ruby - How to exclude an instance variable from marshal dump -

my object contains instance variable point file object amongst several other attributes. because of marshal cannot serialize it. how can write bespoke dump method exclude instance variable?

class area   attr_accessor :area   attr_reader :several_other_attributes   ........    def initialize(name)     @area = name     @several_other_attributes = ....      @log = file.open( 'test.log', 'w')   end end 

you can write marshal_dump , marshal_load method marshals specified number of instance variables. here's generic example of do:

class marshaltest   attr_reader :foo, :bar, :baz, :t   unmarshaled_variables = [:@foo, :@bar]    def initialize(foo = nil, bar = nil, baz = nil, t = nil)     @foo = foo     @bar = bar     @baz = baz     @t = t   end    def marshal_dump     instance_variables.reject{|m| unmarshaled_variables.include? m}.inject({}) |vars, attr|       vars[attr] = instance_variable_get(attr)       vars     end   end    def marshal_load(vars)     vars.each |attr, value|       instance_variable_set(attr, value) unless unmarshaled_variables.include?(attr)     end   end end 

example usage:

1.9.3-p550 :026 > m = marshaltest.new(1, 2, 3, 4)  => #<marshaltest:0x007ff73194cae8 @foo=1, @bar=2, @baz=3, @t=4> 1.9.3-p550 :027 > m.foo  => 1 1.9.3-p550 :028 > m.bar  => 2 1.9.3-p550 :029 > m.baz  => 3 1.9.3-p550 :030 > m.t  => 4 1.9.3-p550 :031 > s = marshal.dump(m)  => "\x04\bu:\x10marshaltest{\a:\t@bazi\b:\a@ti\t" 1.9.3-p550 :032 > n = marshal.load(s)  => #<marshaltest:0x007ff73112b828 @baz=3, @t=4> 1.9.3-p550 :033 > n.foo  => nil 1.9.3-p550 :034 > n.bar  => nil 1.9.3-p550 :035 > n.baz  => 3 1.9.3-p550 :036 > n.t  => 4 

as can see, instance variables foo , bar ignored in marshaling/unmarshaling.