Convert Ruby Hash into YAML

Question

I need to convert a hash like the one provided below into readable YAML. It looks like I can feed YAML::load a string, but I think I need to convert it first into something like this:

hostname1.test.com:
  public: 51
  private: 10

{"hostname1.test.com"=>
   {"public"=>"51", "private"=>"10"},
 "hostname2.test.com"=>
   {"public"=>"192", "private"=>"12"}
}

I'm not sure exactly how to do that conversion into that string effectively though.

I looked through the HASH documentation and couldn't find anything for to_yaml. I found it by searching for to_yaml which becomes available when you require yaml. I also tried to use the Enumerable method collect but got confused when I needed to iterate through the value (another hash).

I'm trying to use "Converting hash to string in Ruby" as a reference. My thought was then to feed that into YAML::load and that would generate the YAML I wanted.

Solution 1

Here's how I'd do it:

require 'yaml'

HASH_OF_HASHES = {
  "hostname1.test.com"=> {"public"=>"51", "private"=>"10"},
  "hostname2.test.com"=> {"public"=>"192", "private"=>"12"}
}

ARRAY_OF_HASHES = [
  {"hostname1.test.com"=> {"public"=>"51", "private"=>"10"}},
  {"hostname2.test.com"=> {"public"=>"192", "private"=>"12"}}
]

puts HASH_OF_HASHES.to_yaml
puts
puts ARRAY_OF_HASHES.to_yaml

Which outputs:

---
hostname1.test.com:
  public: '51'
  private: '10'
hostname2.test.com:
  public: '192'
  private: '12'

---
- hostname1.test.com:
    public: '51'
    private: '10'
- hostname2.test.com:
    public: '192'
    private: '12'

---

The Object class has a to_yaml method. I used that and it generated the YAML file correctly.

No, it doesn't.

This is from a freshly opened IRB session:

Object.instance_methods.grep(/to_yaml/)
=> []
require 'yaml'
=> true
Object.instance_methods.grep(/to_yaml/)
=> [:psych_to_yaml, :to_yaml, :to_yaml_properties]

Solution 2

You can use the to_yaml method on a hash for this I believe after you require yaml

Solution 3

You can use YAML.dump:

YAML.dump(a: 2, b: 1)
=> "---\n:a: 2\n:b: 1\n

One advantage of YAML.dump over to_yaml is that it's easier to infer what the code is doing because most people read from left to right.

Comments

[PJP]

Hash doesn't have a to_yaml method.

[PJP]

Object does not have a to_yaml method. Only the YAML class has it, and it extends other classes when it's required.