Append key value pair to hash with in Ruby

Question

In Ruby  one can append values to existing arrays using  lt  lt    a      a  lt  lt   foo    but  can you also append key value pairs to an existing hash   h      h  lt  lt   key  bar    I know you can do   h  key       h  key   lt  lt   bar    but that s not I want   Thanks

User · Answer

No  I don t think you can append key value pairs  The only thing closest that I am aware of is using the store method   h      h store  key    value

User · Answer

Similar as they are  merge  and store treat existing hashes differently depending on keynames  and will therefore affect your preference  Other than that from a syntax standpoint  merge  s key   value  syntax closely matches up against JavaScript and Python  I ve always hated comma-separating key-value pairs  personally   hash      hash merge  key   value   hash merge   key   gt   value   puts hash        key  gt  value     hash      hash store  key   value   hash store  key    value   puts hash        key  gt  value    key   gt  value     To get the shovel operator  lt  lt  working  I would advise using Mark Thomas s answer

User · Answer

There is merge    h      h merge  key   bar       gt    key  gt  bar

User · Answer

Since hashes aren t inherently ordered  there isn t a notion of appending  Ruby hashes since 1 9 maintain insertion order  however  Here are the ways to add new key value pairs   The simplest solution is   h  key     bar    If you want a method  use store   h store  key   bar     If you really  really want to use a  shovel  operator   lt  lt    it is actually appending to the value of the hash as an array  and you must specify the key   h  key   lt  lt   bar    The above only works when the key exists  To append a new key  you have to initialize the hash with a default value  which you can do like this   h   Hash new   h  k  h k        h  key   lt  lt   bar    You may be tempted to monkey patch Hash to include a shovel operator that works in the way you ve written   class Hash   def  lt  lt  k v      self store k v    end end   However  this doesn t inherit the  syntactic sugar  applied to the shovel operator in other contexts   h  lt  lt   key   bar   doesn t work h  lt  lt   key   bar   works

User · Answer

Perhaps you want Hash merge    1 9 3p194  015  gt  h       gt      1 9 3p194  016  gt  h merge  key   gt   bar      gt    key  gt  bar    1 9 3p194  017  gt     If you want to change the array in place use merge   1 9 3p194  016  gt  h merge   key   gt   bar      gt    key  gt  bar

User · Answer

I had to do a similar thing but I needed to add values with same keys  When I use merge or update I can t push values with same keys  So I had to use array of hashes         my hash static     header   gt   company   gt   xx    usercode   gt   xx    password   gt   xx                          type  gt   n n    msgheader   gt  from    body  gt         my hash dynamic     mp  gt   msg  gt message   no  gt phones                my hash full   my hash static  body  push my hash dynamic

[ruby] Append key/value pair to hash with << in Ruby

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