Setter doesn't work with -=, +=, etc? [duplicate]

Answer 1

Because var is nil. you need to assign some value to it first

def test
    puts var
    var=0 
    var -= 1 # <<< crash: undefined method for nil class
    puts var
    var=0
    var = var - 1 # <<< crash: undefined method for nil class
    puts var
  end