Hi,
I have some code as follow.
class Loan
include DataMapper::Resource
belongs_to :loaner, Person, :key => true
belongs_to :loanee, Person, :key => true
property :currency, Enum[*CURRENCY_CODES], :key => true
property :amount, Decimal, :scale => 2, :default => 0
def self.count!(money_flow)
loan = get(money_flow.currency, money_flow.giver_id, money_flow.receiver_id)
loan.amount += money_flow.amount
end
# more code...
end
class MoneyFlow
include DataMapper::Resource
belongs_to :giver, Person
belongs_to :receiver, Person
property :id, Serial
property :amount, Decimal, :scale => 2, :min => 0.01
property :currency, Enum[*CURRENCY_CODES], :default => :CNY
# more code...
end
When I test the "count!" class method as follow:
describe "#count!" do
subject { lambda { Loan.count!(money_flow) } }
context "when a loan exists from giver to receiver" do
let!(:loan) { Loan.gen }
let(:money_flow) { MoneyFlow.gen(:giver => loan.loaner, :receiver =>
loan.loanee, :currency => loan.currency) }
it { should_not change(Loan, :count) }
end
end
It tells me I got a Immutable Error. I feel strange on that. They have keys,
and I didn't destroy the record. Can you see why? Thanks.
1) Loan#count! when a loan exists from giver to receiver
Failure/Error: subject { lambda { Loan.count!(money_flow) } }
DataMapper::ImmutableError:
Immutable resource cannot be modified
# ./lib/models.rb:49:in `count!'
# ./spec/models_spec.rb:59:in `block (4 levels) in <top (required)>'
# ./spec/models_spec.rb:63:in `block (4 levels) in <top (required)>'
On Jan 10, 2011, at 11:34 PM, Ted Han wrote:
> Objects are immutable when they've been deleted or frozen for some reason.
> Deleting a record from your data store will always result in that record
> being frozen.
>
> Is there a specific problem that you're having?
>
> -T
>
> On Mon, Jan 10, 2011 at 10:23 AM, Zhi-Qiang Lei <[email protected]>
> wrote:
> Dear All,
>
> Could anyone answer me when a resource should be immutable? And why? Thanks.
>
> Best regards,
> Zhi-Qiang Lei
> [email protected]
>
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Best regards,
Zhi-Qiang Lei
[email protected]
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