Inject constructor and companion object

Question

I'm kind of new to Kotlin and I'm trying to Inject a value (in this example it is just an Int but in the real code it is a Provider class) What am I doing wrong here? and why is x is an unresolved reference?

class Test
@Inject constructor(private val x: Int) {

companion object {
    var y: Int = 0

        @BeforeClass @JvmStatic
        fun beforeClass() {
            y = x * 2
        }
    }
}

score 4 · Accepted Answer · answered May 12 '17 at 20:13

A companion object is a static object associated with a class, not with an instance of a class.

class Foo(val bar: Baz) {
    companion object {}
}

is similar to the following code in Java:

class Foo {
    static class Companion { }
    static final Foo.Companion Companion = new Foo.Companion();

    final Baz bar;
    Foo(Baz bar) { this.bar = bar; }
}

This is why x is not in the variable scope of the companion object, just like you cannot access the bar field from the static class Companion. Your property y is actually a field in the Test.Companion class.

I'm not sure what you're trying to do with the BeforeClass thing, since I'm not familiar with it. Hope my answer helps anyway.

Inject constructor and companion object

1 Answers1