What methods can prevent or eliminate the problem of unwanted side effects in code?

Several approaches are used to prevent or eliminate unwanted side effects in code:

• Immutability of data: Using immutable objects and data structures helps avoid state changes that can lead to side effects.
• Pure functions: Functions that do not modify external state and always return the same result for the same inputs.
• State isolation: Separating state and logic so that changes are localized and controllable.
• Use of architectural patterns (e.g., MVVM, MVI) that facilitate state management and minimize side effects.
• Testing and refactoring: Regularly covering code with tests and improving code structure to identify and eliminate side effects.

Example in Kotlin using a pure function:

fun add(a: Int, b: Int): Int {
    return a + b // does not change external state
}

Unlike a function that modifies a global variable, which can lead to side effects.