Ruby Kernel: caller

caller(start=1, length=nil)
→ array or nil

Returns the current execution stack—an array containing strings in the form file:line or file:line: in `method’.

The optional start parameter determines the number of initial stack entries to omit from the top of the stack. A second optional length parameter can be used to limit how many entries are returned from the stack. Returns nil if start is greater than the size of current execution stack. Optionally you can pass a range, which will return an array containing the entries within the specified range.
[ruby-doc.org]

def a(skip)
  caller(skip)
end
def b(skip)
  a(skip)
end
def c(skip)
  b(skip)
end
c(0)   #=> ["prog:2:in `a'", "prog:5:in `b'", "prog:8:in `c'", "prog:10:in `<main>'"]
c(1)   #=> ["prog:5:in `b'", "prog:8:in `c'", "prog:11:in `<main>'"]
c(2)   #=> ["prog:8:in `c'", "prog:12:in `<main>'"]
c(3)   #=> ["prog:13:in `<main>'"]
c(4)   #=> []
c(5)   #=> nil

DataMapper Important Rules

belongs_to :post  # defaults to :required => true

belongs_to relationships will be required by default (the parent resource must exist in order for the child to be valid). You can make the parent resource optional by passing :required => false as an option to belongs_to.

Ruby – Convert Object to Hash

What’s the best way to convert an Object to Hash in Ruby?

class Gift
  def initialize
    @name = "book"
    @price = 15.95
  end
end

gift = Gift.new
hash = {}
gift.instance_variables.each {|var| hash[var.to_s.delete("@")] = gift.instance_variable_get(var) }
p hash # => {"name"=>"book", "price"=>15.95}

Source: Stackoverflow