# One field maintaining (boolean) state of multiple items

**URL:** <https://www.ruby-forum.com/t/one-field-maintaining-boolean-state-of-multiple-items/77693>\
**Category:** Ruby\
**Created:** [November 29, 2006, 7:51pm UTC](https://www.ruby-forum.com/t/one-field-maintaining-boolean-state-of-multiple-items/77693 "2006-11-29T19:51:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![el-gato](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e0b2c6/32.png) [@el-gato](https://www.ruby-forum.com/u/el-gato)\
**Post date:** [November 29, 2006, 7:51pm UTC](https://www.ruby-forum.com/t/one-field-maintaining-boolean-state-of-multiple-items/77693/1 "2006-11-29T19:51:59Z")

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I have a friend who posed a question to me about how to maintain the  
state of a few boolean values (radio buttons to be specific) in one  
(integer) database column. It really is more of a curious question than  
anything else, as he could simply add more columns to the table to avoid  
even thinking about it, but for the sake of fun he didn’t. So, let’s  
say you have three boolean values that you need to store in one field,  
and you must be able to determine what the state is (true/false) of any  
of the 3 values at any time. How would you do this? My immediate  
thought went to bit shifting or some other bit operations, but I’ve  
never really used anything like that before, so I’m a little stuck on  
this. Thoughts?

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<div class="post-metadata">

**Author:** ![el-gato](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e0b2c6/32.png) [@el-gato](https://www.ruby-forum.com/u/el-gato)\
**Post date:** [November 29, 2006, 10:57pm UTC](https://www.ruby-forum.com/t/one-field-maintaining-boolean-state-of-multiple-items/77693/2 "2006-11-29T22:57:15Z")

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El Gato wrote:

> this. Thoughts?  
> Given an integer that you want to disassemble into binary bits:

v = 15

Let’s create an array that will contain the values of the bits:

array = []

Now let’s scan the integer’s bits:

1.upto(8) do  
array \<\< (v & 1 == 1)  
v \>\>= 1  
end

Now the array contains 8 boolean (true/false) values corresponding to  
the  
low 8 bits in the original integer.

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<div class="post-metadata">

**Author:** ![el-gato](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e0b2c6/32.png) [@el-gato](https://www.ruby-forum.com/u/el-gato)\
**Post date:** [November 29, 2006, 11:53pm UTC](https://www.ruby-forum.com/t/one-field-maintaining-boolean-state-of-multiple-items/77693/3 "2006-11-29T23:53:37Z")

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Paul L. wrote:

> > thought went to bit shifting or some other bit operations, but I’ve
> 
> Now let’s scan the integer’s bits:
> 
> 1.upto(8) do  
> array \<\< (v & 1 == 1)  
> v \>\>= 1  
> end
> 
> Now the array contains 8 boolean (true/false) values corresponding to the  
> low 8 bits in the original integer.

irb(main):003:0\> v = 15; (0…7).map {|i| v[i]}  
=\> [1, 1, 1, 1, 0, 0, 0, 0]

For more info, ri ‘Fixnum#[]’. But there is no #[]= (makes sense if you  
think about it).

Another idea, storing the data in a string of length 1:

require ‘bit-struct’ # [BitStruct](http://redshift.sourceforge.net/bit-struct)

class Bits \< BitStruct  
unsigned :bit0, 1  
unsigned :bit1, 1  
unsigned :bit2, 1  
unsigned :bit3, 1  
unsigned :bit4, 1  
unsigned :bit5, 1  
unsigned :bit6, 1  
unsigned :bit7, 1  
end

b = Bits.new

b.bit3 = 1  
p b.bit3 # ==\> 1  
p b.bit4 # ==\> 0