# Programming Ruby ### The Pragmatic Programmer's Guide
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module Marshal

### Index:

dump load restore

The marshaling library converts collections of Ruby objects into a byte stream, allowing them to be stored outside the currently active script. This data may subsequently be read and the original objects reconstituted. Marshaling is described starting on page 268.

Some objects cannot be dumped: if the objects to be dumped include bindings, procedure objects, instances of class `IO`, or singleton objects, a `TypeError` will be raised.

If your class has special serialization needs (for example, if you want to serialize in some specific format), or if it contains objects that would otherwise not be serializable, you can implement your own serialization strategy by defining two methods, `_dump` and `_load`:

Method Type | Signature | Returns
Instance | _dump(aDepth) | Returns a `String`
Class | _load(aString) | Returns a reconstituted `Object`

The instance method `_dump` should return a `String` object containing all the information necessary to reconstitute objects of this class and all referenced objects up to a maximum depth of aDepth (a value of -1 should disable depth checking). The class method `_load` should take a `String` and return an object of this class.

class methods
dump | dump( anObject [, anIO ] , limit=--1 ) -> anIO
|  | Serializes anObject and all descendent objects. If anIO is specified, the serialized data will be written to it, otherwise the data will be returned as a `String`. If limit is specified, the traversal of subobjects will be limited to that depth. If limit is negative, no checking of depth will be performed.
    class Klass
      def initialize(str)
        @str = str
      end
      def sayHello
        @str
      end
    end
`o = Klass.new("hello\n")`
`data = Marshal.dump(o)`
`obj = Marshal.load(data)`
`obj.sayHello` | » | `"hello\n"`
load | load( from [, aProc ] ) -> anObject
|  | Returns the result of converting the serialized data in from into a Ruby object (possibly with associated subordinate objects). from may be either an instance of `IO` or an object that responds to `to_str`. If proc is specified, it will be passed each object as it is deserialized.
restore | restore( from [, aProc ] ) -> anObject
|  | A synonym for `Marshal::load` .

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Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/)).

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