Question

I’m trying to create a hash with an array inside:

# create new hash to store customers and their projects
@customers = Hash.new

# get all customers from Mite
Mite::Customer.all.each do |customer|
  @customers[customer.id] = {:name => customer.name, :projects => []}
end

# get all projects from Mite and store them in the :projects array
Mite::Project.all.each do |project|
  @customers[project.customer_id][:projects] << project # line 17
end

Mite::Project.all and Mite::Customer.all are methods for an external API (mite.yo.lk). They work and i get data back, so thats not the failure.

Unfortunately, i have to go this way, cause the API doesn’t have any methods to filter projects by the customer id.

That’s the error message:

undefined method `[]' for nil:NilClass

and

app/controllers/dashboard_controller.rb:17:in `block in index'
app/controllers/dashboard_controller.rb:16:in `each'
app/controllers/dashboard_controller.rb:16:in `index'

I don’t understand whats wrong here?

Answer 1

what @thorstenmüller said is correct. Looks like the Projects contains references to stale customers?

I would recommend defensive coding, provided it does not introduce logical errors. Something like:

# get all projects from Mite and store them in the :projects array
Mite::Project.all.each do |project|
  if @customers[project.customer_id].present?
    @customers[project.customer_id] << project
  end
end

Again, I would only recommend this if stale customers are acceptable in your database.

Another thing to look out for is that project.customer_id is a consistant type (i.e. always an Integer or String):

# get all customers from Mite
Mite::Customer.all.each do |customer|
  @customers[customer.id.to_i] = {:name => customer.name, :projects => []}
end

and

# get all projects from Mite and store them in the :projects array
Mite::Project.all.each do |project|
  @customers[project.customer_id.to_i][:projects] << project # line 17
end

I have personally been caught out on this far too many times.

HTH and best.