What's the difference when adding a private modifier to arguments in a Kotlin's constructor?

Question

I'm not sure about the difference between the following two constructors written in Kotlin

class ConcreteItem(val title: String) : Item() {

}

and

class ConcreteItem(private val title: String) : Item() {
}

As you can see, the only difference is the "private" modifier before the title field. How will it affect the scope of the title field?

Answer 1

The following code:

class ConcreteItem(val title: String) : Item() {
}

is a shortcut for:

class ConcreteItem(title: String) : Item() {
    val title: String = title
}

where lack of explicit access modifier for val title implies public:

class ConcreteItem(title: String) : Item() {
    public val title: String = title
}

Similarly, the following code:

class ConcreteItem(private val title: String) : Item() {
}

is a shortcut for:

class ConcreteItem(title: String) : Item() {
    private val title: String = title
}

Taking that in account, the difference between two declarations is simply declaring public property vs private property.

Answer 2

if the private modifier is applied, then a public "getter" won't be synthesized whereby other classes can interrogate the value of "title". otherwise will be.