I ruby 1.8.7, Why I can use require in main, but can't use self.require?
require('date') # ok
self.require('date')
NoMethodError: private method `require' called for main:Object
from (irb):22
from /usr/lib/ruby/1.8/date.rb:437
Well known that main is Object class: irb(main):045:0> self => main
irb(main):043:0> self.class
=> Object
But I discovered that it have Kernel mixin:
irb(main):042:0> self.class.included_modules
=> [Kernel]
Moreover, I found that require is private method of self:
irb(main):037:0> self.private_methods
=> [... "require", ...]
Same way, I can't use self.attr_accessor:
irb(main):051:0> class X
irb(main):052:1> self.attr_accessor(:ssss)
irb(main):053:1> end
NoMethodError: private method `attr_accessor' called for X:Class
from (irb):52
from /usr/lib/ruby/1.8/date.rb:437
How does it happend? Can anybody clarify that questions?
Check the following simple example:
class Person
def initialize(age)
@age = age
end
def compare_to(other)
# we're calling a protected method on the other instance of the current class
age <=> other.age
end
# it will not work if we use 'private' here
protected
def age
@age
end
end
In ruby we have implicit and explicit methods receiver, check the next code snippet:
class Foo
def a; end
# call 'a' with explicit 'self' as receiver
def b; self.a; end
# call 'a' with implicit 'self' as receiver
def c; a; end
end
Basically in ruby if a method is private it can be called only on implicit receiver (without self keyword). In your example require is a private method defined the Kernel module and it can be called only on the implicit subject.