2-Patch-Hash

FMI

How can I follow those FMI problems, heh? Watashi wa besuto o tsukushimasu!

Resources

Enumerable is a gem. Go through its documentation. Hash builds on top of it.

• http://www.ruby-doc.org/core-2.1.3/Enumerable.html
• http://www.ruby-doc.org/core-2.1.3/Hash.html

Use whatever you need in order to solve the following problems:

Hash#pick

Hash#pick returns a new hash, with only the specified keys in it.

class Hash
  def pick(*keys)
    # Your code goes here.
  end
end

>> {a: 1, b: 2, c: 3}.pick(:a, :b)
=> {:a=>1, :b=>2}

Hash#except

Hash#except returns a new hash, without the specified keys in it. Kind of like a reversed Hash#pluck.

class Hash
  def except(*keys)
    # Your code goes here.
  end
end

>> {a: 1, b: 2, d: nil}.except(:d)
=> {:a=>1, :b=>2}

Hash#compact_values

Hash#compact_values returns a new hash, with only the truthy keys in it.

class Hash
  def compact_values
    # Your code goes here.
  end
end

>> {a: 1, b: 2, c: false, d: nil}.compact_values
=> {:a=>1, :b=>2}

Hash#defaults

Hash#defaults returns a new hash, setting values only if they were not already present in the hash.

class Hash
  def defaults(hash)
    # Your code goes here.
  end
end

>> {a: 1, b: 2}.defaults(a: 4, c: 3)
=> {:a=>1, :b=>2, :c=>3}

Bang Bang

Add bang version methods (e.g. Hash#pick!) that change the hash inplace. Think whether you can reuse the implementations with the non-bang version methods.