Ruby self

it has one and only has one self, to point the current or default object accessible.

at top level

self points to main

p self          #==> main
  

def m
    p self      #==> main
end
  

inside class or module

self will be the class or module object

class S
    p self          #==> S
    module M
        p self      #==> S::M
    end
end
  

class S
    def m
        p self
    end
end
s = S.new
s.m         #==> #<S:0x1229181>     means the instance of S
  

in singleton method

self inside singleton method means the object owns it.

class S
    def S.m
        p self      #==> S      who owns method m
    end
end
  

summary

graph LR A((self)) B[[at top-level]] C[[in class]] D[[in module]] E[[in singleton]] A --> B B -- codes chunk --> main B -- method --> main A --> C --> CC(class) A --> D --> DD(module) A --> E --> EE(owner)