Kotlin is a modern, concise, and safe programming language that is fully interoperable with Java. It is designed to be more expressive and concise than Java, with features that help avoid common programming errors.
Kotlin Anti-Patterns Overview
Kotlin, despite being a modern and well-designed language, still has common anti-patterns that can lead to bugs, performance issues, and maintenance problems. Here are the most important anti-patterns to avoid when writing Kotlin code.
Using !! Operator Excessively
The !!
operator forces a nullable type to be non-null and throws a NullPointerException
if the value is null. Use safe calls (?.
) and the Elvis operator (?:
) instead.
Not Using Data Classes for Simple Data Holders
Use data classes for simple data containers to automatically get equals()
, hashCode()
, toString()
, and copy()
methods.
Ignoring Nullability in Platform Types
Platform types (types coming from Java) may be nullable even if not marked as such. Always handle them carefully.
Overusing Extension Functions
While extension functions are powerful, overusing them can lead to namespace pollution. Group related functions in utility classes or objects.
Not Using Coroutines for Asynchronous Operations
Use coroutines for asynchronous operations instead of callbacks or threads for more readable and maintainable code.
Not Using Kotlin's Standard Library Functions
Kotlin’s standard library provides many useful functions. Use them instead of reimplementing common functionality.
Not Using Property Delegation
Use property delegation (lazy
, Delegates.observable
, etc.) for common property patterns.
Not Using Sealed Classes for State
Use sealed classes to represent states with associated data instead of using constants or enums.
Not Using Scope Functions
Use scope functions (let
, run
, with
, apply
, also
) to make code more concise and readable.
Not Using Inline Functions for Higher-Order Functions
Use inline
for higher-order functions to avoid the overhead of lambda object creation and virtual function calls.
Not Using Companion Objects Properly
Use companion objects for factory methods and static utilities, not for instance-related functionality.
Not Using Type Aliases for Complex Types
Use type aliases to give meaningful names to complex types, making code more readable and maintainable.
Not Using Extension Properties
Use extension properties instead of extension functions when the function doesn’t take parameters and returns a value.
Not Using Object Expressions for Interfaces
For single-method interfaces (SAM interfaces), use lambda expressions instead of object expressions.
Not Using Kotlin's Collection Operations
Use Kotlin’s collection operations (map
, filter
, reduce
, etc.) for more concise and readable code.
Not Using Destructuring Declarations
Use destructuring declarations to extract multiple values from objects like pairs, triples, and data classes.
Not Using Kotlin's String Templates
Use string templates ($variable
or ${expression}
) instead of string concatenation for more readable code.
Not Using Named Arguments
Use named arguments for better readability, especially when calling functions with many parameters.
Not Using Kotlin's Flow for Reactive Programming
Use Kotlin’s Flow for reactive programming instead of callbacks or custom observer patterns.