Ruby convert Object to Hash
Let's say I have a Gift
object with @name = "book"
& @price = 15.95
. What's the best way to convert that to t开发者_运维问答he Hash {name: "book", price: 15.95}
in Ruby, not Rails (although feel free to give the Rails answer too)?
Just say (current object) .attributes
.attributes
returns a hash
of any object
. And it's much cleaner too.
class Gift
def initialize
@name = "book"
@price = 15.95
end
end
gift = Gift.new
hash = {}
gift.instance_variables.each {|var| hash[var.to_s.delete("@")] = gift.instance_variable_get(var) }
p hash # => {"name"=>"book", "price"=>15.95}
Alternatively with each_with_object
:
gift = Gift.new
hash = gift.instance_variables.each_with_object({}) { |var, hash| hash[var.to_s.delete("@")] = gift.instance_variable_get(var) }
p hash # => {"name"=>"book", "price"=>15.95}
Implement #to_hash
?
class Gift
def to_hash
hash = {}
instance_variables.each { |var| hash[var.to_s.delete('@')] = instance_variable_get(var) }
hash
end
end
h = Gift.new("Book", 19).to_hash
Gift.new.instance_values # => {"name"=>"book", "price"=>15.95}
You can use as_json
method. It'll convert your object into hash.
But, that hash will come as a value to the name of that object as a key. In your case,
{'gift' => {'name' => 'book', 'price' => 15.95 }}
If you need a hash that's stored in the object use as_json(root: false)
. I think by default root will be false. For more info refer official ruby guide
http://api.rubyonrails.org/classes/ActiveModel/Serializers/JSON.html#method-i-as_json
For Active Record Objects
module ActiveRecordExtension
def to_hash
hash = {}; self.attributes.each { |k,v| hash[k] = v }
return hash
end
end
class Gift < ActiveRecord::Base
include ActiveRecordExtension
....
end
class Purchase < ActiveRecord::Base
include ActiveRecordExtension
....
end
and then just call
gift.to_hash()
purch.to_hash()
class Gift
def to_hash
instance_variables.map do |var|
[var[1..-1].to_sym, instance_variable_get(var)]
end.to_h
end
end
If you are not in an Rails environment (ie. don't have ActiveRecord available), this may be helpful:
JSON.parse( object.to_json )
You can write a very elegant solution using a functional style.
class Object
def hashify
Hash[instance_variables.map { |v| [v.to_s[1..-1].to_sym, instance_variable_get v] }]
end
end
Recursively convert your objects to hash using 'hashable' gem (https://rubygems.org/gems/hashable) Example
class A
include Hashable
attr_accessor :blist
def initialize
@blist = [ B.new(1), { 'b' => B.new(2) } ]
end
end
class B
include Hashable
attr_accessor :id
def initialize(id); @id = id; end
end
a = A.new
a.to_dh # or a.to_deep_hash
# {:blist=>[{:id=>1}, {"b"=>{:id=>2}}]}
You should override the inspect
method of your object to return the desired hash, or just implement a similar method without overriding the default object behaviour.
If you want to get fancier, you can iterate over an object's instance variables with object.instance_variables
Might want to try instance_values
. That worked for me.
To plagiarize @Mr. L in a comment above, try @gift.attributes.to_options
.
You can use symbolize_keys
and in-case you have nested attributes we can use deep_symbolize_keys
:
gift.as_json.symbolize_keys => {name: "book", price: 15.95}
Produces a shallow copy as a hash object of just the model attributes
my_hash_gift = gift.attributes.dup
Check the type of the resulting object
my_hash_gift.class
=> Hash
If you need nested objects to be converted as well.
# @fn to_hash obj {{{
# @brief Convert object to hash
#
# @return [Hash] Hash representing converted object
#
def to_hash obj
Hash[obj.instance_variables.map { |key|
variable = obj.instance_variable_get key
[key.to_s[1..-1].to_sym,
if variable.respond_to? <:some_method> then
hashify variable
else
variable
end
]
}]
end # }}}
Gift.new.attributes.symbolize_keys
To do this without Rails, a clean way is to store attributes on a constant.
class Gift
ATTRIBUTES = [:name, :price]
attr_accessor(*ATTRIBUTES)
end
And then, to convert an instance of Gift
to a Hash
, you can:
class Gift
...
def to_h
ATTRIBUTES.each_with_object({}) do |attribute_name, memo|
memo[attribute_name] = send(attribute_name)
end
end
end
This is a good way to do this because it will only include what you define on attr_accessor
, and not every instance variable.
class Gift
ATTRIBUTES = [:name, :price]
attr_accessor(*ATTRIBUTES)
def create_random_instance_variable
@xyz = 123
end
def to_h
ATTRIBUTES.each_with_object({}) do |attribute_name, memo|
memo[attribute_name] = send(attribute_name)
end
end
end
g = Gift.new
g.name = "Foo"
g.price = 5.25
g.to_h
#=> {:name=>"Foo", :price=>5.25}
g.create_random_instance_variable
g.to_h
#=> {:name=>"Foo", :price=>5.25}
I started using structs to make easy to hash conversions. Instead of using a bare struct I create my own class deriving from a hash this allows you to create your own functions and it documents the properties of a class.
require 'ostruct'
BaseGift = Struct.new(:name, :price)
class Gift < BaseGift
def initialize(name, price)
super(name, price)
end
# ... more user defined methods here.
end
g = Gift.new('pearls', 20)
g.to_h # returns: {:name=>"pearls", :price=>20}
Following Nate's answer which I haven't been able to compile:
Option 1
class Object
def to_hash
instance_variables.map{ |v| Hash[v.to_s.delete("@").to_sym, instance_variable_get(v)] }.inject(:merge)
end
end
And then you call it like that:
my_object.to_hash[:my_variable_name]
Option 2
class Object
def to_hash
instance_variables.map{ |v| Hash[v.to_s.delete("@"), instance_variable_get(v)] }.inject(:merge)
end
end
And then you call it like that:
my_object.to_hash["my_variable_name"]
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