An irb session with self so help yorselves rhyms with elves doesn't it?

bad_method.rb

class << self!
end
# => NoMethodError: undefined method `self!' for main:Object

class << self
end
# => nil

self.class
# => Object

Myclass = Class.new
# => Myclass

Myclass.class
# => Class

Myclass << self
end
# => NoMethodError: undefined method `<<' for Myclass:Class

class Myclass << self
end
# => SyntaxError: (irb):13: syntax error, unexpected tLSHFT, expecting '<' or ';' or '\n'

class Myclass < self
end
# => TypeError: superclass mismatch for class Myclass

Myclass = Object.new
# =>  warning: already initialized constant Myclass
# =>  #<Object:0x136f6b0>

Myobject = Object.new
# =>  #<Object:0x1022940>

Myobject.self
# => NoMethodError: undefined method `self' for #<Object:0x1022940>

Myobject.self!
# => NoMethodError: undefined method `self!' for #<Object:0x1022940>
 
Myobject < self
# => NoMethodError: undefined method `<' for #<Object:0x1022940>

Myobject << self
# => NoMethodError: undefined method `<<' for #<Object:0x1022940>

class Myobject < self
end
# => TypeError: Myobject is not a class

Myobject.class
# => Object

Myclass.class
# => Object

python
# => NameError: undefined local variable or method `python' for main:Object

eval "class<<self;p self!;end"
# => undefined method `self!' for #<Class:#<Object:0xb94dee3c>> Epiphany! tada! But didn't you just p yourself?

# This is what we want 
eval "class<<self;p self;end
# => #<Class:#<Object:0xb94dee3c>>

myclass.rb

self
# => main

self!
# => NoMethodError: undefined method `self!' for main:Object

Myclass = Class.new
# => Myclass

Myclass << self!
# => NoMethodError: undefined method `self!' for main:Object

xxxx.rb

self
# => main

class
# => SyntaxError: (irb):2: syntax error, unexpected $end

class ::self!
# => SyntaxError: unexpected tFID, expecting tIDENTIFIER or tCONSTANT


[16] pry(main)> class << self!
[16] pry(main)*   
# baby wants something?

class.class
# => self

# K! nuff messin with banging my self

class << self
  "a gallon of fresh milk".send :self
  "Over?!"
end

class.self
# => SyntaxError: unexpected '.' did baby drop something?

"Goo goo says baby Ruby".send :self
# => "HAHA" Oh no it's too late!

self! is not a valid method because self is a keyword. the bang operator denotes that you are applying a dangerous method ( one that modifies it's receiver ).

>> class << self!
>> class
>> class.class
>> self

In these last three, where you are getting the >> prompt, it hasn't finished defning the class that you started to define. Finish defining it by adding and end and possibly another end (there were two class definitions you started here. That should bring up any errors (and you should have an error here).

I assumed that he read the error messages from the second one and understood that part of the story. To carry your explanation further, and more to the point, the lowercase letter designates that it is either a local variable or a method in the first place. We never get to the point to worry about the bang part of the method name.

About self, it is true what you say... however, it isn't the whole story....

>> def self    
>> puts "HAHA" 
>> end         
=> nil         
>> self        
=> main        
>> self.send(:s
HAHA           
=> nil         

Whoops... that 3rd line from the end is supposed to be:

>> self.send(:self)

I never seem to get the whole story till some time later and it comes like a revelation. HAHA!

There we go... glad you saw it! Hope it helped.

So what did _why the lucky stiff mean by class << self! in the baby talk image?

Maybe?
def self!
"self bang is open then"
end

[22] pry(main)> def self
[22] pry(main)* "self is self?"
[22] pry(main)* end
=> :self
[23] pry(main)> self
=> main
[24] pry(main)> self.send :self
=> "self is self?"