Solution: Problems with Kotlin

Well, the solution to [1] is obviously that you are missing a "&&".

This causes Kotlin to assume the expression:

it.address.country == "United Kingdom"

... is the expression that needs to be returned. This causes the code to spit out all people currently in the United Kingdom.

It took me a little while to notice the problem. My IDE didn't help in the slightest.

References

[1] Problems with Kotlin

Problems with Kotlin

So, I was working and it didn't work.

And I really could not understand why.

Here's the code:

    @Test
    fun test() {
        val addressInNetherlands =
            Address(housenumber = 11L, street = "Kerkstraat", city = "Amsterdam", state = null, country = "Netherlands")
        val addressInEngland = Address(12, "Morsestreet", "London", null, "United Kingdom")
        val anotherAddressInEngland = Address(28, "Trinity Ln", "Cambridge", null, "United Kingdom")
        val addressInAmerica = Address(23, "32nd Street", "Columbus", "Ohio", "United States of America")

        val mrBear = Person("Mr.", "Bear", 50, addressInNetherlands)
        val mrBell = Person("Bell", "Graham", 55, addressInAmerica);
        val mrBoole = Person("George", " Boole", 82, addressInEngland);
        val lordKelvin = Person("William","Kelvin",84, anotherAddressInEngland);

        val addressBook = listOf(mrBear, mrBell, mrBoole, lordKelvin)

        var findMrBooleInEngland = addressBook.filter {
            it.firstName == "George" &&
                    it.lastName == "Boole"
                    it.address.country == "United Kingdom"
        }

        assertThat(findMrBooleInEngland).hasSize(1)
    }

Why does the assert fail? (it's programmer error, but almost invisible)

Solution in the next blog post.