On 8/7/06, Yochen G. [email protected] wrote:
So if I do understand you all correctly, in Ruby you put the
responsible to the caller of a method (eg print_salary()). If you want
to test that method, you test it only with the proper types.
Where type may not be related to the Object’s class or inheritance tree.
An object’s type for any method call is explicitly related to whether it
responds to the method we’re looking for with the arguments we provide
and the sort of return value we’re wanting. It’s significantly different
than Java in this way.
The next thing would be testing the method which includes the call of
print_salary() if it calls this methods with the wrong types of
parameter. Is this right?
Um, not really as I understand it.
One problem in this concept is that if some operations might work on a
parameter-object and the following is not the exception is thrown when
the object is already modified.
There are problems with your example code:
class Bank
@invitations_to_golf
This won’t do what you expect. Try:
def handle_client_well client
client.decrease_acoount(200)
client.check_portfolio
@invitations_to_golf.push client
endend
class Bank
def initialize
@invitations_to_golf = []
end
def issue_golf_invitations(title, sender, message, date)
@invitations_to_golf.each { |client|
client.send_message title, sender, message, date
}
end
def treat_client_well(client)
if client.check_portfolio
client.decrease_account(200)
@invitations_to_golf << client
end
end
end
What this does is that it requires that all clients have a
#check_portfolio method. If the Bank’s clients aren’t guaranteed to have
that, you’ll blow up here, as you’ve suggested. But how do you deal with
that? Well, you don’t look for a VeryRichClient. You do one of two
things:
class Client
def check_portfolio
nil
end
end
class LowBudgetClient < Client
end
class VeryRichClient < Client
def check_portfolio
true
end
end
So you modify the object you’re dealing with and expect to pass in so
that it always has a check_porfolio (that’s why I put the “if” test,
which you’d want anyway) or you do:
class Bank
def treat_client_well(client)
if client.respond_to?(:check_portfolio) and client.check_portfolio
client.decrease_account(200)
@invitations_to_golf << client
end
end
end
Or you handle your call a bit better:
jon_doe = LowBudgetClient.new
big_boss = VeryRichClient.new
big_money = Bank.new
big_money.handle_client_well big_boss
big_money.handle_client_well jon_doe rescue nil
One need not be explicit about how you handle a lot of things in Ruby.
Strictly speaking, you’d never want to have two classes for clients in
this way, but you may have things in the contents of the clients which
allow you to do things smarter.
-austin