Rails conditional CSS in view helper - css

Question

I have a simple rails app and I'm trying to write a view helper that does the following.
Compares two values. If the current_month amount is greater than the forecast amount then make the text green. If the current_month amount is less than the forecast amount then make the text red.
I wrote out this simple helper to append text to the output of the the rails method, but I'm unsure of how to inject CSS/styling into this.
def target_hit(forecast, current)
(if current.amount > forecast.amount
number_to_currency(current.amount.to_s) + " Yay"
elsif current.amount < forecast.amount
number_to_currency(current.amount.to_s) + " No dice"
end).html_safe
end
I'm pretty proficient on the backend but when it comes to front-end stuff I'm stumbling a lot. Any help would be greatly appreciated.
example view code
<p class='total'>Current: <%= target_hit(#forecast, #current) %></p>

Answer 1

The rails helper content_tag http://apidock.com/rails/ActionView/Helpers/TagHelper/content_tag, is useful and means you don't have to use html_safe. I try to move all the logic from the views to helpers to make the view easy to read e.g.
def target_hit(current_amt, forecast_amt)
content_tag(:p, "#{number_to_currency(current_amt.to_s)} target_content(current_amt, forecast_amt)", class: "total #{target_class(current_amt, forecast_amt)}")
end
def target_content(current_amt, forecast_amt)
forecast_reached?(current_amt, forecast_amt) ? "Yay" : "No dice"
end
def target_class(current_amt, forecast_amt)
forecast_reached?(current_amt, forecast_amt) ? "green" : "red"
end
def forecast_reached?(current_amt, forecast_amt)
current_amt >= forecast_amt
end
in the view, you just call the helper method
<%= target_hit(#current.amount, #forecast.amount) %>