problems with ruby symbols in hash look-up -

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i'm trying create simple hash corresponding strings symbols (:student_number, :first_name, ...). i'm having issue retrieving data function though. here's function

snippet a

  def get_nice_column_name(col_symbol)     column_names = {        :first_name => "student's first name",       :last_name => "student's last name",        :email => "student's email",        :given_name => "student's given name"     }     return column_names[col_symbol]   end

here's how use it, not working:

snippet b

col_titles = [] params = {:first_name => 'true',            :last_name => 'true',            :email => 'true',            :given_name => 'true' }  params.each |key, value|   if ( value == 'true')     col_titles << get_nice_column_name(key)   end end

when col_titles, expect ["student's first name", "student's last name"], don't anything, [] empty array.

i thought weird tried printing out object_id of symbols (col_symbol in snippet a) , symbols in hash column_names, different object_ids. i'm wondering why different (they both present same symbols). if add function get_nice_column_name in snippet a:

    puts "col_symbol " + col_symbol.object_id.to_s + ", while :first_name " + (:first_name).object_id.to_s     puts "col_symbol " + col_symbol.object_id.to_s + ", while :last_name " + (:last_name).object_id.to_s     puts "col_symbol " + col_symbol.object_id.to_s + ", while :email " + (:email).object_id.to_s     puts "col_symbol " + col_symbol.object_id.to_s + ", while :given_name " + (:given_name).object_id.to_s

i in console 

col_symbol 98351040, while :first_name 1221688 col_symbol 98351040, while :last_name 580888 col_symbol 98351040, while :email 168888 col_symbol 98351040, while :given_name 1290648

983541040 doesn't match of {1221688, 580888, 168888, 1290648}. why get_nice_column_name useless ? because symbols different under hood?

thanks guys !

regards

if using ruby 1.9 bit more concise way it. 

column_names = {    :first_name => "student's first name",   :last_name  => "student's last name",   :email      => "student's email",   :given_name => "student's given name" }  params = {   :first_name => 'firstname',   :last_name  => 'lastname',   :email      => 'email',   :given_name => 'givenname' } col_titles = []  col_titles = column_names.values data = params.values_at(*column_names.keys)  col_titles # => ["student's first name", "student's last name", "student's email", "student's given name"] data # => ["firstname", "lastname", "email", "givenname"]

this takes advantage of ruby 1.9's new hash behavior, ruby remembers order of insertion , honor order when retrieving keys , values. can similar 1.8, you'd have define order of columns in array, use pull column headings , values of data instead of relying on column_names set order.


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