ruby using the “&:methodname” shortcut from array.map(&:methodname) for hash key strings rather than methodname

by

You can do this with a lambda:

extract_keyname = ->(h) { h[:keyname] }
ary_of_hashes.map(&extract_keyname)

This tends to be more useful if the block’s logic is more complicated than simply extracting a value from a Hash. Also, attaching names to your bits of logic can help clarify what a chain of Enumerable method calls is trying to do.

You can also have a lambda which returns a lambda if you’re doing this multiple times:

extract = ->(k) { ->(h) { h[k] } }
ary_of_hashes.map(&extract[:keyname])
ary_of_hashes.map(&extract[:other_key])

or a lambda building method:

def extract(k)
  ->(h) { h[k] }
end

ary_of_hashes.map(&extract(:keyname))
ary_of_hashes.map(&extract(:other_key))

More Related Contents:

  1. How to remove empty string in hash
  2. Strange, unexpected behavior (disappearing/changing values) when using Hash default value, e.g. Hash.new([])
  3. Is there any difference between the `:key => “value”` and `key: “value”` hash notations?
  4. Converting a nested hash into a flat hash
  5. Is Hash Rocket deprecated?
  6. Ruby Style: How to check whether a nested hash element exists
  7. what’s different between each and collect method in Ruby [duplicate]
  8. Group hashes by keys and sum the values
  9. Difference between map and collect in Ruby?
  10. How do I search within an array of hashes by hash values in ruby?
  11. Ruby Hash with duplicate keys?
  12. Performance of Arrays and Hashes in Ruby
  13. Comparing ruby hashes [duplicate]
  14. Find key/value pairs deep inside a hash containing an arbitrary number of nested hashes and arrays
  15. Ruby method Array#
  16. How to get a specific output iterating a hash in Ruby?
  17. Accessing elements of nested hashes in ruby [duplicate]
  18. How do I create a SHA1 hash in ruby?
  19. Convert array of 2-element arrays into a hash, where duplicate keys append additional values
  20. How to assign hash[‘a’][‘b’]= ‘c’ if hash[‘a’] doesn’t exist?
  21. Is order of a Ruby hash literal guaranteed?
  22. How do methods use hash arguments in Ruby?
  23. How do I compare two hashes?
  24. Gem installation error: You have to install development tools first (Windows)
  25. You have already activated X, but your Gemfile requires Y
  26. How to avoid “cannot load such file — utils/popen” from homebrew on OSX
  27. what is ||= in ruby? [duplicate]
  28. Multi-Line Comments in Ruby?
  29. Matching balanced parenthesis in Ruby using recursive regular expressions like perl
  30. How can I get the absolute URL when extracting links using Nokogiri?

Leave a Comment