Learning SwiftUI

Ok, I admit it. I’m a bit late in going through Apple’s tutorial on SwiftUI. That has had its good points–SwiftUI is amazing!!!–and its bad–much changes between Xcode5 beta updates. I will update this post regularly with some of the gotchas that I’ve found between the latest Xcode5 beta and the Apple SwiftUI tutorial. I hope this helps.

Working With UI Controls

In ProfileEditor.swift,

Picker("Seasonal Photo", selection: $profile.seasonalPhoto { ForEach(Profile.Season.allCases.identified(by: \.self)) { season in Text(season.rawValue).tag(season)

To avoid the error,

Value of type '[Profile.Season]' has no member 'identified'

ForEach() should be written as,

Picker("Seasonal Photo", selection: $profile.seasonalPhoto) { ForEach(Profile.Season.allCases, id: \.self) { season in Text(season.rawValue).tag(season)

Why I Love Swift: Functional Programming

Apple’s Swift language, which is not even a year old, has grown on me in ways I would never have expected. Partly, that’s because it has opened my eyes to ways of programming I was unaware of.

One of the programming paradigms that Swift forced me to at least look at was functional programming. What’s functional programming? Well, here’s a post by Guanshan Liu, Functional Programming in Swift, that does a much better job than I could ever do. And there’s a great book, Functional Programming in Swift. Simply put, functional programming allows functions to be used as parameters within a function call. Is that very useful or just another egg-head, ivory-tower CompSci methodology that no app developer really needs? Hardly.

Let’s say within a HomeKit app I’m creating that I have an array of accessories (home-automation devices) and their services. Now, that and a nickel won’t get me a cup of coffee nor do much for any user of my HomeKit app. So I want to use the list of the services’ serviceType, mind you in the same order as Apple’s service types supported by HomeKit’s Accessory profile, and the devices that have those service types. Hmmm… More…

Austin vs Silicon Valley

Note: This post was originally written by Zac Sweers on Quara in response to the question, What is Austin like for startups and tech companies? How does it compare to Silicon Valley?“. Zac does the best job I’ve yet read of distilling the issues facing Austin and the growth of its tech business.

There are two big issues that startups in Austin face that I think stunt their collective growth. This is based on my time there (5 years of college), interning a short time at a local start up, having a few friends found local startups, and just general observations of the startup community. I now live in Palo Alto, CA working at a startup called Flipboard. More…

Xcode Issues: How To Work-Around An Ineligible iOS Device

There may come a day, a sad day, when you install the latest version of Xcode, plug-in you iOS device, wait for it to appear in the list of scheme supported devices, and…nothing. Then you click on the scheme pull-down menu and see the following,

Xcode Ineligible Device Post 03 15 2015 Img 1

How did your iOS device become ineligible for development? Well, I don’t know and nobody else seems to have an answer. But there is a work-around More…

The (Obvious) Importance Of Customer Convenience

There’s a discussion over at the Pebble forums about whether a user should be able to manage multiple Pebble watches in the Pebble app for iPhone or Android.


Why manage switching between multiple Pebbles from the Pebble app? Well, for one, it’s a better user experience.

Most customers wanting to do anything with their one Pebble, or many Pebbles, will naturally go to the Pebble app. That should be embraced.

The Pebble app should be the single place for all things Pebble. Doing that affirms a positive user, and therefore brand, experience and keeps the user focused on Pebble. Having an app that allows customers to manage multiple Pebbles in an easy way will also encourage them to buy more Pebble products.

If managing another Pebble becomes a hassle, then Pebble potentially looses additional sales to a current customer. Worse, that now less-than-satisfied customer means it’s less likely Pebble sells to others who read or hear that the app isn’t that convenient.

Anecdotally, think where the iTunes ecosystem would be if you couldn’t manage multiple iPods, iPhones, etc. within the iTunes app. The answer is, not the dominant position it is in today.

Xcode 5 Notes

Some migrating their iOS projects over to Xcode 5 but not converting their project’s xib(s) or storyboard(s) might notice that the performance of Xcode drops when trying to edit those files. Looking in Activity Viewer, it isn’t Xcode that is taking-up all the cycles, but a tool, Interface Builder Cocoa Touch, that has now gone from using its normal smidgen percentage of CPU to over 60%! This will make editing a storyboard or xib very painful.

A search of “Interface Builder Cocoa Touch” will not result in links that address this is issue. After all, Xcode 5 has only been publicly available since today. So what to do?

The problem is the Interface Builder Document settings for the iPhone Storyboard or xib in which the performance is laggy.

Start by looking in the File Inspector of each storyboard in which the performance problem exists. It is likely that the storyboard Interface Builder Document setting was set for “Xcode 4.6”. That is, as it turns-out, bad. Changing the IB Default Document setting of the xib or storyboard to “Default Xcode 5” will fix the problem. Once you make that change, the Interface Builder Cocoa Touch tool will return to its sipping of only a few threads and using 0.0% of the CPU.

VC Funding–SiValley vs. Texas

After reading an article in the New York Times about how music acts as a possible attractant to start-up’s, I wanted to get some numbers to see if that were true. From a historical basis, it’s important to remember that in 1999 Texas was doing nearly 10% of the venture funding of Silicon Valley, of as I call it, SiValley (cute, huh?).

2012 VC Funding

Year SiValley Texas Austin
2012 $10,968 $934 $621
% of SiValley 100% 6.2% 5.7%
2012 VC Funding Stage SiValley Texas % of SiValley
Seed $316 $2 0.6%
Early-Stage $3,279 $180 5.5%
Expansion $4,570 $344 7.5%
Later Stage $2,802 $408 14.6%

Source: PricewaterhouseCooper MoneyTree Survey

GLKit – Transforming A Vector With A Quaternion

OpenGL 3d axes

Since I haven’t seen this on Stackoverflow, the following is a method to transform a vector (GLKVector3) based on an attitude quaternion (GLKQuaternion).

First, assume that you have a GLKVector3 as input, call it inputVector3. inputVector3 could be yaw, pitch, and roll influences from an aircraft’s control surfaces or thruster output on a spacecraft. You know your vehicle’s attitude and have calculated that attitude into a quaternion. So, the goal is to have the inputVector3 transformed into an ivar, say GLKVector3 deltaV, that is in terms of the vehicle’s attitude.

- (GLKVector3)transformVector3:(GLKVector3)inputVector3 withAttitudeQuaternion:(GLKQuaternion)attitudeQuaternion
GLKVector3 deltaV = inputVector3;

//Always ensure that your attitude quaternion has been normalized
attitudeQuaternion = GLKQuaternionNormalize(attitudeQuaternion);

//Convert the normalized attitude quaternion into a GLKMatrix3.
GLKMatrix3 tempQMatrix3 = GLKMatrix3MakeWithQuaternion(attitudeQuaternion);

//Since v' = v T, where T is a transform matrix, multiply
//the attitudeQuaternion GLKMatrix3 with the necessary GLKVector3.
deltaV = GLKMatrix3MultiplyVector3(tempQM3, deltaV);

return deltaV;

@WWDC 2013

Good morning! So, here I am at WWDC 2013. I’ve had some coffee and a muffin compliments of Apple, and am now cooling my heels on the second floor. This is much better than in years past when they’d let us chill-out in the nice SF fog…until 9:55 after which we’d literally run to find a seat.