如何从 Ruby 中的哈希表中获取第一个键值对
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How to get the first key and value pair from a hash table in Ruby
提问by Xitcod13
I'm trying to get the first key and value key from a hash table in ruby. I don't know the key values of the hash because it is passed to the method. I cant find anywhere online how to find the first key/value as a separate hash table.
I think hash[0]will just try to find an element with a name 0 it just returns nilwhen I run the code.
我正在尝试从 ruby 中的哈希表中获取第一个键和值键。我不知道散列的键值，因为它被传递给方法。我在网上找不到任何地方如何找到第一个键/值作为单独的哈希表。我认为hash[0]只会尝试查找名称为 0 的元素，它会nil在我运行代码时返回。
I know I can find the key name and the value and then create a new hash from them but i wonder if there is an easier way to do this so I get a hash right away.
我知道我可以找到键名和值，然后从它们创建一个新的散列，但我想知道是否有更简单的方法来做到这一点，所以我马上得到一个散列。
here is my code:
这是我的代码：
def rps_game_winner(game)
rock_in_hash = game.invert['R']
paper_in_hash = game.invert['P']
scissors_in_hash = game.invert['S']
if(rock_in_hash)
if(paper_in_hash)
return paper_in_hash;
elsif(scissors_in_hash)
return rock_in_hash
end
elsif(paper_in_hash)
if(rock_in_hash)
return paper_in_hash
elsif(scissors_in_hash)
return scissors_in_hash
end
end
key = game.keys[-1]
value = game.values[-1]
winner = {key => value}
return winner
end
game_one = { "Bob" => 'P', "Jim" => 'P' }
puts rps_game_winner(game_one)
This gets me the correct result the problem is I don't understand why it's -1 instead of zero... And i was hoping there was a better way to get the first key/value pair of a hash table instead of creating new hash table with the key and value you retrieved from the previous table.
这让我得到了正确的结果问题是我不明白为什么它是 -1 而不是零......而且我希望有更好的方法来获取哈希表的第一个键/值对而不是创建新的哈希包含您从上一个表中检索到的键和值的表。
回答by pguardiario
You can just do
你可以做
key, value = hash.first
or if you prefer:
或者，如果您更喜欢：
key = hash.keys[0]
value = hash.values[0]
Then maybe:
那么也许：
new_hash = {key => value}
回答by metakungfu
There is a shorter answerthat does not require you to use extra variables:
有一个较短的答案，不需要您使用额外的变量：
h = { "a" => 100, "b" => 200 , "c" => 300, "d" => 400, "e" => 500}
Hash[*h.first] #=> {"a" => 100}
Or if you want to retrieve a key/value at a any single position
或者，如果您想在任何单个位置检索键/值
Hash[*h.to_a.at(1)] #=> {"b" => 200}
Or retrieve a key/values from a range of positions:
或者从一系列位置检索键/值：
Hash[h.to_a[1,3]] #=> {"b"=>200, "c"=>300, "d"=>400}
