Re: How to compare a hash key with a string value

A few remarks inline below.

On Wed, Oct 23, 2019 at 7:36 PM Tran, Minh <[email protected]>
wrote:

> Hello,
>     I am having a scenario which I want to print out the value of a hash
> element when its key equals to a string value such as "width".
> I try several alternatives but so far I have had a good result.
> So if you know on how to do , please share it with me.
>
> My hash table array looks like as the following:
>
> hash =
> [{"label":"Name","value":"Bob","identifier":"field2","type":"oneLineText","page":1,"page_name":"Step
> 1","width":"100%"},{"label":"Email","value":"[email protected]","identifier":"field3","type":"email","page":1,"page_name":"Step
> 1","width":"100%"},{"label":"Phone
> Number","value":"","identifier":"field7","type":"oneLineText","page":1,"page_name":"Step
> 1","width":"100%"},{"label":"Comments","value":"some information about the
> compagny","identifier":"field5","type":"textarea","page":1,"page_name":"Step
> 1","width":"100%"}]
>

The name of the variable is misleading. This is actually an Array of Hash,
so "hashes" would be more appropriate.


> My Ruby code is as the following where I need to print out the hash value
> when the hash key equals to "width"
>
>
> i = 0
> hash.each do |person|
>  i += 1
>  puts "Person is #{i}"
>  person.each do |key, value|
>

You are not actually using the Hash as a hashtable with fast lookups here.


>
>     if key == "width"
>       puts "The value of width is #{value}"
>     end
>
>
>   end
> end
>
>
I would do

hashes.each_with_index do |h, i|
  puts "Person: #{i}"
  width = h["width"] and puts "The value of width is #{width}"
end

This is more efficient than checking with #has_key? because it requires
just a single hash lookup vs. two. If you want a printout also for nil and
false you could do

hashes.each_with_index do |h, i|
  puts "Person: #{i}"
  match = h.assoc(:width) and puts "The value of width is #{match.last}"
end

Cheers

robert


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