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I would like to know how to return a specific key from a Hash?
Example:
moves = Hash["Kick", 100, "Punch", 50]
How would I return the first key "Kick" from this Hash?
NOTE: I'm aware that the following function will return all keys from the hash but I'm just interested in returning one key.
moves.keys #=> ["Kick", "Punch"]
855
hash.fetch(key) { | key | block } Returns a value from hash for the given key. If the key can't be found, and there are no other arguments, it raises an IndexError exception; if default is given, it is returned; if the optional block is specified, its result is returned.
new : This method returns a empty hash. In the first form the access return nil. If obj is specified then, this object is used for all default values. If a block is specified, then it will be called by the hash key and objects and return the default value.
To find a hash key by it's value, i.e. reverse lookup, one can use Hash#key . It's available in Ruby 1.9+.
You can use:
first_key, first_value = moves.first
Or equivalently:
first_key = moves.first.first
Quite nice too:
first_key = moves.each_key.first
The other possibility, moves.keys.first will build an intermediary array for all keys which could potentially be very big.
Note that Ruby 1.8 makes no guarantee on the order of a hash, so the key you will get not always be the same. In Ruby 1.9, you will always get the same key ("Kick" in your example).
67
moves.keys[0]
will give you the first key. You can get all keys by changing the argument passed (0, 1,...etc)
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