In the book .NET Domain-Driven Design with C# from Tim McCarthy there's an example of a link table (two foreign keys + one boolean column) that gets it's own class in the domain. Is this common?
The example is a Contact table and a Project table. The link table is a ProjectContact. What are the pros and cons of using a class ProjectContact instead of having a List of Contacts property in the Project class and a List of Projects property in the Contact class?
I must say that having a ProjectContact class makes it easy to persist a new link between a Project and a Contact... but it seems overkill to me.
Pragmatically spoken (I'm not a DDD expert), I would say that a link table shouldn't pop up in the domain unless it is an entity on it's own (i.e. you need to attach behaviour to it, or it has properties other than the foreign keys).
Related
I have sample project for identity customization using
Install-Package Microsoft.AspNet.Identity.Samples -pre
command. But, for this project I have a general ApplicationUser class representing all the users of my application. What if I have different categories of users. For example, I may have Teacher and Student entities and data representing both the entities will be different. How can I customize my application to store data for both the entities having all the features of ApplicationUser?
One way that I think is inheriting both the classes from ApplicationUser and then doing appropriate changes in IdentityConfig.csand defining Controllers for each of them. Is there any other efficient way of doing this?
What if I want to use the built-in authentication and authorization features but using database first workflow?
First, you want to know how to create "types" of users. The way you would do that is exactly how you expected: inherit from ApplicationUser. By default, this will result in a single "users" table with an additional Discriminator column. This column will store the class type that was persisted, i.e. "Teacher", "Student", or "ApplicationUser", and EF will utilize this information to new up the right class for each particular record.
One thing to note with this, though, is that you need to be aware of how UserManager works, namely that it's a generic class (UserManager<TUser>). The default AccountController implementation you have from the sample defines a UserManager property on the controller which is an instance of UserManager<ApplicationUser>. If you use this instance with something like Teacher, it will be upcast to ApplicationUser. In particular if you were to do something like UserManager.Create(teacher), it will actually save an ApplicationUser, instead (the Discriminator column's value will be "ApplicationUser", rather than "Teacher"). If you need to work with the derived user types, you'll need to create separate instances of UserManager<Teacher> and UserManager<Student> for that purpose.
Next, you want to know if you can use a "database first workflow". To answer that, we need to define exactly what that means. EF has what it calls "Database First" which employs EDMX to represent your database entities. This in particular is incompatible with Identity. However, despite the name, what EF calls "Code First", can work with an existing database just as well as create a new one. In other words, yes, you can use an existing database, if you prefer, but no you cannot use "Database First", in the EF-sense. For more information about using an existing database with Code First, see my post.
I have some points on a map with associated informations contained by Core Data, to link the points on the map with the associated info, I would like to have an ID for each point, so in my entity, I would need some ID property, I have read that Core Data has it's own IDs for every managed object but I'm wondering wether or not it would be a good approach for me to directly use them or if I should create my own ID system ?
If you think I should create my OWN ID system, how would I do that ?
Thank you.
CoreData is not an relational database and you should avoid thinking about own ID’s. You may need them only for syncing purposes with external databases. For more precise answer, you should write how your model looks.
[edited after comment]
I don't see that you need any relations. Let's sat you have MapPoint entity with lat, and long properties. If there is only one user note, you just add another property to it like notes. If you have many informations (many records) stored with one MapPoint you need to add Notes entity with properties note and mappoint and make a relation between them. When you insert new Notes object into CoreData you set mappoint property to already existing MapPoint object (fetched after user tap).
I am coding an MVC internet application, and I have a question in regards to using the ViewBag.
In many of my controllers, I have SelectList objects, where the user can select an object. The object that is selected is a foreign key value for my model.
My question is this: Should I use ViewBag for this? How secure is the ViewBag? Should I use values in my ViewModel instead of the ViewBag?
Thanks in advance.
Use your view model.
When the ViewBag was implemented (MVC 3) dynamic typing was new (.NET 4.0) and it was put in just as a side-option to ViewData or to quickly generate a view without the need for additional classes.
Any serious MVC project will take advantage of a model/viewmodel with a strongly typed view.
There are no security concerns with either because both essentially only exist through the controllers lifespan.
There are no security concerns with ViewBag since it is disposed once rendered in the View.
I think the answer really should be "it depends". For example, if you have 6 collections required to populate dropdown lists aand you want to get the data posted back, you should definitely use a ViewModel for this. Since 6 collections will be hard to manage if they are stuffed in ViewBag with no strong typing in the view, especially if another developer comes along later needing to do maintenance to the view.
Generically everything should be done inside a view model. That's what a view model is. A class that you specifically define to meet the requirements of your view. Here is an image depecting when to Use TempData, ViewBag or ViewData
It's easier to generate tables and default classes with liferay's service builder.
But it is bit difficult for me to understand the hierarchy of classes generated by it.
Also the exact use of each class other than modifying LocalServiceImpl class as per our need by adding our own functionality.
I have gone through Service Builder doc. So I got some basic knowledge but would like to get more on this.
Even the link "Liferay Service Builder" was useful but outdated with current Liferay version. So Does anyone have update on above link or nice info explaining hierarchy with example/diagram?.
Any help is appreciated.
Thanks.
To implement the foreign key concept in liferay, you have to apply your own coding logic since the implementation of FK are not available in service builder. So I guess you need to put some code.
Read some forums related to service builder on liferay website. It will give you better exposure.
Read Liferay In Action. It is a good book
Here is What I obeserved In Liferay 6.1.
com.liferay.portlet.p_name.model:
This has interfaces and classes related to (table entity related to) this portlet.
For example com.liferay.portlet.announcements.model will have
Interfaces:
AnnouncementsEntry
AnnouncementsEntryModel
AnnouncementsDelivery
AnnouncementsDeliveryModel
AnnouncementsFlag
AnnouncementsFlagModel
Classes:
And In classes section, You will find wrapper classes and soap classes for each entity like:
AnnouncementEntryWrapper
AnnouncementEntrySoap
AnnouncementFlagWrapper
AnnouncementFlagSoap
AnnouncementDeliveryWrapper
AnnouncementDeliverySoap
Also for few Entity, you will find Classes for Constant entries like
AnnouncementsEntryConstants, AnnouncementsFlagConstants etc.
com.liferay.portlet.p_name.service:
This has classes and interfaces related to (table entity related to) this portlet.
For example com.liferay.portlet.announcements.service will have
Interfaces:
AnnouncementsEntryService
AnnouncementsEntryLocalService
AnnouncementsDeliveryService
AnnouncementsDeliveryLocalService
AnnouncementsFlagService
AnnouncementsFlagLocalService
Classes:
And In classes section you will have Util and Wrapper classes.
AnnouncementsEntryServiceUtil
AnnouncementsEntryServiceWrapper
AnnouncementsEntryLocalServiceUtil
AnnouncementsEntryLocalServiceWrapper
and so on.....
So In short following is the structure I observed in Liferay
[In Model, I:+Model,(ModelName), C:Soap, Wrapper and Constants]
[In Service, I:Service,LocalService ; C:ServiceUtil,ServiceWrapper,LocalServiceUtil and LocalServiceWrapper]
[In Persistence, I:Finder(BlogsEntryFinder),Persistence(BlogsEntryPersistence); C:Util(BlogsEntryUtil, BlogsEntryFinderUtil)]
Note:
I --> Interface
C --> Class
I have a working Core Data app and I want to display a representation for some of the Entities. I have set up an NSCollectionView with the Interface Builder "Core Data Entity Assistant" to setup the collection (generated a View in the MyDocument.xib), and can access simple representedObject.attributes, as well as simple relationship attributes.
my problem is with the to-many Relationships, which I would like to display as tables nested in the Collection item. I have tried different representedObject keypath combinations for the NSTableColumns, but did not figure out the correct cocoa binding incantation to drill down the data.
EntityA (reprensented in the Collection) <WORKS>
. EntityB (simple relationship) <WORKS with representedObject.relationship.attr>
.. EntityC (to-many-relationsip of EntityB) <how to get there???>
as of right now 99% of the code is generated through the Core Data Model and by Interface Builder. I am not opposed to subclassing something to get the desired behavior but I would prefer to keep things as automated as possible -- especially since this should "just work" with the as-is classes. using Xcode 3.2.5 -- I don't mind jumping to 4GM if someone tells me the bindings are more explicit there.