Where to Put Common Code Found in Multiple Models

Where to put common code found in multiple models?

Create a module, which you can put in the lib directory:

module Foo
  def foo
    # do something
  end
end

You can then include the module in each of your model classes:

class A < ActiveRecord::Base
  include Foo
end

class B < ActiveRecord::Base
  include Foo
end

The A and B models will now have a foo method defined.

If you follow Rails naming conventions with the name of the module and the name of the file (e.g. Foo in foo.rb and FooBar in foo_bar.rb), then Rails will automatically load the file for you. Otherwise, you will need to use require_dependency 'file_name' to load your lib file.

Is there a recommended way to use models and common files in multiple flutter projects?

The conventional approach would be put your common code in a separate Dart package (that is, a separate directory with its own pubspec.yaml file and its source files in a lib subdirectory). Unless you want your package to be public, there is no need to publish your package to pub.dev.

Your other projects can then add that package as a dependency in their pubspec.yaml files. For packages not hosted on pub.dev, you probably will want to specify a local filesystem path to the package or to specify an URL to your own Git server. See the Package Dependencies documentation for more details.

Other approaches (that I don't recommend, but I mention for completeness):

• Have your projects just import common .dart files by relative paths. However, navigating up multiple parent directories is very ugly.
• In your projects' source directories, add symlinks that refer to the common code. Then you could import common files by relative path without needing to navigate up parent directories.
• If you use separate source control repositories instead of a mono-repo, you could make each project consume common code as a Git submodule. Unlike the two approaches above, this would allow your different projects to use independent versions (the flipside is that that flexibility would be more work to maintain).

Correct way to make function available in multiple models

1. Use polymorphism if this models have multiple realizations of this method. However, if method universal for models, choose second.

   class Product extends AbstractThumbnailedModel
   {
       public function setThumbnailAttribute(Thumbnail $thumb)
       {
           // implement setter for Product
       }
   } 
   
   class AnotherProduct extends AbstractThumbnailedModel
   {
       public function setThumbnailAttribute(Thumbnail $thumb)
       {
           // implement setter for AnotherProduct
       }
   } 
   
   abstract class AbstractThumbnailModel extends Model 
   {
       abstract public function setThumbnailAttribute(Thumbnail $thumb);
   }
   

2. Use traits. Create trait Thumbnailed and use it when needed in models.

   trait Thumbnailed 
   {
        public function setThumbnailedAttribute(Thumbnail $thumb)
        {
            // here implementaition which will share with needed models
        }
   }
   
   class Product extends Model
   {
       use Thumbnailed;
       // Use it!
   } 
   
   class AnotherProduct extends Model
   {
       use Thumbnailed;
       // same method implementation. Just use it!
   
   } 
   

P.S. Sorry for Google translate

Where to put custom callbacks that I use in several models

Marek's answer is good but the Rails way is:

module NormalizeDateModule
  extend ActiveSupport::Concern

  included do
    after_validation :normalize_date
  end

  def normalize_date
    self.created_at = return_DateTime(created_at)
  end
end

Doc here.

(and you have a decicated folder for it: models/concerns)

Flutter Scoped Model - Passing multiple Models

That is one way you can do it. I use Mixins to compile different beahviours / features into the AppModel. Each model is responsible for a section/feature in the application. As an example I have a UserModel, SettingsModel and ContentModel

They are all mixins on the Model class from the ScopedModel library

mixin UserModel on Model {
 ...
}
mixin SettingsModel on Model {
 ...
}
mixin ContentModel on Model {
 ...
}

And then my main AppModel looks like this

class AppModel extends Model with UserModel, SettingsModel, ContentModel {
  ...
}

This way I'm combining behaviours from different models, if you want to only expose the one type of model you can cast it and use that interface.

I'm curently leaning towards this way where the Model files manages all the state for certain features and in those models I inject services which are singleton instance to share information between them if needed. These services perform all my actual business logic, Connecting to the API, serializing and compiling into contextual information for my app.

Comments on multiple models

You don't want to specify each type of object that can hold Comment objects. That creates a headache of if-elsif-else blocks all over the place. Instead, you want things to be Commentable, and they all will have .comments on them.

This is called a polymorphic association in Active Record. So you would have your models something like:

class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
end

class Post < ActiveRecord::Base
  has_many :comments, as: :commentable
end

class Book < ActiveRecord::Base
  has_many :comments, as: :commentable
end

And modify your database accordingly, it's all in the linked article. Now when you build a Comment object for a form, it will have pre-populated a commentable_id and commentable_type, which you can toss in hidden fields. Now it doesn't matter what the Comment is associated with, you always treat it the same.

I'd leave User as a separate association, since it's not really the same idea.

Entity Framework 6 Code First - Multiple Model/Configurations

I have been able to solve my own question now having found a new article to refer to Multiple Model EF 6 Data points

Read the article on how to solve my question and other variants of similar problems. The key to solving this problem was to specify separate folders for each context migration when commanding the NuGet Package Manager Console. Then in the initialiser for each context, refer to the configuration in the appropriate migration folder. Rather than repeating here, please see the article on MSDN I linked to as all the information I needed was in there, plus lots more.

Multiple Models in a Single View (C# MVC3)

You should always create separate ViewModels for your views. There should be an abstraction from your Views to your Domain Models. In the demos/tutorials they show it all pretty and easy by simply strongly typing the Views to Domain Models but that's not a good strategy. The views should not be dependent on the business objects.

You should implement David Glenn's proposed solution for your current scenario and also for all other views even if requires mapping the domain model to to another view model class.

EDIT:

If you have lets say a top Menu > TopMenu.aspx
And you have multiple partial views inside it > StudentMenu.ascx, ResultMenu.ascx

You will create a View Model for Top Menu > TopMenuViewModel.cs
And you will also create view models for partial views > StudentMenuViewModel , ResultMenuViewModel etc.

and your TopMenuViewModel will have both >

class TopMenuViewModel 
{
   //all the stuff required in TopMenu.aspx
   StudentMenuViewModel studentvm;
   ResultMenuViewModel resultvm;
}

and in TopMenu.aspx when rendering the partial you will pass the relevant view model >

Html.RenderPartial('StudentView', Model.studentvm)

Hope it makes sense

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