Ruby on rails 从';之间的散列/差异获取属性;。第一';和';[i] &x27;
对于Ruby on rails 从';之间的散列/差异获取属性;。第一';和';[i] &x27;,ruby-on-rails,ruby,ruby-on-rails-3,hash,Ruby On Rails,Ruby,Ruby On Rails 3,Hash,对于goal def evals self.evaluations.order("eval_number").group_by(&:student_id) end def evals_for(student, i) @evals = [] self.evals.values.each do |eval| @evals << eval.keep_if { |e| e.student_id == student.id }
goal
def evals
self.evaluations.order("eval_number").group_by(&:student_id)
end
def evals_for(student, i)
@evals = []
self.evals.values.each do |eval|
@evals << eval.keep_if { |e| e.student_id == student.id }
end
@evals = @evals.reject { |array| array.empty? }.first
@evals[i]
end
我想获得分数,但当我调用class方法最后一行的@evals[I].score
时,我得到一个错误-未定义的方法“score”,表示nil:NilClass
我知道我不能在散列上调用类方法,但有没有办法只提取这些数据?作为一个子问题,我对调用
@evals时.first
和[I]
之间的区别有点困惑。first.score
返回“3”-只有我不能使用first,因为我需要能够依次访问evaluation
的每个实例 这不是一个简单的散列:
#<Evaluation id: 1949, score: 3, created_at: "2013-08-28 09:44:32", updated_at: "2013-08-28 09:44:32", student_id: 32, goal_id: 63, eval_number: 29>
#<Evaluation:x>, #<Evaluation:y>, #<Evaluation:z>
#<Evaluation id: 1949, score: 3, created_at: "2013-08-28 09:44:32", updated_at: "2013-08-28 09:44:32", student_id: 32, goal_id: 63, eval_number: 29>
#<Evaluation id: 1949, score: 3, created_at: "2013-08-28 09:44:32", updated_at: "2013-08-28 09:44:32", student_id: 32, goal_id: 63, eval_number: 29>
@evals[i].score if @evals[i]