Rails - Apr 2009 - Convert string to hexadecimal (preserving meaning)

I''m using a charting library that takes color values in hex, so white
would be 0xffffff. This is a number, not a string, so doing something
like "0x" + my_color_variable wouldn''t work.

If I have a variable from user input that is "FFFFFF", how can I
convert
it to the hex number 0xffffff?
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On Apr 16, 4:47 pm, Jack Bauer
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> I''m using a charting library that takes color values in hex, so
white
> would be 0xffffff. This is a number, not a string, so doing something
> like "0x" + my_color_variable wouldn''t work.
>
> If I have a variable from user input that is "FFFFFF", how can I
convert
> it to the hex number 0xffffff?
the to_i method on string takes an optional argument (the base to
use).

Fred
> --
> Posted viahttp://www.ruby-forum.com/.
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Frederick Cheung wrote:
> 
> the to_i method on string takes an optional argument (the base to
> use).
> 
> Fred
Yes, but it doesn''t convert it the way I need it to. What I mean is:

"FFFFFF".to_i(base=16) # => 16777215

I need it to be more like this:

"FFFFFF".whatever_magic_method # => 0xFFFFFF
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Jack Bauer wrote:
[...]
> 
> Yes, but it doesn''t convert it the way I need it to. What I mean
is:
> 
> "FFFFFF".to_i(base=16) # => 16777215
> 
> I need it to be more like this:
> 
> "FFFFFF".whatever_magic_method # => 0xFFFFFF
So wrap it:

class String
  def parse_hex
    self.to_i 16
  end
end

What''s the big deal?

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
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On Apr 16, 5:20 pm, Jack Bauer
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Frederick Cheung wrote:
>
> Yes, but it doesn''t convert it the way I need it to. What I mean
is:
>
> "FFFFFF".to_i(base=16) # => 16777215
>
> I need it to be more like this:
>
> "FFFFFF".whatever_magic_method # => 0xFFFFFF
Those are exactly the same integer - the console just shows them to
you in base 10 by default. to_s takes a similar base argument if you
need to get a string out of it again.

Fred
> --
> Posted viahttp://www.ruby-forum.com/.
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Jack Bauer wrote:
> I need it to be more like this:
> 
> "FFFFFF".whatever_magic_method # => 0xFFFFFF
I think at this point, the issue is that you need to deal with how to 
display the integer, not conver ti.
"FF".to_i(16) produces the INTEGER: 255 which is the same as 0xFF.

So, if you want to display the INTEGER 255 as hex, use either printf 
"0x%0x" or to_s(16). For instance:

Ruby code:
s = "0xFF"
puts "Convert string [#{s}] to an integer:"
n = s.to_i(16)
puts "normal puts: #{n}"
printf "printf in hex: 0x%x\n", n
puts "using to_s(16): #{n.to_s(16)}"

Outputs:
Convert string [0xFF] to an integer:
normal puts: 255
printf in hex: 0xff
using to_s(16): ff

Hope that helps.
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Well , i just wanted to say a big THANKS!!!

to Joshua for the solution,

and Jack for posting up this problem which was the same as i was
facing..

This post came up when i googled for it. And the solution mentioned
above solved my problem..

Thanks a ton!! to both of you :)



Joshua Ball wrote in post #806177:
> Jack Bauer wrote:
>
>> I need it to be more like this:
>>
>> "FFFFFF".whatever_magic_method # => 0xFFFFFF
>
> I think at this point, the issue is that you need to deal with how to
> display the integer, not conver ti.
> "FF".to_i(16) produces the INTEGER: 255 which is the same as
0xFF.
>
> So, if you want to display the INTEGER 255 as hex, use either printf
> "0x%0x" or to_s(16). For instance:
>
> Ruby code:
> s = "0xFF"
> puts "Convert string [#{s}] to an integer:"
> n = s.to_i(16)
> puts "normal puts: #{n}"
> printf "printf in hex: 0x%x\n", n
> puts "using to_s(16): #{n.to_s(16)}"
>
> Outputs:
> Convert string [0xFF] to an integer:
> normal puts: 255
> printf in hex: 0xff
> using to_s(16): ff
>
> Hope that helps.
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