Understand and Extend
Understand and extend modelsbuilder
Models are generated as partial classes. In its most basic form, a model for content type TextPage
ends up in a TextPage.generated.cs
file and looks like:
What is important is the Header
property. The rest is (a) a constructor and (b) some static helpers to get the PublishedContentType
and the PublishedPropertyType
objects:
Composition and Inheritance
Content type composition consists in having content types "inherit" properties from other content types. Contrary to C#, where a class can only inherit from one other class, Umbraco content types can be composed of several other content types.
The TextPage
content type could be composed of the MetaInfo
content type (and thus inherit properties Author
and Keywords
) and of the PageInfo
content type (and thus inherit properties Title
and MainImage
).
Each content type that is involved in a composition is generated both as a class and as an interface, and so the MetaInfo
content type would be generated as (some code has been removed and altered for simplicity's sake):
And the TextPage
model would be generated as (some code has been removed and altered for simplicity's sake):
A content type parent is a tree-related concept: In the Umbraco backoffice, a content type appears underneath its parent, if any. By convention, a content type is always composed of its parent and therefore inherits its properties. However, the parent content type is treated differently, and the child content type directly inherits (as in C# inheritance) from the parent class.
Therefore, assuming that the AboutPage
content type is a direct child of TextPage
, it would be generated as:
Extending
Because a model is generated as a partial class, it is possible to extend it. That could be by adding a property, by dropping the following code in a TextPage.cs
file:
Models builder does not take a custom partial class into account when generating the models. This means that if a custom partial class, inherits from a base class, tries to provide a constructor with the same signature, or implements a generated property, it will cause compilation errors.
Furthermore a generated model will always be instantiated with its default constructor, so if an overloading constructor is created it will never be used.
For more complex partial classes, you'll have to use the full version of the Models Builder.
Best Practices
Extending models should be used to add stateless, local features to models, and not to transform content models into view models or manage trees of content.
Example of good practice
A customer has "posts" that has two "release date" properties. One is a true date picker property and is used to specify an actual date and to order the posts. The other is a string that is used to specify dates such as "Summer 2015" or "Q1 2016". Alongside the title of the post, the customer wants to display the text date, if present, else the actual date. If none of those are present, the Umbraco update date should be used. Keep in mind that each view can contain code to deal with the situation, but it is much more efficient to extend the Post
model:
And to simplify the view as:
Example of bad practice
Because, by default, the content object is passed to views, one can be tempted to add view-related properties to the model. Some properties that do not belong to a content model would be:
A
HomePage
property that would walk up the tree and return the "home page" content itemA
Menu
property that would list the content items to display in a top menuEtc.
Generally speaking, anything that is tied to the current request, or that depends on more than the modeled content, is a bad idea. There are much cleaner solutions, such as using true view model classes that would be populated by a true controller and look like:
One can also extend Umbraco's views to provide a special view helper that would give access to important elements of the website, so that views could contain code such as:
Example of ugly practice
The scope and life-cycle of a model is not specified. In other words, you don't know whether the model exists only for you and for the context of the current request, or if it is cached by Umbraco and shared by all requests.
As a consequence, the following code has a major issue: the TextPage
model "caches" an instance of the HomePageDocument
model that will never be updated if the home page is re-published.
As a rule of thumb, models should never, ever reference and cache other models.
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