Ruby value of a hash key

Question

I ve got a list of values that are in a Ruby hash   Is there a way to check the value of the key and if it equals  X   then do  Y    I can test to see if the hash has a key using hash has key   but now I need to know if hash key     X  then

User · Answer

This question seems to be ambiguous   I ll try with my interpretation of the request   def do something data     puts  Found    data   end  a      x    gt   test    y    gt   foo    z    gt   bar    a each    key value  do something value  if key     x      This will loop over all the key value pairs and do something only if the key is  x

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As an addition to e g   Intrepidd s answer  in certain situations you want to use fetch instead of     For fetch not to throw an exception when the key is not found  pass it a default value   puts  ok  if hash fetch  key   nil      X    Reference  https   docs ruby-lang org en 2 3 0 Hash html

User · Answer

It seems that your question is maybe a bit ambiguous   If    values    in the first sentence means any generic value  i e  object  since everything in Ruby can be viewed as an object   then one of the other answers probably tells you what you need to know  i e  use Hash     e g  hash some key   to find the value associated with a key    If  however     values    in first sentence is taken to mean the value part of the    key  value pairs     as are stored in hashes   then your question seems like it might be about working in the other direction  key for a given value    You can find a key that leads to a certain value with  Hash key   ruby-1 9 2-head  001  gt  hash      a   gt   1    b   gt   two   c   gt  3   bee    gt   two      gt    a  gt  1    b  gt  two   c  gt 3   bee   gt  two   ruby-1 9 2-head  002  gt  a value    two    gt   two  ruby-1 9 2-head  003  gt  hash key a value     gt   b    If you are using a Ruby earlier than 1 9  you can use Hash index   When there are multiple keys with the desired value  the method will only return one of them  If you want all the keys with a given value  you may have to iterate a bit   ruby-1 9 2-head  004  gt  hash  b     hash  bee      gt  true  ruby-1 9 2-head  005  gt  keys   hash inject     do   all keys with value a value ruby-1 9 2-head  006  gt         l kv  kv 1     a value   l  lt  lt  kv 0    l ruby-1 9 2-head  007  gt    end    gt    b   bee      Once you have a key  the keys  that lead to the value  you can compare them and act on them with if unless case expressions  custom methods that take blocks  et cetera  Just how you compare them depends on the kind of objects you are using for keys  people often use strings and symbols  but Ruby hashes can use any kind of object as keys  as long as they are not modified while they serve as keys

User · Answer

How about this   puts  ok  if hash variable  key       X    You can access hash values with the    operator

User · Answer

I didn t understand your problem clearly but I think this is what you re looking for Based on my understanding     person       name   gt  BillGates    company name   gt  Microsoft    position   gt  Chairman      person delete if   key  value  key     name    doing something if the key     something     Output    company name   gt  Microsoft    position   gt  Chairman

User · Answer

Hashes are indexed using the square brackets       Just as arrays  But instead of indexing with the numerical index  hashes are indexed using either the string literal you used for the key  or the symbol  So if your hash is similar to   hash      key1    gt   value1    key2    gt   value2      you can access the value with   hash  key1     or for  hash      key1   gt   value1    key2   gt   value2     or the new format supported in Ruby 1 9  hash     key1   value1   key2   value2      you can access the value with   hash  key1

[ruby] Ruby value of a hash key?

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