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POHow to marshal a class in Jruby which contains an array
 

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  1. POHow to marshal a class in Jruby which contains an array
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    <p>I have a 2D array containing many instances of a class. The class contains 4 arrays. I would like to save and load the 2D array to/from disk using Marshal. I have successfully used Marshal for this purpose with other 2D arrays containing classes, but those classes did not contain an array. Here is the definition of the class giving me trouble.</p> <pre><code>class Light attr_accessor :R,:G,:B,:A def initialize(i) @R = Array.new(4, i) @G = Array.new(4, i) @B = Array.new(4, i) @A = Array.new(4, i) end @R @G @B @A end </code></pre> <p>I have tried defining my own marshal functions in the Light class:</p> <pre><code>def marshal_dump {'R' =&gt; @R,'G' =&gt; @G,'B' =&gt; @B,'A' =&gt; @A} end def marshal_load(data) self.R = data['R'] self.G = data['G'] self.B = data['B'] self.A = data['A'] end </code></pre> <p>Here is the creation of the 2D array containing this class</p> <pre><code>def createLightMap(width,height) a = Array.new(width) { Light.new(0.7) } a.map! { Array.new(height) { Light.new(0.7) } } return a end @lightMap = createLightMap(10,10) </code></pre> <p>Here is how I save and load</p> <pre><code>#save File.open('lightData','w') do |file| Marshal.dump(@lightMap, file) end #load @lightMap = if File.exists?('lightData') File.open('lightData','w') do |file| Marshal.load(file) end else puts 'no light data found' end </code></pre> <p>Upon load, I receive the error "in 'load': dump format error (unlinked, index: -96) (Argument Error)"</p> <p>I have tried with and without custom dump/load marshal functions. I am using jruby 1.5.1, ruby 1.8.7</p>
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    1. USSpencer
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    1. COWhat are those bare `@R` etc. things for in the class declaration?
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      1. USDave Newton
    2. COThey're a habit leftover from coding in C++. I guess they're not really needed?
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      1. USSpencer
    3. COThey won't actually *do* anything; a class declaration executes in order. So the attr_accessors create access functions. The `def` declares the ctor function. The `@X` will just evaluate in the context of the *class*, not an instance, and be `nil` because they haven't been initialized to anything, and are totally meaningless at the class level (because they're instance variables).
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      1. USDave Newton
 

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