Self Generating Class Attributes.ipynb

{
 "metadata": {
  "language": "Julia",
  "name": "Self Generating Class Attributes"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "import Base: getindex, haskey, setindex!",
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "type Context\n    _attr::Dict{Symbol,Any}\n    Context() = new(Dict{Symbol,Any}())\n    Context(attr::Dict{Symbol,Any}) = new(attr)\nend",
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "function getindex(context::Context, key::Symbol)\n    if haskey(context._attr, key)\n        return context._attr[key]\n    else\n        # TODO: Keep track of what attributes we are generating on \n        #       so that we don't end up in an infinite loop.\n        try\n            generate_fn = eval(symbol(string(\"generate_\", key)))\n            context._attr[key] = generate_fn(context)\n            return context._attr[key]\n        catch exception\n            error(\"Error getting attribute '$key': $exception\")\n        end\n    end\nend\n\nfunction setindex!(context::Context, value::Any, key::Symbol)\n    context._attr[key] = value\nend\n\nfunction haskey(context::Context, key::Symbol)\n    return haskey(context._attr, key)\nend",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 3,
       "text": "haskey (generic function with 5 methods)"
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "function generate_foo(context::Context)\n    return \"bar\"\nend",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 4,
       "text": "generate_foo (generic function with 1 method)"
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "c = Context()",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 5,
       "text": "Context(Dict{Symbol,Any}())"
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "c[:foo]",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 6,
       "text": "\"bar\""
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "c[:Foo]",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "ename": "LoadError",
       "evalue": "Error getting attribute 'Foo': ErrorException(\"generate_Foo not defined\")\nat In[7]:1",
       "output_type": "pyerr",
       "traceback": [
        "Error getting attribute 'Foo': ErrorException(\"generate_Foo not defined\")\nat In[7]:1",
        " in error at error.jl:21",
        " in getindex at In[3]:10"
       ]
      }
     ],
     "prompt_number": 7
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "c[:a] = 2",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 8,
       "text": "2"
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "generate_b(context::Context) = 10 * context[:a]",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 10,
       "text": "generate_b (generic function with 1 method)"
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "c[:b]",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 11,
       "text": "20"
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "haskey(c, :b)",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 12,
       "text": "true"
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "haskey(c, :c)",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 13,
       "text": "false"
      }
     ],
     "prompt_number": 13
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "",
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}