How to replace a hash key with another key

Question

I have a condition where  I get a hash     hash      id   gt  4de7140772f8be03da000018            and I want this hash as    hash     id   gt  4de7140772f8be03da000018             P S  I don t know what are the keys in the hash  they are random which comes      with an     prefix for every key and I want no underscores

User · Answer

you can do   hash inject      option   k v    option  id     v if k      id   option    This should work for your case

User · Answer

hash each   k v  hash delete k   amp  amp  hash k 1  -1   v if k 0 1

User · Answer

h inject        m   k v   m k sub             v  m

User · Answer

I went overkill and came up with the following  My motivation behind this was to append to hash keys to avoid scope conflicts when merging together flattening hashes   Examples  Extend Hash Class  Adds rekey method to Hash instances     Adds additional methods to Hash class   Hash     Changes the keys on a hash     Takes a block that passes the current key     Whatever the block returns becomes the new key     If a hash is returned for the key it will merge the current hash      with the returned hash from the block  This allows for nested rekeying    def rekey     self each with object     do   key  value   previous        new key   yield key  value        if new key is a  Hash          previous merge  new key        else         previous new key    value       end     end   end end   Prepend Example  my feelings about icecreams       vanilla   Delicious     chocolate   Too Chocolatey     strawberry   It Is Alright        my feelings about icecreams rekey    key     key  icecream  to sym       gt    vanilla icecream  gt  Delicious    chocolate icecream  gt  Too Chocolatey    strawberry icecream  gt  It Is Alright        Trim Example     id  1     something    what      rekey do  key    trimmed   key to s tr            trimmed to sym end     gt    id  gt 1   something  gt  what       Flattening and Appending a  Scope   If you pass a hash back to rekey it will merge the hash which allows you to flatten collections  This allows us to add scope to our keys when flattening a hash to avoid overwriting a key upon merging   people       bob        name   Bob       toys            what   car   color   red             what   ball   color   blue                 tom        name   Tom       toys            what   house   color   blue  da ba dee da ba die             what   nerf gun   color   metallic                 people rekey do  person  person info    person info rekey do  key         person    key   to sym   end end      gt           bob name  gt  Bob        bob toys  gt           what  gt  car    color  gt  red            what  gt  ball    color  gt  blue               tom name  gt  Tom        tom toys  gt           what  gt  house    color  gt  blue  da ba dee da ba die            what  gt  nerf gun    color  gt  metallic

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For Ruby 2 5 or newer with transform keys and delete prefix   delete suffix methods  hash1       id    gt   random1    hash2      old first    gt   123456    old second    gt   234567    hash3      first com    gt   google com    second com    gt   amazon com     hash1 transform keys    key  key delete prefix            gt    quot id quot   gt  quot random1 quot   hash2 transform keys    key  key delete prefix  old          gt    quot first quot   gt  quot 123456 quot    quot second quot   gt  quot 234567 quot   hash3 transform keys    key  key delete suffix   com         gt    quot first quot   gt  quot google com quot    quot second quot   gt  quot amazon com quot

User · Answer

hash  new key    hash delete  old key

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rails Hash has standard method for it   hash transform keys   key  key to s upcase     http   api rubyonrails org classes Hash html method-i-transform keys  UPD  ruby 2 5 method

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If we want to rename a specific key in hash then we can do it as follows  Suppose my hash is  my hash     test      ruby hash demo    Now I want to replace  test  by  message   then    my hash  message     my hash delete  test

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Answering exactly what was asked  hash     quot  id quot   gt  quot 4de7140772f8be03da000018 quot   hash transform keys    key  key 1          gt    quot id quot   gt  quot 4de7140772f8be03da000018 quot    The method transform keys exists in the Hash class since Ruby version 2 5  https   blog bigbinary com 2018 01 09 ruby-2-5-adds-hash-transform keys-method html

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Previous answers are good enough  but they might update original data  In case if you don t want the original data to be affected  you can try my code    newhash hash reject  k  k    id   merge  id hash   id       First it will ignore the key   id  then merge with the updated one

User · Answer

If all the keys are strings and all of them have the underscore prefix  then you can patch up the hash in place with this   h keys each    k  h k 1  k length - 1     h k   h delete k      The k 1  k length - 1  bit grabs all of k except the first character  If you want a copy  then   new h   Hash h map    k  v   k 1  k length - 1   v       Or  new h   h inject         x   k v   x k 1  k length - 1     v  x     You could also use sub if you don t like the k   notation for extracting a substring   h keys each    k  h k sub   A           h k   h delete k    Hash h map    k  v   k sub   A         v     h inject         x   k v   x k sub   A           v  x     And  if only some of the keys have the underscore prefix   h keys each do  k    if k 0 1              h k 1  k length - 1     h k      h delete k    end end   Similar modifications can be done to all the other variants above but these two   Hash h map    k  v   k sub   A         v     h inject         x   k v   x k sub   A           v  x     should be okay with keys that don t have underscore prefixes without extra modifications

[ruby-on-rails] How to replace a hash key with another key

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