Ruby can't convert Array to Integer - ruby-on-rails

Question

I'm getting this error:
TypeError in Properties#show
At line #67 in /Users/taylor/Pro/rentroll_analysis/app/views/properties/show.html.erb, where this exception is raised:
can't convert Array into Integer
This is the extracted source around line #67:
64: <td><%=u.unit_number%></td>
65: <td><%=u.unit_type%></td>
66: <td><%=number_to_currency(u.market_rent - u.current_rent)%></td>
67: <td><%=number_to_currency(u.market_rent - u.current_rent)*(session[:assumptions]= [:spread_x])%></td>
68:
69: </tr>
70: <%end%>
When running this:
def setup_assumptions
if session[:assumptions].nil?
session[:assumptions]=[:min_spread=>400,:spread_x=>10]
end
end
I'm sure it's relatively simple but I can't figure it out.

Answer 1

If you're trying to set it to a map, use a map (curly braces) not an array (square brackets):
session[:assumptions] = { :min_spread => 400, :spread_x => 10 }
Otherwise you're setting session[:assumptions] to an array with a hash in it.
Also, what is your goal here?
number_to_currency(u.market_rent - u.current_rent) * (session[:assumptions]= [:spread_x])
I think you mean:
number_to_currency(u.market_rent - u.current_rent) * session[:assumptions][:spread_x]

Answer 2

When you save something to your session it saves it as a string, so when you're pulling something back from the session and want to perform Integer methods on it, you'll likely have to specify that it's an integer.
Doing something like: session[:assumptions][:spread_x].to_i to use your session content as an integer. Also, please note I think you have an errant = in your original code.
Lastly, you might not run into this, but I've sometimes had trouble using nested symbols in session variables. As in session[:assumptions][:spread_x]. I've sometimes had to change this to something like session[:assumptions]['spread_x'] and call the nested variable with a string instead.
Good luck!