Is there an easy way to define a common interface for a group of unrelated objects?

Question

I've got a class that serializes data. I may want to serialize this data as JSON, or perhaps YAML. Can I cleanly swap YAML for JSON objects in this case? I was hoping I could do something like the following. Is it a pipe dream?

FORMATS = {
  :json => JSON,
  :yaml => YAML,
}

def serialize(data, format)
  FORMATS[format].serialize(data)
end

score 2 · Accepted Answer · answered Jul 31 '10 at 09:38

2

The code you have written should work just fine, provided that classes JSON and YAML both have class method called serialize. But I think the method that actually exists is #dump.

So, you would have:

require 'json'
require 'yaml'

FORMATS = {
  :json => JSON,
  :yaml => YAML,
}

def serialize(data, format)
  FORMATS[format].dump(data)
end

hash = {:a => 2}
puts serialize hash, :json
#=> {"a":2}

puts serialize hash, :yaml
#=> --- 
#=> :a: 2

answered Jul 31 '10 at 09:38

Mladen Jablanović

41,202
10
87
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Sweet. So they already have a common interface to serializing. Now, how about deserializing? – Blaine Lafreniere Jul 31 '10 at 15:41

score 0 · Answer 2 · answered Jul 31 '10 at 07:36

0

If JSON and YAML are classes or modules that already exist, you can write:

FORMATS = { :json => "JSON", :yaml => "YAML" }

def serialize(data, format)
    Kernel.const_get(FORMATS[format]).serialize(data) # 'serialize' is a class method in this case
end

answered Jul 31 '10 at 07:36

Daniel O'Hara

12,777
3
43
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Actually, you don't need to convert classes to and from string, the example OP has posted should work just fine, as classes are objects in Ruby. – Mladen Jablanović Jul 31 '10 at 09:32
It's true, but I thought class names are strings in the provided example. My fault. – Daniel O'Hara Jul 31 '10 at 09:35

Is there an easy way to define a common interface for a group of unrelated objects?

2 Answers2