what about
Hash[nested_hash.map {|k,v| [k,(v.respond_to?(:except)?v.except("nested_key2"):v)] }]
=> {"key1"=>"value1", "key2"=>{"nested_key1"=>"nestedvalue1"}}
ugh.
سؤال
I am now trying for some hours to remove a nested hash key of a hash list. I saw many solution non-nested hashs wich looks like this:
sample_hash = {"key1" => "value1", "key2" => "value2"}
sample_hash.except("key1")
This results in:
{"key2"=>"value2"}
But if I try to use the except method on a hash with nested key then it doesn't work. Here my code:
nested_hash = {"key1"=>"value1", "key2"=>{
"nested_key1"=>"nestedvalue1",
"nested_key2"=>"nestedvalue2"
}
}
nested_hash.except("nested_key2")
The except() method returns the nested_hash without any changes. I have looked for a solution how I can pass nested hash-keys to the except method, but couldn't find anything. Is it even possible to pass nested keys to this method or should I use some other method which deletes a nested hash key from my hash list?
المحلول
what about
Hash[nested_hash.map {|k,v| [k,(v.respond_to?(:except)?v.except("nested_key2"):v)] }]
=> {"key1"=>"value1", "key2"=>{"nested_key1"=>"nestedvalue1"}}
ugh.
نصائح أخرى
The accepted solution is valid for the scenario given but if you're looking for something that will do this for arbitrarily nested hash tables then you're going to need a recursive solution. I couldn't find a suitable solution anywhere, so I wrote one here.
Reproduced here with annotations:
class Hash
def except_nested(key)
r = Marshal.load(Marshal.dump(self)) # deep copy the hashtable
r.except_nested!(key)
end
def except_nested!(key)
self.except!(key)
self.each do |_, v| # essentially dfs traversal calling except!
v.except_nested!(key) if v.is_a?(Hash)
end
end
end
adding it to the Hash
class so that you can call it the same way you call except/except! anywhere else.
t = { a: '1', b: { c: '3', d: '4' } }
r = t.except_nested(:c)
# r => {:a=>"1", :b=>{:d=>"4"}}
# t => {:a=>"1", :b=>{:c=>"3", :d=>"4"}}
t.except_nested!(:c)
# t => {:a=>"1", :b=>{:d=>"4"}}
try
my_hash = Hash[nested_hash.map {|k,v| {k=>v.is_a? Array ? v.except("nested_key2") : v}}.map {|key, value| [key, value]}]
But this seems wrong, I wish I never started down this path, I'm willing to bet there is an easier way!