calculate number in views ruby on rails - ruby-on-rails

Question

I would like to calculate mid test and final test mark into a grade. E.g.:
mid test = 80 , final test = 80
(midtest + finaltest)/2 >=80
grade = "A"
Is it possible to do an if condition in views and insert into database? Something like:
if (midtest + finaltest) / 2 >= 80
grade = "A"
elsif (midtest + finaltest)/2 >= 70 and < 80
grade = "B"
elsif (midtest + finaltest) /2 >= 60 and < 70
grade = "C"
So that in views we don't need a text_field for grades and so that the calculation is automatically inserted into the database.
This is the solution
Controller
def create
#nilai = Nilai.new(params[:nilai])
#nilai.get_grade
respond_to do |format|
if #nilai.save
format.html { redirect_to #nilai, notice: 'Nilai was successfully created.' }
format.json { render json: #nilai, status: :created, location: #nilai }
else
format.html { render action: "new" }
format.json { render json: #nilai.errors, status: :unprocessable_entity }
end
end
end
Model
class Nilai < ActiveRecord::Base
attr_accessible :grade, :id_makul, :id_mhs, :id_nilai, :uas, :uts
def get_grade
#calculate = (self.uas + self.uts)/2
if #calculate >= 80
self.grade = "A"
elsif #calculate >=70 and #calculate < 80
self.grade = "B"
elsif #calculate >=60 and #calculate <70
self.grade = "C"
elsif #calculate >=50 and #calculate <60
self.grade = "D"
else
self.grade = "E"
end
end
end

Answer 1

Still guessing what you really want and why you think you have to do it in the view...
As I said above, Views should be used solely for code that displays data that already exists. Code that inserts things into the database is for your models and controllers.
I suggest either:
1) you create a method on your model called "grade" eg:
def grade
if (midtest + finaltest) / 2 >= 80
return "A"
elsif (midtest + finaltest)/2 >= 70 and < 80
return "B"
elsif (midtest + finaltest) /2 >= 60 and < 70
return "C"
else
return "F"
end
end
now, you can call this method from your view eg:
Grade: <%= #my_model.grade %>
Note that this method does not insert it into the database.
OR
2) you create a method as above on a before_save callback
eg lets say you're storing it into the "grade" column in the db:
class MyModel < ActiveRecord::Base
before_create :calculate_grade
def calculate_grade
if (midtest + finaltest) / 2 >= 80
self.grade = "A"
elsif (midtest + finaltest)/2 >= 70 and < 80
self.grade = "B"
elsif (midtest + finaltest) /2 >= 60 and < 70
self.grade = "C"
else
self.grade = "F"
end
end
end
And now whenever your model gets saved, the grade gets re-calculated from the test scores and saved into the db alongside.
so you can use "grade" in your views as above, but it's coming from the database column
Grade: <%= #my_model.grade %>

Answer 2

technically you could do almost anything in views, after all view is also a ruby file. So you could have conditions, DB connections etc..
BUT, Its not a good practise to have your logic in your views. Always try to have your view to display only. All the processing logic should be in Models
Idea is, Fat models, thin controllers are views are only for presentation. So in your case try and see at least to get your login in to a helper method.
One more thing I notice, you could have this line
(midtest + finaltest) / 2
to
average_marks = (midtest + finaltest) / 2
and use average_marks, in other places, as its more DRY (Dont Repeat Yourself)
HTH :)