Command Shift

iOS development and other nonsense

Nice Web Services, Swift Edition

As I’ve written before I am very keen on getting web service results out of JSON and into a strongly typed form as soon as possible. It makes the rest of your code much cleaner, insulates you from knowledge of the web service keys and format and aids testing.

Swift structs are a natural home for your web service results - they are immutable, lightweight and have minimal boilerplate code requirements. Getting the results out of JSON and into a struct, however, can be complicated - verifying the correctness of each key in the JSON can quickly lead to an if let staircase of doom.

I wanted to use something clever and functional, but this has readability drawbacks (I’m not yet comfortable with scattering custom operators all over the place) and also requires me to write a curried initializer for each struct, which seemed like repeating myself a bit too much.

My design goals were:

  • Minimise repetition of code and boilerplate
  • Allow for flexibility if the API changes
  • Allow for optional properties
  • Take advantage of compile-time checking
  • Feel at least slightly like I had done something a bit “Swifty”

Here’s what I came up with.

Storyboards in Xcode 6

I’ve liked the idea of storyboards since their introduction, and even used them a couple of times, but I’ve always gone back to laying out views in code, mostly using my autolayout category.

It’s clear that Apple would prefer us to be using interface builder and storyboards, so every time a new version of Xcode comes out I give it a try to see if I’m ready to move on. Here are the results for Xcode 6, after I’ve spent the last few weeks building a universal app for iOS 7 and 8 using storyboards.

Functional Functions

Functional programming for people who know nothing about functional programming by someone who knows next to nothing about functional programming : a series

The introduction of Swift has brought with it a lot of talk about functional programming. I’d previously only heard the term whilst investigating things like Reactive Cocoa, and had not investigated too deeply because the documentation for that was so full of arcane new terms1, but now it sounds dangerously like becoming mainstream.

As I’ve previously mentioned, I learnt to code on the streets, not some fancy computer school. It looks like I’m going to have to go back out there and work out what this new2 menace is.

Parenting and Programming

My second daughter was born this week. In a change to your usual programming, here’s a little whimsical reflection on the parallels between being a parent (though my experience of the former only goes up to 4 years) and being a programmer. Mostly because it’s hard to write code-based blogs with a sleeping baby on your lap.

Understanding Optionals in Swift

What are they for?

In Objective-C, you can safely send a message to nil, which will return something treated as nil, or NO, or 0 (this variety is part of the reason Swift has optionals, of which more later). This is a useful and powerful feature, but it only applies to Objective-C objects. There’s no universal way to deal with absent or no-value types such as integers, floats or Booleans. Things like NSNotFound, NSIntegerMax,-1 or 0 are used to represent “no value” in these cases.

Optionals are Swift’s way of unifying the representation of Nothingness. By using them, we lose some of the ease and flexibility of nil messaging, but gain compile-time checking, safety and a consistent way of dealing with the same problem, regardless of variable type.

It's Not Your Fault

It’s quite telling that one of my highest voted Stack Overflow answers relates to nothing more than a simple misunderstanding of language. Apple’s use of the term fault in Core Data seems to cause quite a lot of confusion.

Apple to tend to use a ten-dollar word when a cheaper one will do in their APIs (ubiquity or segue, anyone?), but it’s usually a correct and unambiguous one. Fault, particularly when seen in a log statement, is all too readily interpreted as error.

Stop Nesting Animation Blocks

Chaining animations together has always been a little bit awkward. You’d do the first step, then in the completion block, do the second step, then in that completion block, do the third step, and so on, until you close it all off with a staircase of doom:


You don’t need to do this.

Using Dispatch Groups to Wait for Multiple Web Services

Imagine your app has to run a series of nice web service calls. These could be for a set-up task, for example - when your app launches it may need to get various bits of configuration information from a server. This could involve hitting several endpoints.

You want to call a single method to kick this process off, and have a completion block run when it has finished. The web services don’t depend on each other. How can this be done?

Autolayout in Interface Builder - Xcode 5.1

Other posts in the autolayout series:

They killed clippy.

Interface builder in Xcode 4 was so bad at managing autolayout, and yet autolayout was so good, that it drove me to abandon it entirely and build my interfaces in code. With Xcode 5.1, it appears that most of these wrongs have been corrected.

My previous post on autolayout in interface builder (IB) was basically a list of workarounds and tips on what not to do to upset the fragile system of constraints that you’d created. This post will be about how to work with the editor to get the layout you want.