tryme.rb

class Tryme
  def call1
    target = 'boom'
    puts target
  end

  def call2
    self.target = 'boom'
    puts target
  end

  def target=(value)
    puts "target= was called with #{value}"
  end

  def target
    puts "target was called"
  end
end

tm = Tryme.new

puts "CALL 1"
tm.call1

puts "CALL 2"
tm.call2

% ruby -v
ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin15]
% ruby tryit.rb
% ruby tryit.rb
CALL 1
boom
CALL 2
target= was called with boom
target was called