Array detect method - return the value of a specific sub-array index?

Question

(ruby 1.86)

I have an array made up of arrays like:

>> myArray 
=> [["apple", 1], ["bananna", 2], ["peach", 3], ["orange", 4]]

I know I can use the detect method to find the first instance of 'orange' in index[0] of the sub-arrays in MyArray:

myTest = (myArray.detect { |i| i[0] == 'orange' } || []).first
=> orange

If it's possible, how can I have the detect method return the value of the sup-array index position 1. Like, i[0] is being returned, but when i[0] == 'orange' I need i[1] returned.

I need to search for 'orange' and have the return value be 2.

Thank You!

Why do you want the return value to be 2? Given your description, I would have thought you want 4. — Mark Thomas
– Mark Thomas, Commented Jan 31, 2011 at 13:59

steenslag · Accepted Answer · 2011-01-31 14:08:20Z

3

I suppose you want the return value to be 4. No need for #detect:

ar = [["apple", 1], ["bananna", 2], ["peach", 3], ["orange", 4]]
puts ar.assoc("orange").last

#=> 4

answered Jan 31, 2011 at 14:08

steenslag

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3 Comments

Mark Thomas Over a year ago

Nice! +1. I always forget about assoc, as I've never found a need for it.

Reno Over a year ago

You know just reading the API I would have never figured the ".last" part out. There's no mention of how to point to a specific index of the sub-array that's found with the match. I guess if you understand arrays really well that kind of thing just comes to you? Again - thanks a bunch!

steenslag Over a year ago

@Reno ar.assoc("orange")[1] is the same thing here.

Mark Thomas · Accepted Answer · 2011-01-31 14:16:51Z

2

I'd recommend using a hash. It better suits the usage you describe, and will be faster for large amounts of data.

fruit = {'apple'=>1, 'banana'=>2, 'peach'=>3, 'orange'=>4, 'kiwi'=>42}

puts fruit['orange'] #=> 4

But if you really want to retrieve the value from your subarray, change your first to last:

myTest = (myArray.detect { |i| i[0] == 'orange' } || []).last
#=> 4

Update: or even simpler, as @steenslag points out:

myTest = myArray.assoc("orange").last
#=> 4

edited Jan 31, 2011 at 14:16

answered Jan 31, 2011 at 14:06

Mark Thomas

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