Category Archives for iOS Architecture & Design

Value Objects: AppCode’s Code Generation to the Rescue

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A Value Object is a handy way to combine multiple values in a single object. It sounds simple — you just make each value a property, right? Well, there’s usually more to it than that. There’s even an entire objc.io article about Value Objects. …So how do you define a new Value Object?

I believe in laziness. Let’s do as little work as possible!

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Request Model: How to Architect Web Service Apps

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Objects are like horses. The less they know about their chaotic surroundings, the easier it is to control them.

We don’t want our objects to be spooked when there’s a lot going on. So let’s build ignorance into our systems.

But how? We typically write mobile apps with these things at the center:

  • Communication with web services
  • User interface
  • Object persistence

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Spike Solutions: 7 Techniques You Can Use

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When you’re hiking and don’t know which way to go, what should you do? Stop. Get your bearings.

The same applies to Test Driven Development; sometimes you need to stop doing TDD, and get some answers.

Stop. Get your bearings. Spike Solution Techniques by Jon Reid

Those answers can come by switching from clean code to a style of quick-and-dirty hacking called a “spike solution.” I explained the basic idea in How to TDD the Unknown with a Spike Solution.

But what does it look like in practice?

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How to TDD the Unknown with a Spike Solution

So you want to try Test Driven Development — great! But that requires expressing the intent of the code-to-be in automated tests. Where should you start if you don’t even know what the code should do? What should you do if you’re not confident about a particular approach?

You drive a spike through it!

To start my “Marvel Browser” iOS TDD sample app, I want to begin by making a network call to the Marvel API. If I knew what I was doing, I would start the 3-step “TDD waltz” of writing a single failing test, then writing the simplest code that passes, then refactoring.

But there are two roadblocks keeping me from writing my first test:

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My Dependency Injection Article in the objc.io Testing Issue

objc.io is a monthly online magazine, with an editorial team. Each issue focuses on a particular subject, and Issue #15 is about Testing. I’m honored to be a contributor with my article “Dependency Injection”.

objc.io #15

Books

My article refers to two books I highly recommend:

  • Dependency Injection in .NET by Mark Seemann. This book is marvelous, and I need to study it more. (If you’re wondering why an Objective-C programmer is recommending a book with “.NET” in the title, you need to get out more. Learn what’s going on in other languages, and the smart folks who work in them.)
  • Working Effectively with Legacy Code by Michael Feathers. This now-classic text was instrumental to me when I first got started writing unit tests, helping me break through many conceptual barriers. Feathers boldly defines legacy code as “code without tests.”

Question: Do you have any comments about my Dependency Injection article, or any of the other Testing issue articles? Leave a comment below.

Kent Beck Inspired Video: Oh, the Methods You’ll Compose!

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In the spirit of Dr. Seuss, this video begins,

Dr. Seuss's book, "Oh, The Places You'll Go!"

When a coder sits down to start banging out code,
the first thing to start crowding his cognitive load
is whether his program will do what it should.
“Correctness,” he says, “is what makes my code good.”

But it goes on to explain why clean, readable code matters, and ways to get there…

For such a short video, it has a lot of meat. And I love that last sentence! I really should get a copy of the Kent Beck book that inspired it, Implementation Patterns. (Disclosure: This book link is an affiliate link. If you buy anything, I earn a commission, at no extra cost to you.)

Question: What did you think of the video? Leave a comment below.

Refactoring: The Book that Changed Everything for Me

What would you give to be able to improve your existing codebase with complete safety?

Refactoring book

Disclosure: The book links below are affiliate links. If you buy anything, I earn a commission, at no extra cost to you.

The Refactoring book completely changed the way I code.

In 2001 while searching for information on design patterns, I discovered the original wiki, and stumbled on Extreme Programming. This led me to a software development conference in 2002 called SD West. There I attended a session by Martin Fowler, and knew that I had to pick up his Refactoring book that day.

How could I resist a book that promised to teach me about “improving the design of existing code”?
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