wren/doc/site/modules/core/fn.markdown

^title Fn Class

A first class function—an object that wraps an executable chunk of code. Here is a friendly introduction.

Static Methods

Fn.new(function)

Creates a new function from... function. Of course, function is already a function, so this really just returns the argument. It exists mainly to let you create a "bare" function when you don't want to immediately pass it as a block argument to some other method.

:::wren
var fn = Fn.new {
  System.print("The body")
}

It is a runtime error if function is not a function.

Methods

arity

The number of arguments the function requires.

:::wren
System.print(Fn.new {}.arity)             //> 0
System.print(Fn.new {|a, b, c| a }.arity) //> 3

call(args...)

Invokes the function with the given arguments.

:::wren
var fn = Fn.new { |arg|
  System.print(arg)     //> Hello world
}

fn.call("Hello world")

It is a runtime error if the number of arguments given is less than the arity of the function. If more arguments are given than the function's arity they are ignored.