method

slice

Importance_2
Ruby on Rails latest stable (v6.1.7.7) - 2 notes - Class: Hash

Method deprecated or moved

This method is deprecated or moved on the latest stable version. The last existing version (v5.2.3) is shown here.

These similar methods exist in v6.1.7.7:

slice(*keys) public

Slices a hash to include only the given keys. Returns a hash containing the given keys.

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

This is useful for limiting an options hash to valid keys before passing to a method:

def search(criteria = {})
  criteria.assert_valid_keys(:mass, :velocity, :time)
end

search(options.slice(:mass, :velocity, :time))

If you have an array of keys you want to limit to, you should splat them:

valid_keys = [:mass, :velocity, :time]
search(options.slice(*valid_keys))
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August 20, 2013
2 thanks

everything is ok

Olefine, I’m not sure here is a good place for such questions (better use stackoverflow for example), but answer for your question is that Rails provide slice (and many other methods) not only for Hash class but for HashWithIndifferentAccess too such as for any other superclass of Hash, so they use

hash = self.class.new

for a reason. {} is a literal only for Hash.

August 12, 2013
0 thanks

unuseful code

Why it use?

hash = self.class.new

Instead it, we may use

hash = {}