W1D2 - References, object_id, and mutability

object_ids_and_mutability.rb

## Be careful when referencing mutable objects

a = {}           # => {}
b = a            # => {}
a.object_id      # => 70132601471180
b.object_id      # => 70132601471180
a[:foo] = 'bar'  # => "bar"
b                # => {:foo=>"bar"}      # Woah!



## Fixnums are a special case, because numbers are immutable.

x = 2       # => 2
y = x       # => 2
x.object_id # => 5   
y.object_id # => 5    # Both x and y are referencing 
                      # the same Fixnum object

x += 1      # => 3
x.object_id # => 7    # The x reference now points to a different object.
y.object_id # => 5    # y still referencing the value 2