Ruby - Extract value of a particular key from array of hashes

Question

I have an array of hashes - @profiles which has data as:

[{:user_id=>5, :full_name=>"Emily Spot"},{:user_id=>7, :full_name=>"Kevin Walls"}]

I want to get full_name of say user_id = 7? I'm doing the following: but it's throwing an error that expression @profiles.find{|h| h[':user_id'] == current_user.id} is nil.

name = @profiles.find{ |h| h[':user_id'] == current_user.id }[':full_name']

if I use select instead of find then error is - no implicit conversion of String into Integer.

How do I search through the array of hashes?

UPDATE:

After @Eric's answer, I restructured my job model & view actions:

 def full_names profile_arr||= [] profile_arr = self.applications.pluck(:user_id) @profiles = Profile.where(:user_id => profile_arr).select([:user_id, :first_name, :last_name]).map {|e| {user_id: e.user_id, full_name: e.full_name} } @full_names = @profiles.each_with_object({}) do |profile, names| names[profile[:user_id]] = profile[:full_name] end end

In the view....,

p @current_job.full_names[current_user.id]

Andrey Deineko · Accepted Answer · 2017-04-03 11:58:13Z

7

@profiles is an array of hashes, with symbols as keys, whereas what you use is String objects.

So ':user_id' is a string, and you want symbol: :user_id:

@profiles.find{ |h| h[:user_id] == current_user.id }

I want to get full_name of say user_id == 7

@profiles.find { |hash| hash[:user_id] == 7 }.fetch(:full_name, nil)

Note, I used Hash#fetch for case, when there is no hash with value 7 at key :user_id.

edited Apr 3, 2017 at 11:58

answered Apr 3, 2017 at 11:00

Andrey Deineko

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5 Comments

Means Over a year ago

Oh yes, silly me....that quote was a mistake. Thx. OK so you mean the safe operator will bypass if value of expression is nil ?

Andrey Deineko Over a year ago

@Means yea, so if @profiles.find { |hash| hash[:user_id] == 7 } returns nil, without safe navigation calling name on it will raise an exception,whereas with safe navigation it will just return nil

Andrey Deineko Over a year ago

@Means nil&.non_existing_method => nil

Means Over a year ago

Sorry, Andrey, but the '&.full_name' threw an error : undefined method `full_name' for {:user_id=>5, :full_name=>"Emily Spot"}:Hash. Only when I append [:full_name] to that @profile.find expression, it works. Any idea?

Andrey Deineko Over a year ago

@Means my bad, I edited the answer, you are 100% correct, you can't run full_name on a hash, because it does not implement that method.

Eric Duminil · Accepted Answer · 2017-04-03 11:14:10Z

As you've noticed, it's not very convenient to extract the name of user_id 7. You could modify your data structure a bit :

@profiles = [{:user_id=>5, :full_name=>"Emily Spot"}, {:user_id=>7, :full_name=>"Kevin Walls"}] @full_names = @profiles.each_with_object({}) do |profile, names| names[profile[:user_id]] = profile[:full_name] end p @full_names # {5=>"Emily Spot", 7=>"Kevin Walls"} p @full_names[7] # "Kevin Walls" p @full_names[6] # nil

You didn't lose any information but name look-up is now much faster, easier and more robust.

Eric, this is an out-of-the-box answer....and actually perfectly worked for me as I have moved the full_names now to controller. I've edited into my original question to show how I structured it before and now applied your inputs.
@Means: Good to know. You probably should put this logic in the model though.
Can you suggest if @profiles SQL query in my original question -UPDATE part, can be improved/optimized without that long 'select...map' combination?
@Means after your edit it is obvious, that this logic should go to the model. You should think about setting up proper associations.

michaeldever · Accepted Answer · 2017-06-21 13:09:12Z

Suggesting, to create a new hash that can make things simpler

Eg:

results = {} profiles = [ {user_id: 5, full_name: "Emily Spot"}, {user_id: 7, full_name: "Kevin Walls"} ] profiles.each do |details| results[details[:user_id]] = details[:full_name] end

Now, results will have:

{5: "Emily Spot", 7: "Kevin Walls"}

So, if you need to get full_name of say user_id = 7, simply do:

results[7] # will give "Kevin Walls"

Michael, you didn't really answer the question. You need to give a solution that returns a specific user's full name. Your answer is close, but I'm going to downvote it until you get a chance to edit or delete your answer.

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