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How to eliminate if-else chain, for long life software

Sameh Muhammed on October 10, 2022

Motivation All programing principles and paradigms aim to enhance code readability and maintainability, from OOP to functional, SOLID, D...

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Jean-Michel 🕵🏻‍♂️ Fayard • Oct 11 '22

Agree with all your points.

Language specific, but in Kotlin the when expression is a massive improvment over if/else

val message = when (x) {
    in 1..10 -> "x is in the range"
    in validNumbers -> "x is valid"
    !in 10..20 -> "x is outside the range"
    else -> "none of the above"
}
println("validate($x): $message")

Sameh Muhammed • Oct 11 '22

Yes, good tip but i don't use Kotlin that much, it's language specific but the idea is to make code more readable.

Jean-Michel 🕵🏻‍♂️ Fayard • Oct 11 '22

I wonder what other languages have a similarly good structure.
Not like switch case which don't return anything, something better.
Probably functional languages in general?

Mario Santini • Oct 11 '22

Like switch expressions for Java v12 have a look

Jean-Michel 🕵🏻‍♂️ Fayard • Oct 11 '22

indeed yes, I didn't know they can return a value

Patrick Elsen • Oct 11 '22

Rust has a nice match statement too, even though it is not functional.

match person {
    Person::Employee(employee) if employee.years() > 3 => true,
    Person::Employee(employee) if employee.age() >63 => true,
    Person::Intern(internet) if intern.name().first() == 'S' => true,
    _ => false
}

I believe it is something that most functional language have and newer languages are starting to adopt it.

Swastik Baranwal • Oct 12 '22

Almost every modern language have pattern matching.

Jean-Michel 🕵🏻‍♂️ Fayard • Oct 12 '22

Tree patterns are used in some programming languages as a general tool to process data based on its structure, e.g. C#,[1] F#,[2] Haskell,[3] ML, Python,[4] Ruby,[5] Rust,[6] Scala,[7] Swift[8] and the symbolic mathematics language Mathematica have special syntax for expressing tree patterns and a language construct for conditional execution and value retrieval based on it.

In computer science, pattern matching is the act of checking a given sequence of tokens for the presence of the constituents of some pattern. In contrast to pattern recognition, the match usually has to be exact: "either it will or will not be a match." The patterns generally have the form of either sequences or tree structures. Uses of pattern matching include outputting the locations of a pattern within a token sequence, to output some component of the matched pattern, and to substitute the matching pattern with some other token sequence.

Nick • Oct 13 '22

The techniques above are called pattern matching. I wrote an article about it here:
dev.to/n1ckdm/pattern-matching-dec...

Jean-Michel 🕵🏻‍♂️ Fayard • Oct 13 '22

Really good article thanks
Not that Kotlin when is not true pattern matching found in more fiftieth languages, it's a better switch case. Combined with static types and algebraic types it's 80% of that though

Matthew Daly • Oct 15 '22

Newer versions of PHP have match.

Ben Sinclair • Oct 19 '22

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Sameh Muhammed • Oct 19 '22

Thanks! , great idea

Robert • Oct 12 '22

I would say be aware of polymorphism. It's not wrong, but not the only concept.
The principle composition over inheritance is often a better choice, because you don't couple classes with an inheritance structure.
Sometimes it's a great mix to use inheritance for the structure and composition for the logic.

peerreynders • Oct 12 '22

Sometimes it's a great mix to use inheritance for the structure and composition for the logic.

i.e. prefer interface inheritance (implements; for polymorphism) over implementation inheritance (extends).

The original quote (GoF, 1994, p.20):

Favour object composition over class inheritance

talks about implementation inheritance.

Sameh Muhammed • Oct 12 '22

Actually, we talked about this principle here Composition vs Inheritance, take a look 😉

Juan Vega • Oct 14 '22

Good post.

Just to add something, there is another possible iteration when you have a set of fixed conditions (like the switch), for large number of options a map is a better and more readable approach.

Kacper Turowski • Oct 11 '22

I am SOOOO HAPPY to see your article. For once it's "how to do it better" and not "omigosh, you should NEVER nest if-s, here's why". Glad to see people who don't clickbait.