global methods under object supposedly unaccessible

rubyonrails-talk
1

documentation:

"By default, all methods in Ruby classes are public - accessible by anyone. There are, nonetheless, only two exceptions for this rule: the global methods defined under the Object class, and the initialize method for any class. Both of them are implicitly private."

class Object def something puts "something" end end

=> nil

class XYZ end

=> nil

xyz = XYZ.new

=> #<XYZ:0x10d067580>

xyz.something

something

So then why was I able to access something?

2

1) Post the definition of private.

2) Execute this program:

puts 'hello'

3) What conclusions do you draw from that?

3

A private method is internal to the implementation of a class, and it can only be called by other instance methods of the class (or its subclasses). Private methods are implicitly invoked on self, and may not be explicitly invoked on an object. If m is a private method, then you must ibnvoke it in functional style as m.

But look at this:

1.9.3p0 :032 > class Object 1.9.3p0 :033?> def apple2 1.9.3p0 :034?> puts 'apple2' 1.9.3p0 :035?> end 1.9.3p0 :036?> end => nil 1.9.3p0 :037 > self.apple2 apple2 => nil

Or this:

1.9.3p0 :038 > def apple2 1.9.3p0 :039?> puts 'apple2' 1.9.3p0 :040?> end => nil 1.9.3p0 :041 > self.apple2 apple2 => nil

I invoked apple2 on self (an explicit receiver). However, according to documentation, defining apple2 in Object should have made it private.

Only this would work:

1.9.3p0 :025 > class Object 1.9.3p0 :026?> private 1.9.3p0 :027?> def apple1 1.9.3p0 :028?> puts 'apple1' 1.9.3p0 :029?> end 1.9.3p0 :030?> end => nil 1.9.3p0 :031 > self.apple1 NoMethodError: private method `apple1' called for main:Object

However, in the above example, I was forced to use the private method. The documentation says "any global methods declared outside of a class definition - those methods are defined as private instance methods of Object." In my first examples, I defined a method outside of class definition. But was still able to invoke it on self (self being Object in that case).

4

However, in the above example, I was forced to use the private method.

The documentation says "any global methods declared outside of a class

definition - those methods are defined as private instance methods of

Object."

In my first examples, I defined a method outside of class definition.

But was still able to invoke it on self (self being Object in that

case).

This is one of those cases where irb behaves slightly differently to a ‘normal’ ruby script. If you copy that code into a standalone file and run that then the call to self.apple2 will raise an exception

Fred