I am coming to Ruby from LISP where I was more competent when it came
to symbol
manipulation I have spent some time trying to solve this problem
and figure it’s my
general lack of deep knowledge ala Ruby that keeps me from seeing an
“easy” solution.
With that said, I apologize if this has been answered and I missed
it.
I have a string in a variable.
foo = “bobo”
I want to use foo to access an array called bobo. I will have bobo
defined already.
Is there a way to do this?
Take foo and use it to access bobo[2], for example.
I thought about turning foo into a symbol, but that wasn’t the way.
And, I think there
should be a way to ask Ruby to return an object via its string name,
but I am
missing the way.
Thanks for the folks that mentioned eval—I thought of that after the
posting but
assumed that, as in LISP, there might be a better way to accomplish
it
It’s nice to see more similarities between LISP and Ruby.
Thanks for the folks that mentioned eval—I thought of that after the
posting but assumed that, as in LISP, there might be a better way
to accomplish
it
It’s nice to see more similarities between LISP and Ruby.
I don’t know whether or not you will think this better than using
‘eval’, but in Ruby this kind of indirect reference problem can often
be handled by introducing a hash. For example,
a = %w{ one two three four five }
b = %w{ six seven eight nine }
h = {}
h['a'] = a
h['b'] = b
foo = 'a'
h[foo][2] # => "three"
foo = 'b'
h[foo][2] # => "eight"
I want to use foo to access an array called bobo. I will have bobo
defined already.
This type of question seems to come up periodically on the list but
I never seem to run into in while coding. I tend to think that in most
(but not all) cases the need to reach for eval indicates some larger
design issue.
In your case, I would ask why you are resorting to using several local
variables that you need to distinguish by name rather than simply using
a hash to organize things?
Thanks for the folks that mentioned eval—I thought of that after the
posting but
assumed that, as in LISP, there might be a better way to accomplish
it
Are you thinking about Ma****, do not mention it anymore on this list
Well it is not really the way of Ruby.
It’s nice to see more similarities between LISP and Ruby.
kenny
There is if you can get away from the local variable as somebody
mentioned without sharing his wisdom with us
On Tue, Feb 20, 2007 at 09:20:13AM +0900, kenbo wrote:
I have a string in a variable.
foo = “bobo”
I want to use foo to access an array called bobo. I will have bobo
defined already.
Is there a way to do this?
eval() might be what you’re looking for. You can use eval to return the
array then index in to it. Here’s an example from:
irb(main):001:0> awesome_array = %w{ one two three four five }
=> [“one”, “two”, “three”, “four”, “five”]
irb(main):002:0> foo = ‘awesome_array’
=> “awesome_array”
irb(main):003:0> puts eval(foo)[1]
two
=> nil
irb(main):004:0>
It’s very unusual to need to dynamically reference a local variable. In
Ruby, local variables usually are highly, er, localized. An instance
variable is much more frequently used in the way you describe, and you
can access it, as Robert says, like so:
I have spent some time trying to solve this problem
