CODEWITHSUNDEEP
ruby
srivani
srivani

Reputation: 61

Convert string to variable name in ruby

I have variables

 <% mon_has_two_sets_of_working_hours = 0 %>
 <% tue_has_two_sets_of_working_hours = 0 %>
 <% wed_has_two_sets_of_working_hours = 0 %>

I want to change the values of these variables dynamically.

 <% days_array = ['mon', 'tue', 'wed'] %>

 <% days_array.each do |day| %>
   <% if condition? %>
    # here i want to set %>
     <% "#{day}__has_two_sets_of_working_hours" = 1 %>
  end
 end

The value is not getting assigned. Is there any way to assign value to variable dynamically?

Upvotes: 6

Views: 12625

Answers (3)

betacar
betacar

Reputation: 426

Now, I know this question is a bit old, but there is an easier way to do this and is using the standard Ruby send method. This is actually one of the methods that make Ruby so agile in the metaprogramming world.

This is actually a config setting I use in a Rails app:

# In a YAML    
twitter:
  consumer_key: 'CONSUMER-KEY'
  consumer_secret: 'CONSUMER-SECRET'
  oauth_token: 'OAUTH-KEY'
  oauth_token_secret: 'OAUTH-SECRET'

...

# And in your file.rb
config = YAML.load_file(Rails.root.join("config", "social_keys.yml"))[Rails.env]['twitter']

Twitter.configure do |twitter|
  config.each_key do |k|
    twitter.send("#{k}=", config[k])
  end
end

It's DRY and very easy to understand. :)

Upvotes: 2

jvillian
jvillian

Reputation: 20263

Yet another answer to this old question.

In my scenario, I wanted to count how many times a day showed up in an array of days (day_array). I didn't need to know if a day didn't show up in day_array, so I didn't initialize the days_count hash as gunn did in his answer.

Here's how I did it:

def count_days(day_array)
  days_count = {}
  day_array.each do |day|
    days_count[day].nil? ? days_count[day] = 1 : days_count[day] = days_count[day] + 1
  end
  puts days_count
end

If I copy and paste the above in irb, then:

> count_days(%w[SU MO])
{"SU"=>1, "MO"=>1}

> count_days(%w[SU SU MO])
{"SU"=>2, "MO"=>1}

Basically, consistent with prior answers. But, I thought an additional example couldn't hurt.

Upvotes: 0

gunn
gunn

Reputation: 9165

I don't think there is a way to do this. There is with instance or class variables, but with local variables there is very rarely a good need.

In your case you really should have the data in a hash. Also, logic like this really does not belong in erb. You want something like:

working_hour_sets = %w[mon tue wed thu fri sat sun].inject({}) do |hash, day|
  hash[day]=0;
  hash
end
# puts working_hour_sets #=> {"wed"=>0, "sun"=>0, "thu"=>0, "mon"=>0, "tue"=>0, "sat"=>0, "fri"=>0}

working_hour_sets.each do |day, value|
  working_hour_sets[day] = 1 if condition?
end

Upvotes: 4

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