How to calculate the hash for a payment form? - ruby-on-rails

Question

I'm trying to calculate a hash for a payment form but I get the error:
no implicit conversion of Fixnum into String
so I interpret this that I'm trying to do math calculation on what is text. But how should I correct my code?
The instructions from the payment merchant are:
hash = SHA1(salt + "|" + description + "|" + amount + "|" + currency +
"|" + transaction_type)
So in my controller I have:
def checkout
#organization = Organization.new(organizationnew_params)
if #organization.save
#organization.members.each do |single_member|
single_member.send_activation_email
end
#amount = 100.00
#currency = "EUR"
#description = #organization.id
#transaction_description = "My description"
#transaction_type = "S"
### LINE BELOW HAS THE HASH, WHICH REFERS TO THE PRIVATE METHOD BELOW ###
#hash = hash(#description, #amount, #currency, #transaction_type)
render 'checkout'
else
render 'new_premium'
end
end
private
def hash(description, amount, currency, transaction_type)
#hash = SHA1(SALT + "|" + description + "|" + amount + "|" + currency + "|" + transaction_type)
end
In an initializer I have defined SALT (as well as my merchant_id which is used in the form that is posted to the merchant in the checkout view).

Answer 1

Writing this will be better.
hash = SHA1([salt, description, amount.to_s, currency,transaction_type].join("|"))

Answer 2

You interpreted it wrongly, it's the other way round. You're trying to use a number as a string.
Try to explicitely convert the number in to a string, like so:
#hash = SHA1(SALT + "|" + description + "|" + amount.to_s + "|" + currency + "|" + transaction_type)
As I don't know what all the variables' types are, you might have to add another to_s to a non-string.

Answer 3

The error indicates that you are adding a number to a string, I think the problem is that "amount" is a number which you are adding to a string. you just have to change that:
#hash = SHA1(SALT + "|" + description + "|" + amount.to_s + "|" + currency + "|" + transaction_type)
the :to_s method will convert amount into string. (if there are other numbers just do the same.)
Or you can do this with string interpolation:
#hash = SHA1("#{SALT}|#{description}|#{amount}|#{currency}|#{transaction_type}")