How to change Hash values

Question

I d like to replace each value in a hash with value some method   For example  for given a simple hash     a    gt   b    c    gt   d       every value should be  upcased  so it looks like     a    gt   B    c    gt   D     I tried  collect and  map but always just get arrays back  Is there an elegant way to do this   UPDATE   Damn  I forgot  The hash is in an instance variable which should not be changed  I need a new hash with the changed values  but would prefer not to define that variable explicitly and then loop over the hash filling it  Something like   new hash   hash magic

User · Answer

Try this function   h     a    gt   b    c    gt   d   h each  i j  j upcase     now contains   a    gt   B    c    gt   D

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There s a method for that in ActiveSupport v4 2 0  It s called transform values and basically just executes a block for each key-value-pair   Since they re doing it with a each I think there s no better way than to loop through   hash    sample   gach    result      hash each do  key  value    result key    do stuff value  end   Update   Since Ruby 2 4 0 you can natively use  transform values and  transform values

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my hash each    k  v  my hash k    v upcase      or  if you d prefer to do it non-destructively  and return a new hash instead of modifying my hash   a new hash   my hash inject        h   k  v   h k    v upcase  h      This last version has the added benefit that you could transform the keys too

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Rails-specific  In case someone only needs to call to s method to each of the values and is not using Rails 4 2   which includes transform values method link   you can do the following     original hash      a   gt   a    b   gt  BigDecimal  23 4        gt    a  gt  a    b  gt   lt BigDecimal 5c03a00  0 234E2  18 18  gt   JSON original hash to json     gt    a   gt  a    b   gt  23 4     Note  The use of  json  library is required   Note 2  This will turn keys into strings as well

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I do something like this      new hash   Hash  original hash collect  key value   key value   1   flatten    This provides you with the facilities to transform the key or value via any expression also  and it s non-destructive  of course

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If you know that the values are strings  you can call the replace method on them while in the cycle  this way you will change the value   Altohugh this is limited to the case in which the values are strings and hence doesn t answer the question fully  I thought it can be useful to someone

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You can collect the values  and convert it from Array to Hash again   Like this   config   Hash  config collect   k v   k  v upcase

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new hash   old hash merge old hash  do   key  value   value               value upcase            end    old hash     a    gt   b    c    gt   d     new hash     a    gt   B    c    gt   D

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This will do it   my hash each with object         key  value   hash  hash key    value upcase     As opposed to inject the advantage is that you are in no need to return the hash again inside the block

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Ruby has the tap method  1 8 7  1 9 3 and 2 1 0  that s very useful for stuff like this   original hash      a   gt   a    b   gt   b    original hash clone tap   h  h each   k v  h k    v upcase         gt    a  gt  A    b  gt  B   original hash     gt    a  gt  a    b  gt  b

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Since ruby 2 4 0 you can use native Hash transform values method   hash     a    gt   b    c    gt   d   new hash   hash transform values  amp  upcase      gt    a    gt   B    c    gt   D     There is also destructive Hash transform values  version

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You may want to go a step further and do this on a nested hash  Certainly this happens a fair amount with Rails projects    Here s some code to ensure a params hash is in UTF-8     def convert hash hash     hash inject     do  h  k v         if v kind of  String         h k    to utf8 v         else         h k    convert hash v        end       h     end         end          Iconv UTF-8 helper     Converts strings into valid UTF-8          param  String  untrusted string the string to convert to UTF-8      return  String  your string in UTF-8   def to utf8 untrusted string        ic   Iconv new  UTF-8  IGNORE    UTF-8       ic iconv untrusted string        0  -2    end

[ruby] How to change Hash values?

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