The SitePoint PHP blog has posted another in its series looking at Drupal 8 functionality today. In this latest post author Daniel Sipos looks at entity validation and typed data and what functionality the project provides over what was offered in previous versions (built on top of the Symfony validation component).

Data validation is a very important part of any application. Drupal 7 has a great Form API that can handle complex validation of submitted data, which can then be turned into entities. However, form level validation is problematic. [...] With the introduction of subsystems such as the REST API, Drupal 8 needed something better to handle this problem. [...] In this article, and its followup, we will explore the Drupal 8 Entity Validation API, see how it works, and how it can be extended.

He starts by looking at typed data and the consistency it provides in working with the metadata on objects. He includes a few examples of defining a string data type with a maximum length. He then applies this to content entities and enforcing the constraints provided by the types. In the next part of this series he'll look at the validation itself and how it works with these types/constraints.