A major difference between making your own apps and making apps for others as a contractor or "professional" developer (a common step as people move from hobbyist or indie developers to perhaps more lucrative work) will be the web services you're asked to interact with.
Nobody's going to pay you to make a Flickr or Twitter client, which is inconvenient because that's what most of the online examples seem to use. If you've never written code that interacts with a web API before, it's hard to approach these things with confidence, especially if you're expected to talk to the developers of that API to work out any issues, and if those APIs are being written and rewritten in parallel with the development of the app.
In this article I'm going to go over the basics of your networking code. I'm going to assume you're working with an API from this century so we're talking about JSON and REST1. If you're hearing terms like SOAP from your web people then run away.
I'm not going to define REST to mean anything other than "things are at a URL", have that argument somewhere else ↩
You're a great developer. Look at the quality blogs you read. If you're starting a project today you'll be using storyboards, organising your code in groups, everything will be well commented and it'll be obvious in three years time what's going on.
Meanwhile, back in reality, you're working on an app that was first written for iOS4 and each of the dozen developers who've had a month to implement or fix things since then have gone in, done their stuff and moved on. Things get complicated. If you're asked to work on an app, either to bolt more stuff onto it or (hooray!) to do some cleanup, then the very first thing you need to do is work out where you are and what's going on.
I gave a lightning talk at iOSDevUK this year. I had five minutes to talk, so thought I'd cover the relatively simple(!) topic of how to navigate a massive, new codebase when you're dropped in as a new developer and asked to fix problems or implement new features, right now. Here are the points I was trying to get across.
I recently worked on an app featuring a photo browser. The work involved updating the code (previously using Assets Library) to use the Photos framework.
I found out a few things that don't seem to be represented very well in the documentation or the examples floating round online, so here they are.
When iOS 6 came out, we were in the early stages of planning for a major project. We managed to convince the client that the new app should be iOS 6 only, and decided to go all-in on the new features.
The two biggest new features, which we used almost everywhere in the app, were collection views and autolayout.
The app was built almost entirely in code, meaning a lot of constraint creation. My autolayout helper category was written to help build it.
Now it's time for that category, and all the others (and there are loads), to be deprecated.
"Don't Repeat Yourself" is a solid bit of programming wisdom. It's so common it has been made into an acronym, DRY, which means that people get to make "jokes" about DRYing out their codebase.
If you write a bit of code that does something, and elsewhere in your program you need to do the same or a very similar thing, don't copy and paste the bit of code. Make it accessible from both places, and make the minimum set of changes needed to make it reusable.
"Boilerplate" code refers to code that has to be included regularly and without much alteration to achieve basic functionality. There are plenty of frequent, common operations that require a lot of boilerplate code. The boilerplate code obscures what you actually want to do and makes the program harder to read. A good example is inserting managed objects into a context. For each type of managed object, the code looks almost exactly the same, but different types are involved.
I'm going to discuss some of the boilerplate code encountered in Core Data, and how you can use Swift generics to DRY out some of these operations. First, a few words about generics.
iOS devices have small screens. Sometimes we want more content to be included on a screen and adding it to a scroll view is a great way of doing this. I'm going to look at the various numbers and measurements that a scroll view uses to do its job.
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 letstaircase 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.
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 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.
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.