# Dynamically create a hash of a objects variables values

**URL:** <https://www.ruby-forum.com/t/dynamically-create-a-hash-of-a-objects-variables-values/153397>\
**Category:** Ruby\
**Created:** [November 16, 2008, 10:49am UTC](https://www.ruby-forum.com/t/dynamically-create-a-hash-of-a-objects-variables-values/153397 "2008-11-16T10:49:20Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![scudco](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/aca169/32.png) [@scudco](https://www.ruby-forum.com/u/scudco)\
**Post date:** [November 16, 2008, 10:49am UTC](https://www.ruby-forum.com/t/dynamically-create-a-hash-of-a-objects-variables-values/153397/1 "2008-11-16T10:49:20Z")

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Tried my best to make this title as informative as possible but its  
ended up a bit cryptic.

Say I have a class Record which represents records in a database and a  
particular object has these instance variables

@a = 1  
@b = 2  
@c = 3

Id like to be able to create a hash that has the varible names i.e.  
a,b,c as keys and then their values as the hash values.

e.g. {a=\>1, b=\>2, c=\>3}

HOWEVER i would like this to be done dynamically so that if I add or  
remove variables to my class definition the conversion method will  
include these without me having to hard code them in the conversion  
function.

Is this possible and if so what topic would this come under in a book?  
Any tips or code snippets would be greatly appreciated.

---

<div class="post-metadata">

**Author:** ![scudco](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/aca169/32.png) [@scudco](https://www.ruby-forum.com/u/scudco)\
**Post date:** [November 16, 2008, 10:56am UTC](https://www.ruby-forum.com/t/dynamically-create-a-hash-of-a-objects-variables-values/153397/2 "2008-11-16T10:56:42Z")

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Alle Sunday 16 November 2008, Adam A. ha scritto:

> Is this possible and if so what topic would this come under in a book?  
> Any tips or code snippets would be greatly appreciated.

The method instance\_variables returns an array containing the names of  
all the  
instance variables of the receiver (including the leading @). The  
instance\_variable\_get method, instead, returns the value of the instance  
variable whose name is passed as argument. To do what you want, you can  
do the  
following:

res = {}  
instance\_variables.each{|v| res[v[1…-1]] = instance\_variable\_get(v)}  
res

Here’s a full example:

class C  
def initialize  
@x = 1  
@y = 2  
@z = 3  
end  
def create\_hash  
res = {}  
instance\_variables.each{|v| res[v[1…-1]] =  
instance\_variable\_get(v)}  
res  
end  
end

p C.new.create\_hash  
=\> {“x”=\>1, “y”=\>2, “z”=\>3}

I hope this helps

Stefano

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<div class="post-metadata">

**Author:** ![scudco](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/aca169/32.png) [@scudco](https://www.ruby-forum.com/u/scudco)\
**Post date:** [November 16, 2008, 11:05am UTC](https://www.ruby-forum.com/t/dynamically-create-a-hash-of-a-objects-variables-values/153397/3 "2008-11-16T11:05:01Z")

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Wow stefano thats perfect. Ill research that method more on the ruby  
core website but what you wrote seems to be exactly what i wanted.

Thanks again.

---

<div class="post-metadata">

**Author:** ![scudco](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/aca169/32.png) [@scudco](https://www.ruby-forum.com/u/scudco)\
**Post date:** [November 16, 2008, 12:45pm UTC](https://www.ruby-forum.com/t/dynamically-create-a-hash-of-a-objects-variables-values/153397/4 "2008-11-16T12:45:36Z")

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On 16.11.2008 10:46, Adam A. wrote:

> Is this possible and if so what topic would this come under in a book?  
> Any tips or code snippets would be greatly appreciated.

Depends on what you want to do with the Hash but Struct may help you:

irb(main):001:0\> S = Struct.new :a, :b, :c  
=\> S  
irb(main):002:0\> s = S.new 1,2,3  
=\> #  
irb(main):003:0\> s[:a]  
=\> 1  
irb(main):004:0\> s[:b]  
=\> 2  
irb(main):005:0\> s[:c]=100  
=\> 100  
irb(main):006:0\> s  
=\> #  
irb(main):007:0\>

If you want to add additional methods to the Struct you can do

S = Struct.new :a, :b, :c do  
def some\_method  
(a + b) \* c  
end  
end

Kind regards

robert