Member variables cannot be correctly converted to lambda expressions

Question

As above

data class Person(val name: String, val age: Int) : Comparable<Person> {
    override fun compareTo(other: Person): Int {
        return compareValuesBy(this, other, Person::name, Person::age)
    }
}

The above code is running correctly, when I convert to the following code, I can't get the correct result.

data class Person(val name: String, val age: Int) : Comparable<Person> {
    override fun compareTo(other: Person): Int {
        return compareValuesBy(this, other, { name }, { age })
    }
}

what are you trying to achieve here? Why do you think that syntax would work — Tim, Jan 14 '19 at 09:20
@TimCastelijns I think what member variables can do, lambda can do it, so I want to convert it. — zm chen, Jan 14 '19 at 09:29
@Cililing `val person = listOf(Person("Bob", 20), Person("Bob", 12)` `println(person[0] > person[1])` — zm chen, Jan 14 '19 at 09:30

score 1 · Accepted Answer · answered Jan 14 '19 at 11:33

You should use it inside curly brackets and then access name and age. if you don't do that compiler accept your first argument( after this, other) that is name in this case as Person Object not String

This code will work for you:

data class Person(val name: String, val age: Int) : Comparable<Person> {
  override fun compareTo(other: Person): Int {
    return compareValuesBy(this,other,{it.name},{it.age})
   }
}

Member variables cannot be correctly converted to lambda expressions

1 Answers1