Removing the key on currency only will lead to only one Loan record between two 
people, and they cannot have other Loan in different currency. So I remove all 
of them (keys), and add a id Serial property. With this validation, not 
ImmutableError recurs yet.
Do you think I should submit a ticket for this?


On Jan 14, 2011, at 7:39 AM, RipTheJacker wrote:

> Yes, the composite keys match your requirement, so you can leave them
> for the belongs_to associations. And I'm starting to think this may
> really be a bug. See if this works:
> 
> remove the :key => true from :currency and add this:
> validates_uniqueness_of :currency, :scope => [:loaner_id, :loanee_id]
> 
> On Jan 13, 1:53 am, Zhi-Qiang Lei <[email protected]> wrote:
>> Excuse me, a little more discussion please. In my past design, there should 
>> be ONLY ONE Loan record between two people in a specific currency. The 
>> composite keys match this requirement, don't they? But to make it immutable.
>> 
>> On Jan 13, 2011, at 3:17 AM, RipTheJacker wrote:
>> 
>> 
>> 
>>> Those won't make it immutable, but the key does need to be unique. So,
>>> unless you can only have ONE Loan per Person you should probably
>>> change those too. Rather than making them keys you probably mean to
>>> have them as indexes, which I DataMapper does for you, and add an :id
>>> Serial primary key to the model, the same as it is in your MoneyFlow
>>> model.
>> 
>>> On Jan 12, 12:28 am, Zhi-Qiang Lei <[email protected]> wrote:
>>>> Hi,
>> 
>>>> This model also has two more keys, they make a composite keys. This will 
>>>> also make it immutable?
>> 
>>>>>>>>   belongs_to :loaner, Person, :key => true
>>>>>>>>   belongs_to :loanee, Person, :key => true
>> 
>>>> On Jan 12, 2011, at 3:15 AM, RipTheJacker wrote:
>> 
>>>>> Ok. It's because of this:
>> 
>>>>>  property :currency, Enum[*CURRENCY_CODES], :key => true
>> 
>>>>> You can't have :key => true on an Enum property since it is not
>>>>> unique.
>> 
>>>>> On Jan 10, 11:22 pm, Zhi-Qiang Lei <[email protected]> wrote:
>>>>>> Hi,
>> 
>>>>>> I still get the error with your spec code, here is the backtrace.
>> 
>>>>>> Failures:
>> 
>>>>>>   1) Loan#count! when a loan exists from giver to receiver
>>>>>>      Failure/Error: Loan.count!(money_flow)
>>>>>>      DataMapper::ImmutableError:
>>>>>>        Immutable resource cannot be modified
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/dm-core-1.0.2/lib/dm-core/r
>>>>>>  esource/state/immutable.rb:16:in `set'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/dm-core-1.0.2/lib/dm-core/m
>>>>>>  odel/property.rb:251:in `amount='
>>>>>>      # ./lib/models.rb:49:in `count!'
>>>>>>      # ./spec/models_spec.rb:64:in `block (4 levels) in <top (required)>'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-expectations-2.4.0/li
>>>>>>  b/rspec/matchers/change.rb:17:in `call'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-expectations-2.4.0/li
>>>>>>  b/rspec/matchers/change.rb:17:in `matches?'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-expectations-2.4.0/li
>>>>>>  b/rspec/expectations/handler.rb:34:in `handle_matcher'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-expectations-2.4.0/li
>>>>>>  b/rspec/expectations/extensions/kernel.rb:50:in `should_not'
>>>>>>      # ./spec/models_spec.rb:63:in `block (3 levels) in <top (required)>'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:49:in `instance_eval'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:49:in `block (2 levels) in run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:98:in `with_around_hooks'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:46:in `block in run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:91:in `block in with_pending_capture'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:90:in `catch'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:90:in `with_pending_capture'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example.rb:45:in `run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:261:in `block in run_examples'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:257:in `map'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:257:in `run_examples'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:231:in `run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:232:in `block in run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:232:in `map'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/example_group.rb:232:in `run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/command_line.rb:27:in `block (2 levels) in run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/command_line.rb:27:in `map'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/command_line.rb:27:in `block in run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/reporter.rb:12:in `report'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/command_line.rb:24:in `run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/runner.rb:55:in `run_in_process'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/runner.rb:46:in `run'
>>>>>>      # 
>>>>>> /Users/siegfried/.rvm/gems/ruby-1.9.2-p136/gems/rspec-core-2.4.0/lib/rspec/
>>>>>>  core/runner.rb:10:in `block in autorun'
>> 
>>>>>> On Jan 11, 2011, at 7:05 AM, RipTheJacker wrote:
>> 
>>>>>>> You should probably just change that spec. The element that you want
>>>>>>> to test is a proc (you hope) getting invoked inside of the subject
>>>>>>> block, which is a weird pattern, and you don't need the #let blocks
>>>>>>> really, since you only use those objects once.
>> 
>>>>>>> Try:
>> 
>>>>>>> describe "#count!" do
>>>>>>>    specify "when a loan exists from giver to receiver" do
>>>>>>>        loan = Loan.gen
>>>>>>>        money_flow = MoneyFlow.gen(:giver => loan.loaner, :receiver =>
>>>>>>> loan.loanee, :currency => loan.currency)
>>>>>>>      expect do
>>>>>>>        Loan.count!(money_flow)
>>>>>>>      end.to_not change(Loan, :count)
>>>>>>>    end
>>>>>>>  end
>> 
>>>>>>> I'm assuming you are using rspec 2, though it will work in rspec 1.x
>>>>>>> with a syntax change. If you still get that error, post the new
>>>>>>> backtrace here. At the very least the spec and the backtrace will be
>>>>>>> more meaningful this way, and may be easier to debug (I hope).
>> 
>>>>>>> On Jan 10, 10:42 am, Zhi-Qiang Lei <[email protected]> wrote:
>>>>>>>> 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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>> 
>>>>>>>>> --
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>> 
>>>>>>>> Best regards,
>>>>>>>> Zhi-Qiang Lei
>>>>>>>> [email protected]
>> 
>>>>>>> --
>>>>>>> You received this
>> 
>> ...
>> 
>> read more ยป
> 
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Best regards,
Zhi-Qiang Lei
[email protected]

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