Question

I am facing problems generating a loop in Ruby that is to be pushed to a GAMS include file. It should display each tuple of a c(i,j) vector, for all i and j, i. e.

Parameter c(i,j) /
c('i1','j1')=[value];
c('i1','j2')=[value];
.
.
.
c('iI','jJ')=[value];
/

The problem is, that there are three entities to fetch data from, so that I struggle to identify the respective distance between warehouses and clients. This is the loop so far:

printf(f, "Parameter c(i,j) / \n")
@warehouses.each { |wh| printf(f, "c('i" + wh.id.to_s + "',") +
@clients.each { |cl| printf(f, "'j" + cl.id.to_s + "')=") +
@transquans.distance.to_s(@warehouses, @clients) + "; \n"
}
}

The structure behind that is uploaded here.

The error message returned is like this: “undefined method `distance’ for nil:NilClass”.

Answer 1

It’s solved by now!

printf(f, "Parameter c(i,j) / \n")
@warehouses.each do |wh|
  @clients.each do |cl|
    transquan = Transquan.where(:warehouse_id => wh.id, :client_id => cl.id).first
    if transquan.nil?
    else
      printf(f, "c('i" + wh.id.to_s + "' , 'j" + cl.id.to_s + "')=" + transquan.distance.to_s + ";\n")
    end
  end
end