30.2 Hierarchies and Disclosure in SwiftUI Lists

The previous chapter demonstrated the use of the List component to display so called “flat”, non-hierarchical data to the user. In fact, the List component can also present hierarchically structured data. It does this by traversing the data to identify the child elements in a data structure, and then presenting the resulting hierarchy visually. Figure 30-2 for example, shows the hierarchical data illustrated in Figure 30-1 above presented within a List view:

Figure 30-2

Clearly, this provides a better way to present the data to the user without having to traverse multiple depths of list navigation. Note also that disclosure controls are provided in the list to hide and show individual branches of data. Figure 30-3, for example, shows how the disclosure controls (highlighted) have been used to collapse the Toyota, Volvo and electric car data branches:

Figure 30-3

Clicking on a collapsed disclosure control...