Merge hash with array values to one array

Question

How to merge hash with array values to one array:

h = {
    one: ["one1", "one2"],
    two: ["two1", "two2"]
}

after merge should be:

["one1","one2","two1","two2"]

is the order important? or is ["two1", "two2", "one1", "two2"] acceptable? — tokland
– tokland, Commented Apr 18, 2013 at 12:39

brymck · Accepted Answer · 2013-04-18 12:41:37Z

2

h.values.flatten
# => ["one1", "one2", "two1", "two2"]

You can do the same for the keys, of course. The only reason you need flatten here is because the values are themselves arrays, so h.values alone will return [["one1", "one2"], ["two1", "two2"]].

Also, just as an FYI, merge means something different (and pretty useful) in Ruby.

If you want to make sure it flattens only one level (per @tokland's comment), you can provide an optional argument to flatten such as with flatten(1).

edited Apr 18, 2013 at 12:41

answered Apr 18, 2013 at 12:29

brymck

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3 Comments

tokland Over a year ago

nit-pick: flatten(1) is more precise.

brymck Over a year ago

@tokland Depends on the situation, as it's not currently clear that the OP wants to flatten one level. I'll add a note, though.

tokland Over a year ago

Yeah. My point is that flatten is overused. A lots of times we only need to flatten one level and still we call a recursive flat. Maybe the OP has nested arrays, but in this case he would (should've) put it in the example. Just a detail, nothing more.

Nakilon · Accepted Answer · 2013-04-18 12:59:52Z

2

h.flat_map &:last
=> ["one1", "one2", "two1", "two2"]

answered Apr 18, 2013 at 12:59

Nakilon

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1 Comment

Arup Rakshit Over a year ago

Good one. I am late to post. Due to fill the CAPTCHA of SO Are you Robot :(

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