Array of Arrays, delete an index based on the contents of the array at the index?

Question

I've been struggling learning how to deal with arrays made up of arrays.

Say I had this array:

my_array = [['ORANGE',1],['APPLE',2],['PEACH',3]

How would I go about finding the my_array index that contains 'apple' and deleting that index (removing the sub-array ['APPLE',2] because 'apple' was conatined in the array at that index) ?

Thanks - I really appreciate the help from here.

miku · Accepted Answer · 2011-02-05 02:14:28Z

7

You can use Array.select to filter out items:

>> a = [['ORANGE',1],['APPLE',2],['PEACH',3]]
=> [["ORANGE", 1], ["APPLE", 2], ["PEACH", 3]]

>> a.select{ |a, b| a != "APPLE" }
=> [["ORANGE", 1], ["PEACH", 3]]

select will return those items from the, for which the given block (here a != "APPLE") returns true.

answered Feb 5, 2011 at 2:14

miku

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DigitalRoss · Accepted Answer · 2011-02-05 02:16:57Z

6

my_array.reject { |x| x[0] == 'APPLE' }

answered Feb 5, 2011 at 2:16

DigitalRoss

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4 Comments

DigitalRoss Over a year ago

Tho I think The MYYN's deconstructing yield (I think that's what it's called) is nice.

miku Over a year ago

A variation of this: a.reject { |x, y| x == 'APPLE' }

DigitalRoss Over a year ago

Girish Rao, that's fine, good point. I suppose, for practice, I could argue that reject will work for any Enumerable and not just Array, but that argument could cut both ways: since delete_if is implemented only for Array you can probably count on it running quickly.

the Tin Man Over a year ago

You'll find reject and its counterpart select used a lot more than delete_if. I think it's because they're more generic, used more often, and easier to remember as a result.

Girish Rao · Accepted Answer · 2011-02-05 02:39:52Z

4

I tested this, it works:

my_array.delete_if { |x| x[0] == 'APPLE' }

edited Feb 5, 2011 at 2:39

answered Feb 5, 2011 at 2:19

Girish Rao

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1 Comment

Reno Over a year ago

Using delete_if seems really human readable to me. I love this place - 3 almost instant answers all different and all of them work. I learned a lot - thanks all!

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