How to find a hash key containing a matching value

Question

Given I have the below clients hash  is there a quick ruby way  without having to write a multi-line script  to obtain the key given I want to match the client id  E g  How to get the key for client id     2180    clients        yellow   gt   client id   gt  2178        orange   gt   client id   gt  2180        red   gt   client id   gt  2179        blue   gt   client id   gt  2181

User · Answer

You could use hashname key valuename   Or  an inversion may be in order  new hash   hashname invert will give you a new hash that lets you do things more traditionally

User · Answer

From the docs     Object   detect ifnone   nil    obj         Object   find ifnone   nil    obj         Object  detect ifnone   nil   Object  find ifnone   nil    Passes each entry in enum to block  Returns the first for which block is not false  If no object matches  calls ifnone and returns its result when it is specified  or returns nil otherwise   If no block is given  an enumerator is returned instead    1  10  detect    i  i   5    0 and i   7    0        gt  nil  1  100  detect   i  i   5    0 and i   7    0        gt  35   This worked for me   clients detect  client  client last  client id       2180       gt    orange     client id   gt  2180      clients detect  client  client last  client id       999999       gt  nil    See  http   rubydoc info stdlib core 1 9 2 Enumerable find-instance method

User · Answer

You can invert the hash  clients invert  client id   gt  2180   returns  orange

User · Answer

Another approach I would try is by using  map  clients map   key     key if clients key       client id   gt  2180     compact     gt    orange     This will return all occurences of given value  The underscore means that we don t need key s value to be carried around so that way it s not being assigned to a variable  The array will contain nils if the values doesn t match - that s why I put  compact at the end

User · Answer

The best way to find the key for a particular value is to use key method that is available for a hash      gender     MALE    gt  1   FEMALE    gt  2  gender key 1     gt  MALE   I hope it solves your problem

User · Answer

Ruby 1 9 and greater   hash key value    gt  key   Ruby 1 8   You could use hash index     hsh index value    gt  key        Returns the key for a given value  If   not found  returns nil         h      a    gt  100   b    gt  200     h index 200       gt   b    h index 999       gt  nil   So to get  orange   you could just use   clients key   client id    gt   2180

User · Answer

According to ruby doc http   www ruby-doc org core-1 9 3 Hash html method-i-key key value  is the method to find the key on the base of value   ROLE     customer    gt  1   designer    gt  2   admin    gt  100  ROLE key 2    it will return the  designer

User · Answer

You could use Enumerable select   clients select  key  hash  hash  client id       2180       gt     orange     client id   gt  2180       Note that the result will be an array of all the matching values  where each is an array of the key and value

User · Answer

try this   clients find  key value  value  client id       2178   first

User · Answer

Heres an easy way to do find the keys of a given value       clients            yellow   gt   client id   gt  2178            orange   gt   client id   gt  2180            red   gt   client id   gt  2179            blue   gt   client id   gt  2181              p clients rassoc  client id   gt  2180        and to find the value of a given key       p clients assoc  orange      it will give you the key-value pair

[ruby] How to find a hash key containing a matching value

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