blocks|key|1761823|text|keys.inject(hash)+{%7Cacc,+value%7C+acc[value]}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1761824|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>keys.inject(hash) {|acc, value| acc[value]}
</code></pre>

blocks|key|1030083|text|不执行任何错误检查，但是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1030084|h+=+{'k1'+=>+{'s1'+=>+1,+'s2'+=>+2},+'k2'+=>+3}
ks+=+['k1',+'s1']
ks.inject(h){%7Chh,+k%7C+hh[k]}++#+=>+1
['k1',+'s2'].inject(h){%7Chh,+k%7C+hh[k]}+#+=>+2
['k2'].inject(h){%7Chh,+k%7C+hh[k]}+#+=>+3|code-block|syntax|javascript|1030085|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Doesn't do any error checking, but

<pre><code>h = {'k1' =&gt; {'s1' =&gt; 1, 's2' =&gt; 2}, 'k2' =&gt; 3}
ks = ['k1', 's1']
ks.inject(h){|hh, k| hh[k]} # =&gt; 1
['k1', 's2'].inject(h){|hh, k| hh[k]} # =&gt; 2
['k2'].inject(h){|hh, k| hh[k]} # =&gt; 3
</code></pre>

blocks|key|746890|text|最好将对象放在心上，让我们向Hash类添加一个功能|type|unstyled|depth|inlineStyleRanges|entityRanges|data|746891|#+in+intialize+or+whatever
class+Hash
++def+find_path+path+#recursive
++++key+=+path.first
++++if+_path.size+==+1+#+end+of+path+=>+return+value
++++++[key]
++++elsif+[key].kind_of?(Hash)+#+continue
++++++[key].find_path+path[1..-1]
++++else+#+have+to+continue+but+not+a+has+=>+out
++++++nil
++++end
++end

++def+find_path+path+#+not+recursive
++++_path+=+path.clone+#copy+to+shift
++++_tree+=+self+#start+with+self
++++while(_path.size+>+1+&&+_tree)+do+#while+not+the+end+and+_tree+
++++++_v+=+_tree[_path.shift]
++++++_tree+=+_v.kind_of?(Hash)+?+_v+:+nil
++++end
++++_tree+?+_tree[_path.first]+:+nil
++end
end|code-block|syntax|javascript|746892|这样：|746893|hash+=+{:v1+=>+{:v1.1+=>+"yes",+:v1.2+=>+"false"}}
hash.find_path+[:v1,+:v1.1]
#+=>+"yes"
hash.find_path+[:v1]
#+=>+{:v1.1+=>+"yes",+:v1.2+=>+"false"}
hash.find_path+[:v2]
#+=>+nil
hash.find_path+[:v1,+:v1.3]
#+=>+nil|746894|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Better keep object in mind so let's add a feature to Hash class

<pre><code># in intialize or whatever
class Hash
 def find_path path #recursive
 key = path.first
 if _path.size == 1 # end of path =&gt; return value
 [key]
 elsif [key].kind_of?(Hash) # continue
 [key].find_path path[1..-1]
 else # have to continue but not a has =&gt; out
 nil
 end
 end

 def find_path path # not recursive
 _path = path.clone #copy to shift
 _tree = self #start with self
 while(_path.size &gt; 1 &amp;&amp; _tree) do #while not the end and _tree 
 _v = _tree[_path.shift]
 _tree = _v.kind_of?(Hash) ? _v : nil
 end
 _tree ? _tree[_path.first] : nil
 end
end
</code></pre>

This way :

<pre><code>hash = {:v1 =&gt; {:v1.1 =&gt; "yes", :v1.2 =&gt; "false"}}
hash.find_path [:v1, :v1.1]
# =&gt; "yes"
hash.find_path [:v1]
# =&gt; {:v1.1 =&gt; "yes", :v1.2 =&gt; "false"}
hash.find_path [:v2]
# =&gt; nil
hash.find_path [:v1, :v1.3]
# =&gt; nil
</code></pre>

blocks|key|5068318|text|这是我的解决方案(它类似于proxygear的，但它不会对Hash进行猴子补丁，并且在没有参数的情况下调用时它的行为是正确的)。我认为这比两个基于注入的解决方案更好，因为如果你试图访问DNE的路径，它们将会爆炸。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5068319|class+TraversibleHash
++attr_accessor+:hash

++def+initialize(hash)
++++self.hash+=+hash
++end

++def+access(*keys)
++++recursive_access+keys,+hash
++end

private

++def+recursive_access(keys,+hash)
++++return+nil+if+keys.empty?
++++element+=+hash.fetch(keys.shift)+{+return+nil+}
++++return+element+if+keys.empty?
++++return+nil+unless+element.kind_of?+Hash+#+<--+should+maybe+raise+an+error?
++++recursive_access+keys,+element
++end
end|code-block|syntax|javascript|5068320|下面是测试套件：|5068321|describe+TraversibleHash+do
++let(:traversible)+{+TraversibleHash.new+'key1'+=>+{+'sub1'+=>+1,+'sub2'+=>+2+},+'key2'+=>+3,+nil+=>+1+}

++it+'returns+nil+when+invoked+without+args'+do
++++traversible.access.should+be_nil
++end

++it+'returns+nil+when+accessing+nonexistent+keys'+do
++++traversible.access('key3').should+be_nil
++++traversible.access('key2',+'key3').should+be_nil
++++traversible.access('key1',+'sub3').should+be_nil
++++traversible.access('key1',+'sub2',+'subsub1').should+be_nil
++++traversible.access('abc',+'def',+'ghi').should+be_nil
++end

++it+'finds+toplevel+keys'+do
++++traversible.access('key2').should+==+3
++++traversible.access('key1').should+==+{'sub1'+=>+1,+'sub2'+=>+2}
++end

++it+'traverses+nested+hashes+to+find+nested+keys'+do
++++traversible.access('key1',+'sub1').should+==+1
++++traversible.access('key1',+'sub2').should+==+2
++++TraversibleHash.new(1=>{2=>{3=>4}}).access(1,+2,+3).should+==+4
++end
end|5068322|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Here is my solution (it is similar to proxygear's, but it does not monkey patch Hash, and it behaves correctly when invoked with no args). I think it is better than the two inject based solutions because they will blow up if you try to access paths that DNE. 

<pre><code>class TraversibleHash
 attr_accessor :hash

 def initialize(hash)
 self.hash = hash
 end

 def access(*keys)
 recursive_access keys, hash
 end

private

 def recursive_access(keys, hash)
 return nil if keys.empty?
 element = hash.fetch(keys.shift) { return nil }
 return element if keys.empty?
 return nil unless element.kind_of? Hash # &lt;-- should maybe raise an error?
 recursive_access keys, element
 end
end
</code></pre>

Here is the test suite:

<pre><code>describe TraversibleHash do
 let(:traversible) { TraversibleHash.new 'key1' =&gt; { 'sub1' =&gt; 1, 'sub2' =&gt; 2 }, 'key2' =&gt; 3, nil =&gt; 1 }

 it 'returns nil when invoked without args' do
 traversible.access.should be_nil
 end

 it 'returns nil when accessing nonexistent keys' do
 traversible.access('key3').should be_nil
 traversible.access('key2', 'key3').should be_nil
 traversible.access('key1', 'sub3').should be_nil
 traversible.access('key1', 'sub2', 'subsub1').should be_nil
 traversible.access('abc', 'def', 'ghi').should be_nil
 end

 it 'finds toplevel keys' do
 traversible.access('key2').should == 3
 traversible.access('key1').should == {'sub1' =&gt; 1, 'sub2' =&gt; 2}
 end

 it 'traverses nested hashes to find nested keys' do
 traversible.access('key1', 'sub1').should == 1
 traversible.access('key1', 'sub2').should == 2
 TraversibleHash.new(1=&gt;{2=&gt;{3=&gt;4}}).access(1, 2, 3).should == 4
 end
end
</code></pre>

blocks|key|1030147|text|从Ruby2.3.0开始，你可以使用Hash#dig，它可以做到这一点：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1030148|hash.dig(*keys)|code-block|syntax|javascript|1030149|在迁移之前，您可以使用+gem。|1030150|entityMap^0|I|8|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

From Ruby 2.3.0 onward, you can use <code>Hash#dig</code>, which does exactly that:

<pre><code>hash.dig(*keys)
</code></pre>

You can use the <a href="https://github.com/Invoca/ruby_dig" rel="nofollow">ruby_dig</a> gem until you migrate.

I have Hash like this, representing a data tree

<pre><code>hash = {
 'key1' =&gt; {
 'sub1' =&gt; 1,
 'sub2' =&gt; 2
 },
 'key2' =&gt; 3
}
</code></pre>

I want to explore the tree with an array of keys representing a path.
Some exemples :

with a simple path:

<pre><code>keys = ['key2']
</code></pre>

I want to get <code>3</code>

with this path:

<pre><code>keys = ['key1', 'sub1']
</code></pre>

I want to get <code>1</code>

with invalide path :

<pre><code>keys = ['key1', 'sub1', 'blabla']
keys = ['key1', 'blabla']
</code></pre>

get <code>nil</code>

etc ... etc ... you get the idea

get ruby hash value by keys

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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