How do I convert a String object into a Hash object

Question

I have a string which looks like a hash       key a   gt     key 1a   gt   value 1a    key 2a   gt   value 2a      key b   gt     key 1b   gt   value 1b         How do I get a Hash out of it  like      key a   gt     key 1a   gt   value 1a    key 2a   gt   value 2a      key b   gt     key 1b   gt   value 1b        The string can have any depth of nesting  It has all the properties how a valid Hash is typed in Ruby

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Maybe YAML load

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Quick and dirty method would be  eval     key a   gt     key 1a   gt   value 1a    key 2a   gt   value 2a      key b   gt     key 1b   gt   value 1b           But it has severe security implications  It executes whatever it is passed  you must be 110  sure  as in  at least no user input anywhere along the way  it would contain only properly formed hashes or unexpected bugs horrible creatures from outer space might start popping up

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Ran across a similar issue that needed to use the eval      My situation  I was pulling some data from an API and writing it to a file locally  Then being able to pull the data from the file and use the Hash   I used IO read   to read the contents of the file into a variable  In this case IO read   creates it as a String   Then used eval   to convert the string into a Hash   read handler   IO read  Path To File json    puts read handler kind of  String    Returns TRUE  a   eval read handler   puts a kind of  Hash    Returns TRUE  puts a  Enter Hash Here     Returns Key   gt  Values  puts a  Enter Hash Here   length   Returns number of key value pairs  puts a  Enter Hash Here    Enter Key Here     Returns associated value   Also just to mention that IO is an ancestor of File  So you can also use File read instead if you wanted

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For different string  you can do it without using dangerous eval method   hash as string       0    gt    answer    gt   1      value    gt   No       1    gt    answer    gt   2      value    gt   Yes       2    gt    answer    gt   3      value    gt   No       3    gt    answer    gt   4      value    gt   1       4    gt    value    gt   2       5    gt    value    gt   3       6    gt    value    gt   4      JSON parse hash as string gsub    gt

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The string created by calling Hash inspect can be turned back into a hash by calling eval on it  However  this requires the same to be true of all of the objects in the hash   If I start with the hash   a   gt  Object new   then its string representation is    a  gt   lt Object 0x7f66b65cf4d0 gt     and I can t use eval to turn it back into a hash because   lt Object 0x7f66b65cf4d0 gt  isn t valid Ruby syntax   However  if all that s in the hash is strings  symbols  numbers  and arrays  it should work  because those have string representations that are  valid Ruby syntax

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I came to this question after writing a one-liner for this purpose  so I share my code in case it helps somebody  Works for a string with only one level depth and possible empty values  but not nil   like       key a   gt   value a    key b   gt   value b    key c   gt          The code is   the string         the hash   Hash new the string 1  -2  split       each   entry  entryMap entry split    gt     value str   entryMap 1   the hash entryMap 0  strip 1  -1  to sym    value str nil         value str strip 1  -2

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I prefer to abuse ActiveSupport  JSON   Their approach is to convert the hash to yaml and then load it   Unfortunately the conversion to yaml isn t simple and you d probably want to borrow it from AS if you don t have AS in your project already   We also have to convert any symbols into regular string-keys as symbols aren t appropriate in JSON   However  its unable to handle hashes that have a date string in them  our date strings end up not being surrounded by strings  which is where the big issue comes in    string      last request at    2011-12-28 23 00 00 UTC    ActiveSupport  JSON decode string gsub     a-zA-z       1   gsub    gt             Would result in an invalid JSON string error when it tries to parse the date value   Would love any suggestions on how to handle this case

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works in rails 4 1 and support symbols without quotes   a     b    just add this to initializers folder   class String   def to hash object     JSON parse self gsub     a-zA-z         1    gsub    gt           symbolize keys   end end

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This short little snippet will do it  but I can t see it working with a nested hash  I think it s pretty cute though  STRING gsub             split       map  h  h1 h2   h split    gt      h1   gt  h2   reduce  merge    Steps 1  I eliminate the         and the     2  I split upon the string wherever it finds a     3  I split each of the substrings that were created with the split  whenever it finds a       Then  I create a hash with the two sides of the hash I just split apart  4  I am left with an array of hashes which I then merge together   EXAMPLE INPUT     user id  11   blog id  2   comment id  1   RESULT OUTPUT    user id    11    blog id    2    comment id    1

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The solutions so far cover some cases but miss some  see below   Here s my attempt at a more thorough  safe  conversion  I know of one corner case which this solution doesn t handle which is single character symbols made up of odd  but allowed characters  For example    gt    gt    lt   is a valid ruby hash   I put this code up on github as well  This code starts with a test string to exercise all the conversions  require  json     Example ruby hash string which exercises all of the permutations of position and type   See http   json org  ruby hash text    alpha   gt   first second  gt  third   gt  first second  gt  third    after comma  gt  foo   gt  symbolvalue   another after comma  gt  foo   gt 10    bravo   gt   symbol  gt  symbolvalue   aftercomma  gt 10   anotheraftercomma  gt  first second  gt  third     charlie   gt  1  gt 10  2  gt  first second  gt  third   3  gt  symbolvalue    delta   gt   first second  gt  third    after comma  gt  foo     echo   gt   symbol   aftercomma    foxtrot   gt  1  2     puts ruby hash text    Transform object string symbols to quoted strings ruby hash text gsub         s       gt  s    s   gt      1  2   gt       Transform object string numbers to quoted strings ruby hash text gsub         s    0-9      0-9    s   gt      1  2   gt       Transform object value symbols to quotes strings ruby hash text gsub         s          0-9      0-9    s   gt  s        s   s       1 2  gt   3       Transform array value symbols to quotes strings ruby hash text gsub          s          s        1  2       Transform object string object value delimiter to colon delimiter ruby hash text gsub         s          0-9      0-9    s   gt      1 2     puts ruby hash text  puts JSON parse ruby hash text    Here are some notes on the other solutions here    Ken Bloom and  Toms Mikoss s solutions use eval which is too scary for me  as Toms rightly points out    zolter s solution works if your hash has no symbols or numeric keys   jackquack s solution works if there are no quoted strings mixed in with the symbols   Eugene s solution works if your symbols don t use all the allowed characters  symbol literals have a broader set of allowed characters    Pablo s solution works as long as you don t have a mix of symbols and quoted strings

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Please consider this solution  Library spec   File  lib ext hash from string rb   require  json   module Ext   module Hash     module ClassMethods         Build a new object from string representation                    from string    name   gt  Joe                      param s  String           return  Hash        def from string s          s gsub      lt        gt nil      null           s gsub      lt        gt                  JSON parse s        end     end   end end  class Hash      nodoc    extend Ext  Hash  ClassMethods end   File  spec lib ext hash from string spec rb   require  ext hash from string   describe  Hash from string  do   it  generally works  do               Basic cases            x   gt  y       x    gt   y               is   gt true      is    gt  true              is   gt false      is    gt  false              is   gt nil      is    gt  nil              a   gt   b   gt  c   ar   1 2        a    gt    b    gt   c    ar    gt   1  2                id   gt 34030   users   gt  14105       id    gt  34030   users    gt   14105              Tricky cases            data   gt     x    gt   y          data    gt      x    gt   y            Value is a  Hash inspect  string which must be preserved        each do  input  expected        output   Hash from string input        expect  input  output   to eq  input  expected      end   end   it end

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I had the same problem  I was storing a hash in Redis  When retrieving that hash  it was a string  I didn t want to call eval str  because of security concerns  My solution was to save the hash as a json string instead of a ruby hash string  If you have the option  using json is easier     redis set key  ruby hash to json    JSON parse redis get key     TL DR  use to json and JSON parse

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I built a gem hash parser that first checks if a hash is safe or not using ruby parser gem  Only then  it applies the eval   You can use it as  require  hash parser     this executes successfully a       key a   gt     key 1a   gt   value 1a    key 2a   gt   value 2a              key b   gt     key 1b   gt   value 1b       p HashParser new safe load a     this throws a HashParser  BadHash exception a       key a   gt  system  ls      p HashParser new safe load a    The tests in https   github com bibstha ruby hash parser blob master test test hash parser rb give you more examples of the things I ve tested to make sure eval is safe

[ruby] How do I convert a String object into a Hash object?

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