with the Mac’s text system, so I knew that TextEdit was using 72 DPI to render text.

I quickly opened a new Photoshop document and set the resolution to 96 pixels per inch (DPI). And guess what?

96 DPI

All the text got larger and it matched what I saw in my browser. Mystery solved!

72 DPI on the Mac is 75% smaller than 96 DPI used by the Web. So the 24pt font I was seeing in TextEdit was 75% smaller than the 32pt font used in the browser.

Further research about how 96 DPI is used on the web turned up this Surfin’ Safari post on CSS units written by Dave Hyatt back in 2006:

This is why browsers use the 96 dpi rule when deciding how all of the absolute units relate to the CSS pixel. When evaluating the size of absolute units like pt browsers simply assume that the device is running at 96 CSS pixels per inch. This means that a pt ends up being 1.33 CSS pixels, since 96/72 = 1.33. You can’t actually use the physical DPI of the device because it could make the Web site look horribly wrong.

That’s another way to think about this problem: a single point of text on your Mac will be 1.33 times larger in your browser.

Now What?

Now that we know what caused the problem, how can we avoid it?

The key piece of information that’s missing in the “1em = 12pt = 16px = 100%” rule is resolution. If you’re specifying point sizes without also specifying resolution, you can end up with widely varying results. For example, each of these is “24 points tall”:


If you’re lucky enough to have a Retina Display on your Mac, you’ll be rendering text at 144 DPI (2 × 72 DPI). That’s 20% larger than the last example above (Windows’ 120 DPI setting.) Display resolution is increasing and so are the number of pixels needed to represent “a point”.

Note that you can’t “fix” this problem by specifying sizes in pixels. If you specify a font size of 16px, your browser will still treat that as 12pt and display it accordingly.

As a designer or developer, you’ll want to make sure that any layout you’re doing for the web takes these size differences into account. Some apps, like Photoshop, allow you to specify the resolution of a document (that’s how I performed my sizing tests.) Make sure it’s set to 96 DPI. Resolution may not matter for exporting images from Photoshop, but it will make a difference in the size of the text in your design comps.

Most other Mac apps will rely on Cocoa’s text system to render text, so if there’s no setting to change the document’s resolution, a default of 72 DPI should be assumed.

An alternative that would suck is to start doing your design and development work on Windows where the default is 96 DPI. That setting also explains why web browsers use this resolution: remember when Internet Explorer had huge market share?

And finally, expect some exciting new features for measuring, inspecting and testing text in your favorite tool for design and development. I’m doing all this precise measurement for a reason :-)

Updated February 25, 2014: It turns out Todd Fahrner first identified this problem back in the late 1990′s. His work with the W3C was instrumental in standardizing on 96 DPI. What’s depressing is that I knew about this work: Jeffrey Zeldman and I even developed the Photoshop filters mentioned on his site. Maybe I should send in my AARP membership form now.

Counting Beans with AppViz 3

In my last post about AppViz, I mentioned that I spent about six months creating an internal accounting tool called BeanCounter. Why the hell did I do that?

Because I don’t want to run my business on financial guesses based on iTunes Connect sales reports.

The Need For Financial Accuracy

For many app developers and iBook publishers, income from iTunes Connect is a significant part of the business’ financial statement. In many cases, the App Store is a developer’s only distribution channel, so it’s responsible for 100% of gross revenue.

When you have a financial statement, you want it to be exact. If your local tax collector comes calling and you show them guestimates, you’re in for a rude awakening. You’ve got a paper trail that’s fishy and that’s going to invite closer scrutiny. It’s the reason every piece of accounting software ever written has a reconciliation feature.

Publishers pay author royalties and many app developers split revenue with a designer. When it comes time to share the monthly Apple ACH deposit, financial guesses are also a problem. Not only will you be giving your partners the wrong amount of money, you’ll eventually be reporting it incorrectly on a 1099-MISC. Your estimated payments can be off by thousands of dollars:

Sales Reports Are Not Accurate

The root of the problem is that all services except AppViz 3 use fluctuating values like fiscal calendar ending dates, payment clearing dates, and currency exchange rates. If you do, you’re making financial guesses.

Don’t take my word for it, here’s what App Annie has to say:

Why do my sales reports in App Annie not exactly match my financial reports in iTunes Connect?

App Annie fetches the sales data from the iTunes Connect “Sales and Trends” section. There are a few reasons why the sales data doesn’t match Apple’s “Financial Reports” and the amount of money you receive from Apple.

Fiscal calendar. Apple uses fiscal months rather than calendar months for payouts. To see Apple’s fiscal calendar, go to “Payments and Financial Reports” and click the “Fiscal Calendar” link. For example, fiscal March 2011 starts on Feb. 27 and ends on Mar. 26.

Clearing of payments. What matters in the case of financial reports is what payments were made during a fiscal month, not how many downloads were made. Since most people use credit cards to buy apps, it can take up to 2-3 days for a payment to go through. Also, some payments never go through!

Currency conversions. Apple’s “Financial Reports” use Apple’s own currency rates, whereas App Annie always uses today’s exchange rate.

Remember that the last two points above have a certain degree of unpredictability, which makes the figures we get from Apple’s “Sales and Trends” slightly different from the figures in Apple’s “Financial Reports”.

That last item is particularly bad: currency fluctuations will give you wildly inaccurate accounting. For example, let’s say you sold €10,000 of product and used the rate on October 28th, 2013 (1.38) to convert that amount to $13,800. Then, Apple deposited $13,400 into your account on November 7th using that day’s 1.34 rate. Hope you didn’t pay your partners using that financial guestimate of $13,800!

The bottom line is this: you cannot rely on estimates in Sales Reports when doing financial reconciliation or partner payouts. Only Financial Reports can be used for this purpose.

Financial Calculations Are Hard

The problem is compounded when you have multiple products with different partners. Figuring out how to divvy up the money turns out to be a hard problem and it’s why everyone else has punted on doing it right. It’s also a competitive advantage for us, so I’m not going to go into any details about how we get the numbers to come out right.

I will, however, give you a peek into the first hurdle you’ll encounter: you can’t use floating point values for financial calculations. If you write code like this, you’ll be in for a world of hurt as errors accumulate:

double subtotal = balanceTotal + 
    (salesTotal + adjustments);
if (subtotal != 0.0) { // is 0.00000001 a zero value?
  rate = deposit / subtotal;

Cocoa has an awesome subclass of NSNumber called NSDecimalNumber. Classes like NSDecimalNumber are one of the reasons that “NeXTSTEP had a long history in the financial programming community.”

When using NSDecimalNumber your code will get more verbose than the snippet above. But more importantly, it will now be exact:

NSDecimalNumber *subtotal = [balanceTotal
if ([subtotal compare:[NSDecimalNumber zero]]
    != NSOrderedSame) {
  rate = [deposit decimalNumberByDividingBy:subtotal];

It also forces you to think about problems like rounding: do you want to use NSRoundBankers when your code calls -decimalNumberByRoundingAccordingToBehavior:?


I hope you now see why I thought it was wise to spend a lot of time coming up with a system that ensures financial accuracy. I’m also thrilled that this system is now a part of AppViz 3, the app that’s been keeping track of our products on iTunes Connect since the App Store first opened in June 2008.

It also makes me happy that other developers are seeing the same benefits for accurate financial reconciliation. Helping other developers is what makes me tick.

Take a moment to think about how these issues affect your own business and then take a look at AppViz 3. I think your balance sheet, your partners and the tax man will be happy you did.

iPad Not Annoying

In Mavericks, there’s a new notification that reminds users an iPad isn’t charging:


As iOS developers, we spend a lot of time plugging and unplugging devices each day. After you’ve seen this reminder a few dozen times it becomes more annoying than helpful.

So I complained about it on Twitter. And thanks to a pointer by Paul Haddad, I had a hint on how to get what I wanted.

After checking that /usr/libexec/usbd contained the “NoiPadNotifications” string and looking over the usbd manual page, I gave it a shot:

$ sudo defaults write com.apple.usbd NoiPadNotifications \
  -bool YES
$ sudo killall usbd

The next time you plug the device in, the usbd daemon will be started by launchd, but you won’t see any notification. If you change your mind at a later date, just undo the change with:

$ sudo defaults delete com.apple.usbd NoiPadNotifications