Bob I’m an iOS instructor/blogger from S.Korea.July 14 • 5 min read • Edit

Top 10 Ground Rules for iOS Developers

What I’ve learned so far


You’ve been around with Swift for a couple of weeks. But, you feel like you aren’t sure whether you produce decent stuff. You ask these questions, “Are they good looking? Readable? How do others go about?” Certainly, there are a couple unspoken/spoken rules. So, I wrote this tutorial for you.☝️ I’ve attached my YouTube lessons and articles here and there, so check them out if you need to.

Disclaimer: This list purely comes from my brain. It’s about what it feels like to be an okay Swift developer. I’m biased. This is what I’ve found after having read the Swift documentation and WWDC videos while preparing my courses and making apps.

1. Indentation, not Swifty enough.

I’ve seen too many developers writing code like this below,

func neverDoThis()
  let fuglyCode = true
  if (fuglyCode == true)
    print("This is atrocious")

If I see the type of code above, I judge real hard.🤔 I assume that he/she has never read the API guideline/documentation or anyone’s Swift code before. Let’s take a look at how Apple engineers at WWDC would write.

// How Swift engineers would write
func swiftyWay() {
  let isLegit = true
  if isLegit {
    print("This is fine")

If you spot anyone using the atrocious way, smack him in the head (gently)


2016 WWDC Swift API Design Guidelines (YouTube)

2, Never Use Try!, as!, String! Unless %100 Sure

If you’ve been around, make sure you understand the differences between,

as as! as?

try try! try?

Int Int! Int?

If you don’t know what the heck you are doing and you resort to those 😡s on the left side of Xcode, you are bound to see that, “Found unexpected nil” message. Stop being passive. Move your butt and understand what they mean. Especially for those who took beginner courses on Udemy (including myself), you need to figure out your own.


Learn Swift with Bob (Udemy)

3. Never make function more than 20 lines

My friend asked me to review his code yesterday. One function had 50 lines. It covered the entire Xcode black screen. I was like, this shit isn’t going anywhere. I told him, “I don’t want to read your code because your code is fucking ugly”. I told him to break it into pieces and modularize. The truth hurts but he is my friend and I needed to be real and clear. No bullshit trying to please him.

For example, instead of writing something like this, although the below is not too crazy,

An example of GCD Code

Break it down into pieces.

Nice and neat

Nice and Neat

4. UI Main Thread, Networking Background Thread

The concept of mult-threatding (a group of tasks done by CPU) is daunting. I don’t blame you. I don’t have a computer engineering background, and I still don’t know much of it.

I wrote two articles why you need to use the main thread for UI updates and the background threads for networking. So, I will skip this part.


Intro to Grand Dispatch Central with Bob (Medium) UI and Networking like a Boss in Swift 3 (Part 2) (Medium)

5. Don’t make Swift file over 200 lines

I made this mistake when I first learned how to make apps. I made a file with more than 800 lines which include multiple UIViewController classes and models. It’s something that I wouldn’t repeat. Once you hack, you never go back. Of course, if a file is JSON or content based, it may contain more than thousands of lines.

I’m not going to explain all these concepts in detail but I will tell you what you could study and make your entire app nice and clean.

There are a couple ways to fundamentally reduce the number of lines and still be readable. You can make reusable code using Protocol Oriented Programming with UITableVIew and UICollectionView. If you are using MVC which stands for Massive View Controller you may want to find out how MVVM works.


Intro to Protocol Oriented Programming (Medium) Protocol Oriented MVVM in Swift 2.0 (Natasha)

6. Never hard type anything. Enums, Enums, Enums

Have you realized that the reason we can auto-complete a lot of properties in Xcode is due to Enums? It may seem obviously, but maybe not so for beginners.

The last thing you want to do in programming is hardcore typing rather than picking and choosing. For example, when you make UIAlertViewStyle, UIKit engineers created,

public enum UIAlertViewStyle : Int {
 case `default`
 case secureTextInput
 case plainTextInput
 case loginAndPasswordInput

Can you ever imagine typing each case? I can’t because I don’t think about it since it’s a must. Do not hard code not only for yourself, but for the sake of grey hair of your teammates.


Chapter 7: Advanced Enums (Udemy)

7. Name. Be descriptive. Styling Guide

According to the Swift API guideline, there were a couple standards developers should go by.

1. Convention > Uniqueness

Every programming language has its own character and style. Although subjective, the convention can be found through reading the Swift documentation and Swift files written in open-sourced projects. Again, I highly recommend you to take a look what it feel to write with a Swifty manner. Instead giving you examples, I will provide you with resources down below.

2. Expressive > Impressive

There are some dudes who like to make things twisted so that they feel a sense of superiority since others can’t read. This is bullshit. No one should ever do this. It’s all about effective communication with one another. Yes, code is a way humans talk to computers. But, it’s also between us, developers and geeks. Please don’t be that arrogant dude who tries to use Shakespearish words to impress. No need.

3. Clarity > Brevity

Swift developers ask us to be clear with names so that when we come back three weeks later, we are good. However, there is no black and white. It’s the balance between using descriptive names and reducing the number of lines overall at the same.

“Brevity itself is not a worthwhile goal. Concise code is a consequence of using contextual cues” — Doug Gregor, Swift Engineer

// Too brief & Lack of context
let a = "A"
let b = "B"

If I were to read the code above, I would be confused what exactly a and b stand for throughout. So, I have to go all the way to find what they are. Why can’t we be a little more descriptive by writing,

// How I would do it
let capLetterA = "A"
let capLetterB = "B"

8. Use Guard

The Guard statement is not only useful for unwrapping optioanls but also for replacing if-else statements and provide an early exit out of the function using break or using return. It allows anyone to identify what would happen if the condition isn’t met without scrolling all the way to find that else block. Let’s take a look at a real-world example.

let name = "Bobby"
func checkName() {
  // Early Check
  guard name == "Bob" else {
  print("You ain't Bob")

 // I can do anything I want without seeing the else block.
 // So much freedom
 // You don't even need to read this
 // Why are you even reading this
 // Now, you may leave. I'm not going to say anything important
 // In this block of code

 // Lol... you still here?

 print("You Good, bro")

If you don’t understand what it means to unwrap optionals and have an early exit, check the resources down below.

9. Don’t use NS if you can

I do not code in Objective C, so I try to avoid it as much as I can both mentally and physically. Unless you are interacting with Objective-C APIs, stay away from using NS even if Swift automatically converts some Objective-C types to Swift types, and some Swift types to Objective-C types.

It is true that Swift is inspired by Objective-C and many other languages, however, it is an independent language. I’m not sure how much the conversion slows down, but it’s recommended Swift developers avoid if possible. You can take a look at the alternatives since Swift provide its own native libraries and APIs.

If you are using Swift 3 and above, don’t use NS unless you have to

“Historical Note: If you’re wondering why so many of the classes you encounter have an NS prefix, it’s because of the past history of Cocoa and Cocoa Touch. Cocoa began life as the collected frameworks used to build apps for the NeXTStep operating system. When Apple purchased NeXT back in 1996, much of NeXTStep was incorporated into OS X, including the existing class names. Cocoa Touch was introduced as the iOS equivalent of Cocoa; some classes are available in both Cocoa and Cocoa Touch, though there are also a large number of classes unique to each platform. Two-letter prefixes like NS and UI (for User Interface elements on iOS) are reserved for use by Apple”. — Apple

10. Don’t Rely on Segues

Beginners tend to make too many Segues to a point when storyboards look like a spider web. Once you go beyond a certain threshold, it becomes unmanageable and hard to track each viewcontroller. Therefore, use Delegate/NSNotification to send data. Use multiple storyboards instead of one. If you are comfortable with Delegate, you can start using RxSwift or ReactiveCocoa to pass data or send notifications with just a couple lines of code. This topic is a bit too broad, so I will break it down into piece in later with YouTube videos and Medium articles.

About Me

iOS Developer from South Korea. Feel free to follow my story on Instagram or get serious on LinkedIn