ruby数组和Hash直接的转换

Ruby Hash to array of values

Also, a bit simpler....

>> hash = { "a"=>["a", "b", "c"], "b"=>["b", "c"] }
=> {"a"=>["a", "b", "c"], "b"=>["b", "c"]}
>> hash.values
=> [["a", "b", "c"], ["b", "c"]]
Ruby doc here


Get a value from an array of hashes in ruby

The select statement will return all the hashes with the key 13.

If you already know which hash has the key then the below code will give u the answer.

ary[1][13]
However if you are not sure which of your hashes in the array has the value, then you could do the following:

values = ary.map{|h| h[13]}.compact
Values will have the value of key 13 from all the hashes which has the key 13.


Ruby convert an Array to Hash values with specific keys

You can use #zip

your_array = ["12", "21", "1985"]
keys = ['month', 'day', 'year']
keys.zip(your_array).to_h

Convert hash to array of hashes

Leveraging Array#transpose and Array#to_h

keys = list.keys
list.values.transpose.map { |v| keys.zip(v).to_h }

Collect specific values from an array of hashes

A Hash is a dictionary-like collection of unique keys and their values. Also called associative arrays, they are similar to Arrays, but where an Array uses integers as its index, a Hash allows you to use any object type.

Of course, a value can be any object - string, method, nil, number, object. So, only after create, we can know that is saved in our hash. For this reason when trying to get all key:

data.keys # => ["etag", "items"]
There is no any nested key. So finding value by missing key return nil.

To select all videoId you must do something like this:

data["items"].map { |item| item["snippet"]["resourceId"]["videoId"] }.compact
Also, you can update Hash class as there:

class Hash
  def deep_find(key, object=self, found=nil)
    if object.respond_to?(:key?) && object.key?(key)
      return object[key]
    elsif object.is_a? Enumerable
      object.find { |*a| found = deep_find(key, a.last) }
      return found
    end
  end
end
And then run

data["items"].map { |item| item.deep_find('videoId') }
That method avoids the error when the json will have a variable structure.


Convert array of hashes to array

a=[{:code=>"404"}, {:code=>"302"}, {:code=>"200"}] 
puts a.map{|x|x.values}.flatten.inspect
output

["404", "302", "200"]

ruby: how to convert hash into array

try this:

{0=>0.07394653730860076, 1=>0.0739598476853163, 2=>0.07398647083461522}.to_a
#=> [[0, 0.07394653730860076], [1, 0.0739598476853163], [2, 0.07398647083461522]]

Creating a Hash with values as arrays and default value as empty array

Lakshmi is right. When you created the Hash using Hash.new([]), you created one array object.

Hence, the same array is returned for every missing key in the Hash.

That is why, if the shared array is edited, the change is reflected across all the missing keys.

Using:

Hash.new { |h, k| h[k] = [] }
Creates and assigns a new array for each missing key in the Hash, so that it is a unique object.

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