Your thoughts on why to just expose it out as an ienumerable make sense.
There's positives and negatives to both. Wrapping it in a ReadOnlyCollection
initializes it, as well as prevents you from ever being able to take
advantage of lazy=extra.
On Mon, Feb 1, 2010 at 6:37 PM, Paul Batum <paul.ba...@gmail.com> wrote:
> Yes, sorry, there was an error in my code. You can map the member as
> either a field or a property, but you have to use the appropriate
> access mechanism. ReadOnlyPropertyThroughCamelCaseField tells
> NHibernate to use the mapped property when getting the value, and to
> look for a field with camel case naming and to use that when setting
> the value. If the underlying member is an autoproperty, then it will
> fail to find a matching field.
>
>
> On Tue, Feb 2, 2010 at 8:17 AM, TheNephalim <robert.eberh...@gmail.com>
> wrote:
> >
> > I implemented what Paul suggested, although I had to do it slightly
> > differently and I'm not sure why.
> >
> > public class User {
> >
> > private IList<Phone> _phones;
> >
> > /// <summary>
> > /// A list of contact phone numbers.
> > /// </summary>
> > public virtual IEnumerable<Phone> Phones {
> > get { return _phones; }
> > }
> >
> > public virtual void AddPhone(Phone phone) {
> > Check.Require(phone != null, "Phone cannot be left
> > undefined.");
> >
> > if (!_phones.Contains(phone)) {
> > _phones.Add(phone);
> > }
> > }
> > }
> >
> > The mapping for the property is:
> >
> > HasMany<Phone>(x => x.Phones)
> > .Access.ReadOnlyPropertyThroughCamelCaseField
> > (Prefix.Underscore)
> > .Table("Phone")
> > .KeyColumn("UserId")
> > .Cascade.All().Inverse()
> > .AsBag();
> >
> > If I added the get/set to the private IList<Phone> _phones, I received
> > an error indicating that it couldn't find the field "_phones".
> > However, now that I'm thinking about it, that might make sense because
> > having the get/set would indicate a propert and not a field. I'm not
> > sure if the the Property access strategy would work and I believe that
> > you would also have to use the Reveal.Property<Entity>("Property")
> > method. I also think that you would probably have to rename the
> > property to something like m_Phones. I have not have too much luck
> > using the Reveal.Property method; sometimes it seems to work and other
> > times....not.
> >
> > I also had to change the List<T> to IList<T>, otherwise to access
> > contains I would have to access it through the public IEnumerable
> > Phones instead of the private variable. To add a new value, I would
> > need to access the private variable, but would receive an error
> > indicating an index out of range exception. Changing the collection
> > from List<T> to IList<T> seems to have remedied that problem.
> >
> > I'm going to continue testing to make sure that everything is cool.
> > It appears, though, that I have reached something that I can
> > definitely live with.
> >
> > Thanks again,
> > Robert
> >
> > On Jan 30, 6:53 pm, Paul Batum <paul.ba...@gmail.com> wrote:
> > > I'm familiar with what AsReadOnly does - it used to be my preferred
> > > approach! Until I realised that compile time errors are preferable to
> > > runtime errors :)
> > >
> > > You could argue that a combination of both techniques is best - that
> way
> > > you're still exposing a readonly interface and preventing the casting
> > > problem. But if my developers are casting back to lists instead of
> using the
> > > appropriate methods (AddXXX, RemoveXXX), I've got bigger problems. I
> try to
> > > expose a public interface that makes the wrong things hard and the
> right
> > > things easy - I rarely go further than that. YMMV.
> > >
> > > On Sun, Jan 31, 2010 at 2:27 AM, Hudson Akridge <
> hudson.akri...@gmail.com>wrote:
> > >
> > > > You can make the getter an IEnumerable for your property wrapper, but
> you
> > > > can still cast it back to a list and then make modifications to it.
> > > > .AsReadOnly() wraps it in a new read only collection that throws
> exceptions
> > > > whenever .Add/.Remove or any other collection modification methods
> are
> > > > attempted to be called. Otherwise all you're doing it providing a
> read only
> > > > interface, but not actually enforcing it.
> > >
> > > > Example:
> > > > public class Person
> > > > {
> > > > public Person()
> > > > {
> > > > _test = new List<string>();
> > > > }
> > > > private readonly IList<string> _test;
> > > > public IEnumerable<string> Test
> > > > {
> > > > get { return _test; }
> > > > }
> > > > }
> > >
> > > > //Usage
> > > > var tmp = new Person();
> > > > var tmp2 = tmp.Test as List<string>;
> > > > tmp2.Add("test");
> > >
> > > > tmp2 will have a count of 1 after this, and "test" will have been
> added.
> > > > This is typically not what you'd want a user of your model to be able
> to do.
> > >
> > > > On Fri, Jan 29, 2010 at 11:23 PM, Paul Batum <paul.ba...@gmail.com>
> wrote:
> > >
> > > >> Not sure if I'm following entirely, but my approach to exposing
> > > >> collections is to make the getter an IEnumerable:
> > >
> > > >> public class Foo
> > > >> {
> > > >> private List<Bar> _bars { get; set; }
> > >
> > > >> public IEnumerable<Bar> Bars
> > > >> {
> > > >> get { return _bars; }
> > > >> }
> > > >> }
> > >
> > > >> Then I map this using an access strategy:
> > >
> > > >> public void Override(AutoMapping<Foo> mapping)
> > > >> {
> > > >> mapping.HasMany(x => x.Bars)
> > >
> > > >> .Access.ReadOnlyPropertyThroughCamelCaseField(Prefix.Underscore)
> > > >> }
> > >
> > > >> On Sat, Jan 30, 2010 at 4:20 AM, TheNephalim <
> robert.eberh...@gmail.com>wrote:
> > >
> > > >>> I'm definitely going to look into the other strategies that you
> > > >>> mentioned.
> > >
> > > >>> One that I found, and seems to work, is the wrapper strategy that
> you
> > > >>> alluded to in item number 4. I created a private property that is
> > > >>> revealed in the mapping and is accessed using the wrapper in a
> public
> > > >>> property. When I tested two other properties that I had
> implemented
> > > >>> in this fashion, NHibernate determined that the collections were
> not
> > > >>> initialized using the assert that I mentioned in my previous
> posting
> > > >>> and only generated SQL if I directly accessed the collection
> directly,
> > > >>> i.e. User.Phones.Count.
> > >
> > > >>> Thank you for your response and confirming what I was thinking as
> well
> > > >>> as giving me some other avenues to pursue.
> > >
> > > >>> -Robert Eberhart
> > >
> > > >>> On Jan 29, 11:54 am, Hudson Akridge <hudson.akri...@gmail.com>
> wrote:
> > > >>> > You may want to toss your question over to the NHUsers google
> group,
> > > >>> but
> > > >>> > I'll give you my feedback for as much as It'll help ;)
> > >
> > > >>> > is this a trade off wherein we sacrifice encapsulation for
> performance
> > >
> > > >>> > This. As far as I'm able to gleen, that is the correct assumption
> to
> > > >>> make.
> > > >>> > There are ways around this.
> > > >>> > 1.) Don't access the collection unless you absolutely need it
> > > >>> > 2.) Look into doing Join Fetch's during your queries when you get
> the
> > > >>> data
> > > >>> > back if you know you're going to be using that collection as a
> result
> > > >>> of the
> > > >>> > query.
> > > >>> > 3.) Look into batch or subselect fetching, this is a good loading
> > > >>> strategy
> > > >>> > imo
> > > >>> > 4.) Look into lazy=extra. This allows you to do counts, contains,
> and a
> > > >>> few
> > > >>> > other common collection statements without loading the
> collection. You
> > > >>> will
> > > >>> > still have to access the backing collection, but you can write a
> > > >>> wrapper in
> > > >>> > your model. For example:
> > > >>> > public virtual int FastCountOfLogins()
> > > >>> > {
> > > >>> > return _logins.Count();
> > >
> > > >>> > }
> > >
> > > >>> > That will keep your collection lazy loaded until you actually
> need to
> > > >>> do
> > > >>> > something like a for each and iterate over it.
> > > >>> > 5.) Grab nhprofiler. This is one of the single best tools for
> finding
> > > >>> bottle
> > > >>> > necks in your application.
> > >
> > > >>> > On Fri, Jan 29, 2010 at 8:10 AM, TheNephalim <
> > > >>> robert.eberh...@gmail.com>wrote:
> > >
> > > >>> > > I have several issues that I'm working on, because I'm a newbie
> at
> > > >>> > > this, and wanted to address the one that I "solved" first.
> > >
> > > >>> > > The problem was that I was noticing that all of my collections
> were
> > > >>> > > not loading lazily, no matter what I did to mark them as such.
> It
> > > >>> > > then dawned on me that the problem was the way I was returning
> the
> > > >>> > > collection.
> > >
> > > >>> > > For example,
> > >
> > > >>> > > public virtual IList<Login> Logins {
> > > >>> > > get { return new List<Login>(_logins).AsReadOnly();
> }
> > > >>> > > protected set { _logins = value; }
> > > >>> > > }
> > >
> > > >>> > > I did it this way because if you just return _logins, you're
> actually
> > > >>> > > returning a reference to the private variable which violates
> > > >>> > > encapsulation and the whole reason for marking it private in
> the
> > > >>> first
> > > >>> > > place.
> > >
> > > >>> > > The problem is that the parent object, User, is a proxy. Any
> time
> > > >>> > > that that parent object was accessed, for example, to set
> > > >>> > > User.LastName, a query for each of the collections was fired.
> The
> > > >>> > > solution was to change the property to this:
> > >
> > > >>> > > public virtual IList<Login> Logins {
> > > >>> > > get { return _logins; }
> > > >>> > > protected set { _logins = value; }
> > > >>> > > }
> > >
> > > >>> > > I have run several tests in NUnit and watched the queries
> coming back
> > > >>> > > to know that this is what's happening. Additionally, I used
> the
> > > >>> > > following:
> > >
> > > >>> > >
> Assert.IsFalse(NHibernateUtil.IsInitialized(testUser.Logins));
> > >
> > > >>> > > It passes for the second property implementation and not the
> first.
> > >
> > > >>> > > The question I have is this: Is there a way to encapsulate the
> > > >>> > > private variable but still have a proxy for lazy loading, or is
> this
> > > >>> a
> > > >>> > > trade off wherein we sacrifice encapsulation for performance?
> > >
> > > >>> > > Any help you can offer is appreciated.
> > >
> > > >>> > > Sincerely,
> > > >>> > > Robert Eberhart
> > >
> > > >>> > > --
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> > >
> > > >>> > --
> > > >>> > - Hudsonhttp://www.bestguesstheory.comhttp://
> twitter.com/HudsonAkridge
> > >
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