Chaining array into new split function call

Question

I have the following and am trying to split on '.' and then split the returned first part on '-' and return the last of the first part. I want to return 447.

a="cat-vm-447.json".split('.').split('-')

Also, how would I do this as a regular expression? I have this:

a="cat-vm-447.json".split(/-[\d]+./)

but this is splitting on the value. I want to return the number.

I can do this:

a="cat-vm-447.json".slice(/[\d]+/)

and this gives me back 447 but would really like to specify that the - and . surround it. Adding those in regex return them.

Aliaksei Kliuchnikau · Accepted Answer · 2012-01-25 18:49:39Z

3

First question. Split returns an array, so you need to use Array#[] to get first(0) or last(-1) elements of this array. Alternatives is Array#first and Array#last methods.

a="cat-vm-447.json".split('.')[0].split('-')[-1] # => "447"

Second question. You can match your number into group and then get it from the response (it will have index 1. Item with index 0 will be full match ("-447." in your case). You can use String#[] or String#match (among others) methods to match your regex.

"cat-vm-447.json"[/-(\d+)\./, 1] # => "447"
# or
"cat-vm-447.json".match(/-(\d+)\./)[1] # => "447"

edited Jan 25, 2012 at 18:49

answered Jan 25, 2012 at 18:44

Aliaksei Kliuchnikau

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2 Comments

the Tin Man Over a year ago

If the filename is guaranteed to only have one string of digits, "cat-vm-447.json"[/\d+/] will return "447" without the need to use a capture.

Aliaksei Kliuchnikau Over a year ago

@theTinMan, yes, but OP would really like to specify that the - and . surround it (from the question)

Gazler · Accepted Answer · 2012-01-25 18:43:43Z

1

Split returns an array, so you need to specify the index for the next split.

a="cat-vm-447.json".split('.').first.split('-').last

For the regular expression, you need to wrap what you want to capture in parentheses.

/-(\d+)\./

answered Jan 25, 2012 at 18:43

Gazler

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Comments

Mike · Accepted Answer · 2012-01-25 18:42:51Z

0

a = "cat-vm-447.json"
b = a.match(/-(\d+)\./)
p b[0] # => 447

answered Jan 25, 2012 at 18:42

Mike

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Comments

Mathieu Mahé · Accepted Answer · 2012-01-25 18:43:43Z

0

Try something like that:

if "cat-vm-447.json" =~ /([\d]+)/
   p $1
else
   p "No matches"
end

The parentheses in the regex extract the result in the $1 variable.

answered Jan 25, 2012 at 18:43

Mathieu Mahé

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Comments

evfwcqcg · Accepted Answer · 2012-01-25 18:49:01Z

0

When you split your string second time, you actually trying to split Array instead of String.

ruby-1.9.3-head :003 > "cat-vm-447.json".split('.')
# => ["cat-vm-447", "json"]

In regexp case, you can use /[-.]/

ruby-1.9.3-head :008 > "cat-vm-447.json".split(/[-.]/)
# => ["cat", "vm", "447", "json"] 
ruby-1.9.3-head :009 > "cat-vm-447.json".split(/[-.]/)[2]
# => "447"

answered Jan 25, 2012 at 18:49

evfwcqcg

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