Quick Answer

Handling nullable types safely

Understanding the Issue

Kotlin's type system distinguishes nullable from non-nullable types. Safe calls (?.), Elvis operator (?:), and non-null assertions (!!) help handle null cases explicitly.

The Problem

This code demonstrates the issue:

Kotlin Error 
// Problem: Unsafe null usage
val length: Int = nullableString.length // Error

The Solution

Here's the corrected code:

Kotlin Fixed 
// Solution 1: Safe call
val length: Int? = nullableString?.length

// Solution 2: Elvis operator
val length: Int = nullableString?.length ?: 0

// Solution 3: Non-null assertion (only when sure)
val length: Int = nullableString!!.length

Key Takeaways

Always handle null cases explicitly using Kotlin's null safety operators.