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Discarding setters

Aleksi Kauppila on September 08, 2018

Setters, or mutators are used very commonly when working with classes. Almost every person who's ever written a class has also written some setter ...
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Adrian B.G. •

Nothing is white or black, do not take it to extreme.

Use setters only when needed, not by default, prefer immutability, and that is it.

They are not the Evil or Satan, just a tool, use it when needed.

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Oliver Mensah •

That's an awesome piece. However, I find that setters have a place in value objects where mutability is really essential. But in services setters are should not be allowed as they are supposed to be immutability created.

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Aleksi Kauppila •

Thanks Oliver!

I'm curious, why do you think it's essential that value objects are mutable?

final class EmailAddress
{
    private $address;

    public function __construct(string $emailAddress)
    {
        $this->address = $emailAddress;
    }
    // ...
}

What benefits would we gain if this example was mutable? Or, would it make DateTime worse, if calling $dateTime->modify("+1 day") would return a new instance of DateTime instead of altering it's inner state?

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Oliver Mensah •

Not in cases that setters and gettings will be valuable. In this case, using setters won't be of much importance. In the case that you want setters to be used, the emphasis on constructor injection is less as compared to settor injection.