A simple implementation of the name property of our client model would be to add it as a QString; however, this approach has some shortcomings. Whenever we display this property in the UI, we will probably want to display an informative label next to the textbox so that the user knows what it is for, saying “Name” or something similar. Whenever we want to validate a name entered by the user, we have to manage that in the code somewhere else. Finally, if we want to serialize the value to or from JSON, again there needs to be some other component that does it for us.
To solve all of these problems we will introduce the concept of a DataDecorator, which will lift a given base data type and give us a label, validation capabilities, and JSON serialization out of the box. Our models will maintain a collection of DataDecorators, allowing them to validate...