For the JSON library to be available, you may have to install libjson-ruby from your package manager.
To use the 'json' library:
require 'json'
To convert an object to JSON (these 3 ways are equivalent):
JSON.dump object #returns a JSON string
JSON.generate object #returns a JSON string
object.to_json #returns a JSON string
To convert JSON text to an object (these 2 ways are equivalent):
JSON.load string #returns an object
JSON.parse string #returns an object
It will be a bit more difficult for objects from your own classes. For the following class, to_json will produce something like "\"#<A:0xb76e5728>\"".
class A
def initialize a=[1,2,3], b='hello'
@a = a
@b = b
end
end
This probably isn't desirable. To effectively serialise your object as JSON, you should create your own to_json method. To go with this, a from_json class method would be useful. You could extend your class like so:
class A
def to_json
{'a' => @a, 'b' => @b}.to_json
end
def self.from_json string
data = JSON.load string
self.new data['a'], data['b']
end
end
You could automate this by inheriting from a 'JSONable' class:
class JSONable
def to_json
hash = {}
self.instance_variables.each do |var|
hash[var] = self.instance_variable_get var
end
hash.to_json
end
def from_json! string
JSON.load(string).each do |var, val|
self.instance_variable_set var, val
end
end
end
Then you can use object.to_json to serialise to JSON and object.from_json! string to copy the saved state that was saved as the JSON string to the object.