Check if all values from array start with a string

Question

I have an array of links:

urls =
[
  ["http://s3.amazonxaws.com/bb_images/uk/media_images/2/1-veXRiLqrxPbguaxFIcFbPA.png"],
  ["http://s3.amazonaws.com/bb_images/uk/media_images/2/1-veXRiLqrxPbguaxFIcFbPA.png"]
]

How can I return true if all links start with "http://s3.amazonaws.com"?

I tried:

if urls.any? { |url| url.include?('http://s3.amazonaws.com/') }
     #execute code
else
     #execute else code
end

But it does not return true or false in cases.

sawa · Accepted Answer · 2015-12-03 16:35:46Z

5

urls.flatten.all?{|s| s.start_with?("http://s3.amazonaws.com")}

answered Dec 3, 2015 at 16:35

sawa

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Comments

sawa · Accepted Answer · 2015-12-03 16:55:17Z

4

@sawa's code works. However, the following is a more efficient version.

compare_against = "http://s3.amazonaws.com"
urls.all?{|url_array| url_array[0].start_with?(compare_against)}

edited Dec 3, 2015 at 16:55

sawa

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answered Dec 3, 2015 at 16:42

djaszczurowski

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6 Comments

sawa Over a year ago

Good point about using a predefined string (and for avoiding an intermediate array). However, you can do that also by using the freeze optimization in string literals. start_with?("http://s3.amazonaws.com".freeze).

djaszczurowski Over a year ago

You're right about freeze. In that case I wanted to avoid temporary array, because it requires 2 iterations (the first to create it, and the second to verify predicate).

Sebastian Corneliu Vîrlan Over a year ago

Work's great, thank you, but the problem now is that compare_against = ["http://s3.amazonaws.com", Rails.root] , and I tried with each inside but every time is true

djaszczurowski Over a year ago

explain, what in your context compare_against = ["http://s3.amazonaws.com", Rails.root] means. Whether it's enough if string starts with any of compare_against, or it has to match all of them

Sebastian Corneliu Vîrlan Over a year ago

If my string start with s3.amazonaws.com or RAILS.root (RAILS.root is current url domain) should return true.

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