`get() = field.coerceAtLeast(0)` I don't know how ...

# announcements

[Brian Carbone]

get() = field.coerceAtLeast(0)
I don't know how to make a delegate to replace this

[Luke]

Something like this?

class PositiveIntDelegate {
    private var value = 0

    operator fun getValue(thisRef: Any?, property: KProperty<*>) = value

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: Int) {
        this.value = value.coerceAtLeast(0)
    }
}

[Casey Brooks]

A delegate is just a class that has `getValue`/`setValue` operators, such as a Map or a class implementing ReadWriteProperty. So you can just create a delegate class with your custom coercion logic, and use that as the by https://pl.kotl.in/JbGqyFAB7

[Casey Brooks]

Here’s the docs on creating custom delegates, which may help clear it up https://kotlinlang.org/docs/reference/delegated-properties.html#property-delegate-requirements

[Brian Carbone]

oh thanks guys. do libraries which create objects via reflection (e.g. ktor with Content Negotiation) bypass the delegate setter?

[Casey Brooks]

properties with delegates do not have “backing fields”, so you can’t actually use reflection to set the field value itself. If the library sets fields through their setters (not accessing the Field directly), then it should work fine, and it should go through your delegate

[Brian Carbone]

oh I see... it's strange because the value always returns zero when I use the delegate, but every object is made with ktor

[Brian Carbone]

using their content negotiation

[Casey Brooks]

You might try asking over in #ktor

[Brian Carbone]

true, thank you