Swift vs Kotlin- Nullability

I recently began learning iOS development using Swift, and I have found that it is very similar to Kotlin.

Along the way, I learned about a concept called Optional, which is known in Kotlin as Nullable.

So let’s learn how Kotlin and Swift handle optional/nullable variables.

• Swift has a concept called Optional, which means values can be absent (nil)
• Kotlin has a concept called Nullable, which means that values can be absent (null)

Declaring optional/nullable

• Swift

var name:String?

• Kotlin

var name:String?

Let’s explore how optional/nullable can be handled in various ways

! Force unwrap !!

// Swift !
var name:String? = "Swift"
print("Name is \(name!)")

// Koltin !!
var name:String? = "Kotlin"
print("Name is: ${name!!}")

nil coalescing operator ?? Elvis operator ?:

// Swift ?? 
var name:String? = nil
print("Name is \(name ?? "Swift")")

// Koltin ?:
var name:String? = "Kotlin"
print("Name is: ${name ?: "Kotlin"}")

Check for nullable/optional using the if statement

// Swift if statement
var name:String? = nil

if name != nil {
    // Swift is not smart enough here to inference the type of name.
    // name is still optional here 🤯
    print("Name is \(name ?? "Swift")")
}

// Koltin if statement
var name:String? = "Kotlin"

if(name != null){
    // Kotlin is smart enough to infer the type of name here as String 😎
    print("Name is: $name")
}

Optional binding(if let) and scope functions(let, also, etc.)

// Swift if let optional binding
var name:String? = nil

if let name = name{
    // Here the type of name is String
    print("Safe value received: \(name)")
}else{
    print("Name is still null")
}

// Koltin's scope function
var name:String? = "Kotlin"

name?.let{nonNullableName->
    // Kotlin is smart enough to infer the type of name here as String 😎
    print("Name is: $nonNullableName")
}

Chaining

  struct Language{
      let name:String
  }
  
  // Optional object
  var swift:Language? = Language(name: "Swift")
  
  // Note here object is nullable not its property
  print("Language name:\(swift?.name ?? "Swift")")

data class Language(val name: String)

var kotlin:Language? = Language("Kotlin")

print("Name is: ${kotlin?.name}")

guard let

func getFormattedName(name: String?) -> String{
    
    guard let name = name else {
        // fallback name
        return "No name found" 
    }
       
    // only executes if name is not nil
    return "Nmae is: \(name)" 
}

// call the func and print its result
print("Formatted name: \(getFormattedName(name: nil))")

Check the full code for Swift

Swift optionals

Check the full code for kotlin

Kotlin Nullability

References

The Basics - The Swift Programming Language (Swift 5.7)

https://kotlinlang.org/docs/null-safety.html

Apple Developer Documentation

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