arrays - Nil errors in creating a hash in Ruby on Rails -

i'm running several syntax , nil issues when trying create hash idea_benefit_count.

@idea = @domain.ideas @idea_evaluations = array.new() @idea.each |idea|   @idea_evaluations << idea.evaluations end  @idea_benefit = [] if !@idea_evaluations.nil?   @idea_evaluations.each |eval|     @idea_benefit << eval.benefit   end   @idea_benefit_count = hash.new(0)   @idea_benefit.flatten.each { |idea_benefit| @idea_benefit_count[idea_benefit] += 1 } end 

an idea has_many domains, @idea should of ideas has given @domain.

@idea_evaluations array of evaluations belong_to specific idea.

@idea_benefit array of arrays holds of each evaluation's benefit entries. example output: [["happier_customers"], ["happier_employees"], ["happier_employees", "decreased_costs"], ["happier_employees"]]

idea_benefit_count reads idea_benefit , counts how many of each type of benefit idea has. output of idea_benefit_count based on above idea_benefit array {"happier_customers"=>1, "decreased_costs"=>1, "happier_employees"=>3}

(hopefully context covers everything)

my current error undefined method 'benefit' on line @idea_benefit << eval.benefit. benefit attribute of evaluation, should output ["happier_customers"].

i realize code bit of mess, suggestions super helpful on getting entire thing working. big problem checking see if there evaluations belonging idea, because if comes nil throws error. tried fix if !@idea_evaluations.nil? check, haven't been able test yet because of undefined method 'benefit' error.

edit

@idea_evaluations = array.new() @idea.each |idea|   @idea_evaluations << idea.evaluations end @idea_evaluations.flatten!  @idea_benefit = [] unless !@idea_evaluations.nil?   @idea_evaluations.each |eval|     @idea_benefit << eval.benefit   end   @idea_benefit_count = hash.new(0)   @idea_benefit.flatten.each { |idea_benefit| @idea_benefit_count[idea_benefit] += 1 } end 

the problem see if understand trying way dumping idea.evaluations @idea_evaluations.
@idea_evaluations going array of arrays of evaluations not array of evaluations think.
e.g. [[eval1,eval2],[eval3,eval4,eval5]] instead of [eval1, eval2, eval3, eval4, eval5]

when try access benefit, attempts benefit method array not exist.

try altering

@idea.each |idea|   @idea_evaluations << idea.evaluations end 

to be

@idea.each |idea|   @idea_evaluations << idea.evaluations end @idea_evaluations.flatten! 

also in ruby don't do

if !condition  

you

unless condition