Methods are public by default: the compiler will always let you invoke them, even if there is no
Methods can be marked as
private method can only be invoked without a receiver, that is, without something before the dot:
class Person private def say(message) puts message end def say_hello say "hello" # OK, no receiver self.say "hello" # Error, self is a receiver other = Person.new "Other" other.say "hello" # Error, other is a receiver end end
private methods are visible by subclasses:
class Employee < Person def say_bye say "bye" # OK end end
Private types can only be referenced inside the namespace where they are defined, and never be fully qualified.
class Foo private class Bar end Bar # OK Foo::Bar # Error end Foo::Bar # Error
private can be used with
alias and constants:
class Foo private ONE = 1 ONE # => 1 end Foo::ONE # Error
protected method can only be invoked on:
- instances of the same type as the current type
- instances in the same namespace (class, struct, module, etc.) as the current type
### Example of 1 class Person protected def say(message) puts message end def say_hello say "hello" # OK, implicit self is a Person self.say "hello" # OK, self is a Person other = Person.new "Other" other.say "hello" # OK, other is a Person end end class Animal def make_a_person_talk person = Person.new person.say "hello" # Error, person is a Person # but current type is an Animal end end one_more = Person.new "One more" one_more.say "hello" # Error, one_more is a Person # but current type is the Program ### Example of 2 module Namespace class Foo protected def foo puts "Hello" end end class Bar def bar # Works, because Foo and Bar are under Namespace Foo.new.foo end end end Namespace::Bar.new.bar
protected class method can be invoked from an instance method and the other way around:
class Person protected def self.say(message) puts message end def say_hello Person.say "hello" # OK end end
Private top-level methods
private top-level method is only visible in the current file.
# In file one.cr private def greet puts "Hello" end greet #=> "Hello" # In file two.cr require "./one" greet # undefined local variable or method 'greet'
This allows you to define helper methods in a file that will only be known in that file.
Private top-level types
private top-level type is only visible in the current file.
# In file one.cr private class Greeter def self.greet "Hello" end end Greeter.greet #=> "Hello" # In file two.cr require "./one" Greeter.greet # undefined constant 'Greeter'