Single Responsibility Principle: Is It a Fundamental Mistake?
The “Single Responsibility Principle” (SRP) sounds so noble. But I’m afraid it’s misunderstood and misapplied. Ask your teammates: “What is the Single Responsibility Principle?” Go ahead, ask them. Then ask if the SRP is a good thing or a bad thing. I’d bet many of them will say something like this: “In principle, it’s a good idea. But in practice, it’s overkill.”
SOLID Motivational Posters by Derick Bailey, used under CC BY-SA 3.0 US
On Twitter, Chris Eidhof pointed to an example of taking the Single Responsibility Principle too far. Specifically, Chris was unhappy with the argument that Singletons violate the SRP because, besides their main responsibility, they also manage their own life cycle:
This argument against singletons made me cringe (specifically, the SRP point): https://t.co/C9wVVnqHFs
— Chris Eidhof (@chriseidhof) June 29, 2017
This led to a lively discussion. Many reacted against “over-architecture.” No doubt they experienced fragmented code that grew from over-zealous attempts at SRP.
I think that SRP isn’t just over-applied. It’s fundamentally misunderstood, even misquoted. The repeated misquotes perpetuate that misunderstanding.
Let’s see if we can clear things up, and point to a better way.
Fix Swift tearDown Methods with This AppCode Plugin
Those of you who are regular visitors to qualitycoding.org may have already read Jon’s article outlining the life cycle of XCTestCase objects during the execution of a test suite. If you haven’t, or you want to refresh your memory, take a moment to read the original article.
Jon discusses the importance of the setUp and tearDown methods. And, more specifically, why we should be deallocating our properties in the tearDown method.
Writing a tear down method is one of those repetitive tasks. It follows a specific pattern: all properties should be set to nil. It doesn’t really require any brain power. It’s just one of those annoying tasks that you have to remember to do when writing a test.
It’s tasks like this that should be automated. And now with the Swift tear down inspection AppCode plugin, we can.
Generate Test Scaffolding & Stay Focused
Quickly generate code for either Swift or Objective-C. Code snippets provided for both Xcode and AppCode.
Please Take My 2017 Reader Survey
I want to ensure my platform does the best possible job of answering your needs and interests. And that means I need to know more about you. To do that, I’ve created my 2017 Reader Survey.
Would you please take a few minutes to fill out the survey? By doing so, you will ultimately be helping yourself. Why? Because you will be helping me create content even more interesting and relevant to you.
Your input is important to me. The survey is easy to fill out, and the results are completely anonymous. I can’t tell who said what. And you can finish in five minutes.
Yes, I’m Happy to Help. Take Me to the Survey!Thanks in advance for your help.
Refactoring: Is There More To It than Just Changing Stuff?
Refactoring. It’s a word I hear quite a bit. Usually, in the context of conversations with management, it means, “Rewriting that thing. Hopefully without introducing bugs.” Often, among developers, it means, “One of the options in the Refactoring menu in my IDE.”
Revealing Hidden Objects: Can DDD Improve Your Code?
Code that’s easier to understand, maintain, and extend — that’s the promise of Object-Oriented Programming. But the reality for many iOS developers is that our objects are bloated. They know too much, and do too much. What if our code has hidden objects, waiting to be found?
Each hidden object could provide a new abstraction, a new tool. They could make the code more manageable. Is there a way to discover these hidden objects? Domain Driven Design (DDD) provides a way.
Hide and seek by Nicola Albertini, used under CC BY-NC-ND 2.0
How to Make Swift Mock Objects More Useful
I’ve written about my experience of going to try! Swift Tokyo 2017. Now thanks to the video and transcript provided by Realm, I can also share the talk I gave: “Making Mock Objects More Useful”.
I start by showing the basics of how to make a mock object by hand. But this easily leads to fragile tests because the assertions are overspecified. We need ways to make tests more malleable, with mocks that are more flexible.
How to Safely Parse JSON into Immutable Models, All with TDD
How can we unit test JSON parsing, handling every possible error? Can we generate immutable models? And for Swift, how can we keep our Response Models free of optionals?
Of course, there areb many JSON parsing libraries out there. Plug one in, define all fields as non-optional, and you’re good to go! …Until your app crashes, because something was different in the actual JSON data.
Conflict 3 by Flavio~, used under CC BY-NC 2.0
Unlikely? “The backend team would never do that to us”? I’ve had a released app crash because the backend folks changed one field from a string to an integer. I’ve seen app development and QA forced to pause because a commit assumed all fields were non-optional. (It crashed on the missing field, because Swift.)
So let’s look at a pattern that will help us
- Handle required types
- Avoid optionals
- Deliver immutable models
Even if you never plan to do your own parsing, we’ll learn things along the way about design and testing.
Love Swift? Want to Visit Charming / Quirky Japan?
If you’re interested in Swift development, and want to visit Japan, start making plans to go to the next try! Swift conference in Tokyo. It was my privilege to be a speaker earlier this month.
Let me share my impressions of the conference, and why you might consider making the trip there.
(But first, a side-note about this blog: Sorry I’ve been so quiet lately! I was spending my time preparing for try! Swift Tokyo 2017. Next up is CocoaConf Chicago, where I’ll be leading a TDD workshop in addition to giving a talk. But I’ve also continued to TDD a JSON parsing example, in both Objective-C and Swift versions, so I have plenty to blog about. To make sure you don’t miss any new articles, you can sign up to get updates via email.)
Logo
“Riko”, the official logo of try! Swift Tokyo
First, let me point out the conference’s logo/mascot. The Swift bird has never been so adorable! Without a doubt, this is the cutest tech conference logo I’ve ever seen.
Let’s Stop Overusing Swift Equatables in Unit Tests
Enumerations with associated values are my favorite feature of Swift. But how can we write unit tests against them? “Make them Equatable and use XCTAssertEqual” is common advice.
I’m here to argue otherwise. In fact, let’s use this as a jumping-off point to discuss Swift Equatables in unit tests.
In Defense of Uncle Bob’s Dark Path: Swift and Testability
Uncle Bob set off another firestorm with his blog post The Dark Path. Condemnation from the Swift programming community was, well, swift. How dare he insult our wonderful new language? Clearly he’s a n00b who hasn’t done enough Swift programming.
Except that he’s no n00b — not even close. As Mark Seemann said,
Perhaps you disagree with @unclebobmartin (at times I do), but remember: he's been programming all of YOUR LIFE. Don't presume him ignorant.
— Mark Seemann (@ploeh) January 14, 2017
I’m here to defend Uncle Bob’s post, as it relates to unit testing and TDD.