Ruby Convert String to Hash

Question

I'm storing configuration data in hashes written in flat files. I want to import the hashes into my Class so that I can invoke corresponding methods.

example.rb

{ 
  :test1 => { :url => 'http://www.google.com' }, 
  :test2 => {
    { :title => 'This' } => {:failure => 'sendemal'}
  }
}

simpleclass.rb

class Simple
  def initialize(file_name)
    # Parse the hash
    file = File.open(file_name, "r")
    @data = file.read
    file.close
  end

  def print
    @data
  end

a = Simple.new("simpleexample.rb")
b = a.print
puts b.class   # => String

How do I convert any "Hashified" String into an actual Hash?

I would store it as JSON, read the file and use JSON.parse — 23tux
– 23tux, Commented Nov 12, 2016 at 20:09
use YML (yaml) or JSON to store hash in file and read it in ruby file as its actual data structure. — Sivalingam
– Sivalingam, Commented Nov 12, 2016 at 20:10

David Grayson · Accepted Answer · 2016-11-12 20:11:18Z

13

You can use eval(@data), but really it would be better to use a safer and simpler data format like JSON.

answered Nov 12, 2016 at 20:11

David Grayson

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Comments

Amol Udage · Accepted Answer · 2017-01-24 06:15:52Z

4

You can try YAML.load method

Example:

 YAML.load("{test: 't_value'}")

This will return following hash.

 {"test"=>"t_value"}

You can also use eval method

Example:

 eval("{test: 't_value'}")

This will also return same hash

  {"test"=>"t_value"}

Hope this will help.

answered Jan 24, 2017 at 6:15

Amol Udage

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Comments

Edvaldo Silva de Almeida Jr · Accepted Answer · 2016-11-12 20:21:29Z

2

I would to this using the json gem.

In your Gemfile you use

gem 'json'

and then run bundle install.

In your program you require the gem.

require 'json'

And then you may create your "Hashfield" string by doing:

hash_as_string = hash_object.to_json

and write this to your flat file.

Finally, you may read it easily by doing:

my_hash = JSON.load(File.read('your_flat_file_name'))

This is simple and very easy to do.

edited Nov 12, 2016 at 20:21

answered Nov 12, 2016 at 20:13

Edvaldo Silva de Almeida Jr

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Comments

Cary Swoveland · Accepted Answer · 2016-11-15 05:01:18Z

Should it not be clear, it is only the hash that must be contained in a JSON file. Suppose that file is "simpleexample.json":

puts File.read("simpleexample.json")
  # #{"test1":{"url":"http://www.google.com"},"test2":{"{:title=>\"This\"}":{"failure":"sendemal"}}}

The code can be in a normal Ruby source file, "simpleclass.rb":

puts File.read("simpleclass.rb")
  # class Simple
  #   def initialize(example_file_name)
  #     @data = JSON.parse(File.read(example_file_name))
  #   end
  #   def print
  #     @data
  #   end
  # end

Then we can write:

require 'json'
require_relative "simpleclass"

a = Simple.new("simpleexample.json")
  #=> #<Simple:0x007ffd2189bab8 @data={"test1"=>{"url"=>"http://www.google.com"},
  #     "test2"=>{"{:title=>\"This\"}"=>{"failure"=>"sendemal"}}}> 
a.print
  #=> {"test1"=>{"url"=>"http://www.google.com"},
  #    "test2"=>{"{:title=>\"This\"}"=>{"failure"=>"sendemal"}}} 
a.class
  #=> Simple

To construct the JSON file from the hash:

h = { :test1=>{ :url=>'http://www.google.com' },
      :test2=>{ { :title=>'This' }=>{:failure=>'sendemal' } } }

we write:

File.write("simpleexample.json", JSON.generate(h))
  #=> 95

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