2
Dec
2014
 

Beginning iOS Development With Swift

by Matt Long

Many years ago now, I wrote a tutorial for the beginner to learn how to use outlets and actions as this is often one of the least familiar aspects for new developers who are wanting to learn iOS. It’s simple once you’ve seen it, but until then, there’s a gap. This time around I’m presenting an application that is similar to the one I did back then, however, it’s up to date with Xcode 6 and Swift. If you are new to iOS development, this should help get you going.

Beginning iOS Application Development with Swift from Skye Road Systems on Vimeo.

 
5
Nov
2014
 

Swift and valueForKeyPath: You Can’t Keep A Good API Down!

by Matt Long


tl;dr; Download the Value For Key Path Playground


I was incredibly disappointed in Swift when I started to look into how key value coding might be preserved in the transition from Objective-C. Of course, Apple would preserve that, right? And I don’t mean by resorting to using Foundation classes–you know all type-casty and everything (yeah, type-casty). Are we progressing forward or looking to the past, after all? I shouldn’t have to rely on NSArray like this:

Right? Who wants to do that? What’s the proper Swift way?

Well, my early assumption from what I was seeing in Swift was that valueForKeyPath: was gone and no longer did we have a convenient way to grab only the fields we needed from a collection of objects. It appeared that it couldn’t be done–at least not in any idiomatic elegant way. Then I downloaded some sample code from the Apple developer site and noticed they were doing what I needed, but using map to do it. The answer was map. Here’s an example:

Now the lastNames variable contains a list of strings with just the last name property of my items array. Given an array of dictionaries like this, you can see how that is providing pretty much what we used to get from valueForKeyPath:

lastNames now contains:

Notice we also have an address property that points to a dictionary. If want to get the street property inside of address, we can drill down the same way:

Now, you can see we had to force-unwrap the address property in order to access the street property. This works perfectly and is a fine replacement for valueForKeyPath: of old. When the call succeeds we now have all of the street addresses in the streetAddresses array:

Take a look at the Value For Key Path Playground if you want to see it in action.

What About Safety?

In Objective-C, if you message nil, it’s a no-op. In Swift, however, if we unwrap an optional that is nil, we will crash. So, on this line:

when we unwrap using the bang ! operator, if that value doesn’t exist, we’re in trouble. Say our data was changed to this:

Notice the address field has been changed to addr. This causes a crash.

Playground Crash

Meanwhile, with the old Foundation way, we do this:

but look what the output is. NSNull!

No crash. So which is better?

Well, if your data can be unpredictable, which really shouldn’t happen, then the Foundation outcome is “safer” from a crash perspective. However, your data should be nailed down, so a crash would actually tell you what’s wrong with your data pretty quickly.

What, though, is the safe Swift way of handling this? We can coerce our objects to optionals and use optional chaining instead:

So our first optional operator says to return the object or nil and the second operator says that is should be an optional of type String. This call returns an array of optionals that has this output in our playground:

Assuming the following data:

Notice the first two use the bad addr field and the last two use the correct address field.

For my applications, I think I would prefer to see a crash so I know my data is bad. It’s the server developer’s problem. Am I right? ;-)

Taking Map() Farther

The map() function really goes far beyond this trivial little valueForKeyPath: replacement example. You can really massage your data into any form you want with it. Say for example you wanted to create an transformed array of dictionaries from your array of dictionaries that had some of the same data, but organized differently. For example:

This returns an array of dictionaries that contain a single key value pair with a key called full_name and value of the first name and last name of each item in the original array concatenated together. The output looks like this in our playground:

As you can see, there really are a lot of possibilities for massaging your data structures using map. The tough part is imagining how it might be used and often that just comes from experience. The more you use it, the more obvious the solutions will become.

Swift Is Not So Bad

There are certain complaints about Swift I still have, however, I am finding that it is growing on me. I am starting to have much more success making my code pure Swift–pulling back from my old habits and considering how problems should be solved in this brave new Swift world. It’s getting better and some of the language aspects are actually better than Objective-C. I couldn’t see that forest for the trees just a couple short months ago. Until next time.

 
29
Oct
2014
 

Protocols in Swift With Core Data

by Matt Long

Sometimes you have a set of objects you want to display in the same form–say, for example, in a table view controller. What if those objects have, by design, nothing in common and nothing to do with each other? This is a case where you can create and conform to a protocol–known in some languages as an interface–to provide a simple way to have each class type provide a display name that can be displayed in your table view controller.

Recently while using this language feature writing Swift code, I ran into a few snags and learned from the process. I figured I would document it in this screencast. It walks you all the way through from project creation, so it’s about 35 minutes.

Here’s what you will learn:

  • How to setup CoreData entities in the data model
  • How to add a run script action to build your managed object classes using mogenerator
  • How to create a protocol in Xcode 6
  • How to implement a protocol in the various managed object classes
  • How to preload your CoreData store with test objects in code
  • How to load each object type generically into a table view controller

And if you want to just cut to the chase, grab the code from github.

Protocols in Swift With Core Data from Skye Road Systems on Vimeo.

 
8
Jun
2014
 

The Core Data stack in Swift

by Marcus Zarra

swift-heroWhenever Apple releases a new version of Xcode one of the first things that I do is look at the default templates and see if there are any new or interesting things.

This year, with the release of Swift, there are some pretty radical changes. Yet the Core Data stack initialization code is still the same.

There is nothing wrong with the default template code but there isn’t really anything right about it either. It is far better than it once was but it is still overly verbose and hard to follow.

Therefore, I present my Swift Core Data stack code that I will be using as I grok this language.

(more…)

 
25
Feb
2014
 

Deleting Objects in Core Data

by Marcus Zarra

I very rarely speak out against another blog post. I find the resulting argument back and forth draining. However, there are exceptions and one occurred over the weekend.

Brent Simmons has been blogging about his conversion of Vesper to a Core Data application. A recent post of his titled Core Data and Deleting Objects set my teeth on edge. Brent says:

“The best advice I’ve heard about deleting managed objects is to 1) not do it, or 2) do it only at startup, before any references to those to-be-deleted objects can be made.”

I do not know who is giving Brent advice but he must be playing tricks with him or just trying to wind him up. The advice was simple; don’t delete Core Data objects or if you are going to delete them, delete them at launch.

Will that work? Sure. Is it the right answer? Not even close.

(more…)

 
1
Jan
2014
 

Fetched Properties; useful?

by Marcus Zarra

Core Data has a number of features and abilities that are not commonly used. Chief among those are fetched properties. In discussing them with a number of developers, most have never heard of them and those who have heard of them couldn’t come up with a viable use case for them.

To be honest, I don’t have a lot of use cases for them myself. They are definitely not one of the core features of Core Data that I recommend people learning when they are initially getting comfortable with the framework.

In this article we will discuss one use case for fetched properties and the impacts.

## The Use Case

The use case for fetched properties that I have run across a few times comes into play when you have more than one persistent store file on disk. Imagine you are building a recipe application (one of my favorite examples). You decide to include a pre-built read-only database with existing recipes. However, your application has the ability to add notes and social comments to a recipe.

You want to keep the recipe database as read only (you have a separate one for new recipes) but you want the user to be able to add comments. Where do we put the data?

In this contrived situation, storing the comments (and other metadata) in another store makes sense. Unfortunately we can’t have relationships across physically separate stores.

Enter the Fetched Property.

## Fetched Property

A fetched property is a property added to a NSManagedObject entity that instead of storing a value or a relationship, it stores a NSFetchRequest. When the property is accessed for the first time the NSFetchRequest is fired and the results are returned.

A fetched property always returns a NSArray (well a subclass but that is a minor detail) and it can be configured to sort the results.

Unfortunately, the editor in Xcode does not permit adding sort criteria so the only way to add a sort to a fetched property is to create the fetched property in code. Hopefully that will be corrected in some future release of Xcode.

What does a fetched property look like? In the Core Data model editor, a fetched property is added just like an attribute or a relationship. Then in the Data Model inspector you can configure the NSFetchRequest.

A Fetched Property shown in Xcode's data modeler

A Fetched Property shown in Xcode’s data modeler

The Destination is the entity that will be returned by the fetched property. The predicate is a string representation of the NSPredicate configured within the NSFetchRequest.

Further, the predicate can use one of two variables to help configure it:

$FETCH_SOURCE gets replaced by a reference to the entity that owns the fetched property. By using this variable we can reference properties in the owning entity.

$FETCHED_PROPERTY gets replaced by a reference to the the property description of the fetched property. The property description includes key value pairs that are accessible from within the predicate. I have not run across a situation where I have used this variable.

## The sharp edges

There are unfortunately some concerns with fetched properties.

Unlike a relationship, there is no way to pre-fetch a fetched property. Therefore, if you are going to fetch a large number of entities and then desire to access the fetched property for those properties, they are going to be fetched individually. This will drastically impact performance.

Fetched Properties are only fetched once per context without a reset. This means that if you add other objects that would qualify for the fetched property after the property has been fetched then they won’t be included if you call the fetched property again. To *reset* the fetched property requires a call to -refreshObject:mergeChanges:.

A fetched property always returns an array. While this is not a major issue if in fact you want more than one object returned. However, when that is not the case it is an additional method call that you need to make every time or add a convenience method. More code equals more bugs.

## To use or not to use

Fetched properties are not a main line piece of Core Data. It appears that even the Core Data team (or the Xcode team at least) agrees with that assessment based on how little effort is given to them in the model editor. Should you use them?

It depends. If you are joining two separate persistent stores and need a *soft* relationship between entities in those stores then yes, you can use them. They do work.

Be mindful of the edges, they are sharp.

 
17
Dec
2013
 

Automating OS X app test build distribution across multiple OS versions

by Fraser Hess

With Apple now shipping OS X upgrades every 12-15 months, Mac developers are very quickly finding themselves supporting their apps on multiple OS X versions. Until recently, my approach to testing on multiple OS X versions involved partitioning an external USB drive and installing the OS X versions onto it and booting off the partitions to test.

While this approach is inexpensive, the test-discover-reboot-fix-build-test cycle just got to be too much for even this frugal Scot.

Enter the Mac mini

My new solution has 2 parts: a maxed out Mac mini with VMware Fusion to support all the targeted OS X versions and a scripted piece that will sync new test builds to the VMs.

The current $799 Mac mini has a quad-core Intel Core i7, a 1TB HD and is expandable to 16GB of RAM. Our local MicroCenter had a $749 sale on that model so I picked one up along with a 16GB RAM upgrade. After I setup 4 VMs, one for each of 10.6 – 10.9, I found the performance to be incredibly slow. Analyzing the issue quickly identified the speed of the stock HD as a bottleneck, so after considering returning the whole kit for a BTO Fusion Drive model, I picked up an OWC 240GB Mercury EXTREME™ Pro 6G SSD, and now the performance is great. (Installing an extra HD in a Mac mini is possible, but if you do, make sure you watch and understand the videos on the topic and make sure you order the correct parts to install in your Mac mini.)

Moving the builds around

Each of my Mac Xcode projects now has an extra scheme called MyApp test build. The following scheme settings are used: In Run MyApp.app, I’m using the Release build configuration and I’ve set Launch to Wait for MyApp.app to launch since I don’t intend to run these builds from Xcode. Most importantly, in Build->Post Actions, I’ve added a Run Script Action with Provide build settings from set to the app. The script below creates a new uniquely-named folder in the $root_destination_folder every time you build and will copy the resulting product into that newly created folder. The folder name combines date/time, product name, and the current git describe. The $root_destination_folder should be in a folder that is synced by a service. I used Dropbox at first, but it doesn’t seem optimized for the large number of small files that compose a Mac application bundle, even with LAN syncing turned on. I’m now using BitTorrent Sync, which uses the BitTorrent protocol. Even as a beta release, I had great success with it. By adding the shared folder to the BitTorrent Sync client on each test VM, every time I make a test build, it automatically appears on each VM.

By running multiple OS X versions in VMs simultaneously and syncing test builds, I’ve nearly eliminated all the waiting involved in testing and iterating across multiple OS X versions.

Note 1: For testing on Mac OS X 10.6 Snow Leopard, only Snow Leopard Server is supported in VMware Fusion. Apple has made Snow Leopard Server available to paid Mac developers as a free download. The provided serial number expires at the end of 2014.

 
10
Dec
2013
 

Using GIT In Xcode

by Joe Keeley

Git has become a very popular version control system in iOS and Mac development. Git comes with a set of command line tools to check status, commit changes, view logs, make and merge branches, and coordinate commits with a remote repository.  There are a number of desktop apps that can perform these functions, including Xcode.  When I ask other iOS and Mac developers how they interact with Git, most say they use the command line or a separate desktop app like Tower.  I find very few developers use Xcode for even some basic Git tasks, and many developers are not aware of the Git support Xcode offers.

For my own workflow, I like to minimize the number of tools used and number of switches between apps needed to complete a task.  So, I decided to attempt to use Xcode exclusively to interact with Git and share my results.  So far I have been pleasantly surprised at what all Xcode can do with Git. If you have not taken a look at Xcode’s support for Git, you may be surprised how much you can accomplish.

This article assumes basic familiarity with Xcode and Git, and describes Git functionality present in Xcode version 4.6.2. (more…)

 
20
May
2013
 

Creating A Happy Appy Song

by Matt Long

App developers need ways to promote their apps and audio and video provide a way to do that. At a recent iOS developer camp in Colorado I gave a talk in which I demonstrated some ways developers can create their own creative content like audio and video in-house. In one segment I demonstrated a technique that I refer to as creating a Happy Appy Song. What is it, you ask. You’ve heard it. It’s a happy sounding fanciful tune that plays in the background as some narrator describes the wonders and benefits of an app (or other product for that matter). The basic premise of the happy appy song is that, first of all, it’s easy to create, but second there’s a simple formula. Here is all you need:

1. A happy chord progression in a major key
2. A simple drumbeat
3. A glockenspiel sound

And now I present to you, Creating a Happy Appy Song

[ylwm_vimeo height=”400″ width=”600″]66576979[/ylwm_vimeo]

 
26
Apr
2013
 

iOS Crash Logs On iCloud Synced Devices

by Matt Long

I tweeted a call for help today to figure out how to get crash logs from a device that syncs with iCloud rather than with iTunes and a cable. The issue is that you can only sync with one and not both and switching between them willy nilly can be perilous unless you enjoy losing your data just for the fun of it.

Several responses suggested taking things into my own hands by rolling my own logging mechanism when building an app I intend to ship. I think this is likely the approach I will take in the future, however, it doesn’t help my immediate problem. How do I get crash logs from an app I already shipped that is running on client’s device not physically located near me? Here’s a summary of what people suggested. Drill down in the settings app and copy the contents of the crash log like this (click/tap to enlarge):

Crash Logs Drilldown

Then, paste that into an email:

Paste In Email

Then you can send the crash log to any email address you specify.

It certainly is not a pretty approach, but it will get the job done.

Thanks to the folks who responded to my call for help, @davidiom, @therealkerni, @thenighttrader, and @rckoenes. I appreciate it!

 
3
Apr
2013
 

StackOverflow Reputation As A Hiring Metric

by Matt Long

I’ve been using StackOverflow nearly since it started back in 2008. I remember when it first started there didn’t seem to be much going on and so I forgot about it for a time. Then, one day, while searching the interwebs for an answer to a programming question, SO was the first hit in my search results. At that point I went back and started using it regularly–not only to find answers, but to offer my own experiences and expertise to help others. It’s a great site and I have nothing but high praise for its founders, Jeff Atwood and Joel Spolsky. The entire StackExchange network is an impressive engineering achievement. (more…)

 
18
Mar
2013
 

Anonymous Image File Upload in iOS With Imgur

by Matt Long

It seems like a pretty useful feature, anonymous image file upload in iOS with imgur. If you need to upload images and don’t want to fool with some authentication mess like OAuth this technique is perfect. There are libraries that have simplified the OAuth process, however, it’s nice to be able to just initiate an upload, get a result URL back and be on your way. No fuss, no muss. That’s what I was looking for, so I wrote a little app that demonstrates how to do exactly that.
(more…)

 
5
Feb
2013
 

Querying Objective-C Data Collections

by Matt Long

In my Xcode LLDB Tutorial, I mention using the debugger to interrogate data collections. Well, I wanted to elaborate on that idea a little because there are some techniques you can use for querying objective-c data collections that are very powerful.

If you develop apps for clients, you my be one of the lucky ones–the ones who actually get to model your data and use Core Data to store and access it. But I’m betting there are many of you who aren’t the lucky ones–or at least not on all of your projects. From time to time you have to deal with data in whatever format your client gives it to you. Maybe you’ve even suggested taking the CSVs or Plists (or whatever other formats clients have come up with to ruin your life) and actually loading those into Core Data. But they don’t get Core Data and they shoot down the idea. Well, you may want to just walk away from the gig. However, if you’re like me, you’ve got bills to pay and clients (the good ones at least) tend to help you accomplish that. Well, fortunately for us, Objective-C makes dealing with this kind of data manageable using a little technique known as KVC, Key-Value-Coding, with array filtering and sorting.

This is not an advanced topic, so if you’re already familiar with how KVC and array filtering and sorting works, this post may not help you as much. But for those of you who are fairly new to iOS development, you need to know about this magical feature of the language as all the senior iOS developers use it and you should too. (more…)

 
29
Jan
2013
 

Down with Magic Strings!

by Patrick Hughes

Developing iOS apps in Xcode is pretty great. With Objective-C and llvm we get type checking and autocompletion of all our classes and method names which is a nice improvement over my favorite dynamic languages. Unfortunately there are still some places where the compiler can’t help us. There are various resources we load from files like images, nibs & xibs and other resources which we need to specify by name, like a view controller we want to load from a storyboard.
(more…)