# Interface Callback<P,R>

Type Parameters:
  `P` - The type of the argument provided to the `call` method.
  `R` - The type of the return type of the `call` method.

All Known Implementing Classes:
  `MapValueFactory`, `PropertyValueFactory`, `TreeItemPropertyValueFactory`

Functional Interface:
  This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface public interface Callback<P,R>
The Callback interface is designed to allow for a common, reusable interface to exist for defining APIs that requires a call back in certain situations.

Callback is defined with two generic parameters: the first parameter specifies the type of the object passed in to the `call` method, with the second parameter specifying the return type of the method.

Since:
  JavaFX 2.0

- ## Method Summary

  Modifier and Type
  Method
  Description
  `R`
  `call(P param)`
  The `call` method is called when required, and is given a single argument of type P, with a requirement that an object of type R is returned.

- ## Method Details

  - ### call

    R call(P param)
    The `call` method is called when required, and is given a single argument of type P, with a requirement that an object of type R is returned.
    Parameters:
      `param` - The single argument upon which the returned value should be determined.
    Returns:
      An object of type R that may be determined based on the provided parameter value.