Partial Classes allow a single class (or struct) to be declared spanning multiple source files by having each part amended with the
__partial keyword. All parts must be declared with the same visibility level. All parts must either declare the exact same set of ancestors, or only one part may declare any ancestors at all.
There is not much use for partial class syntax in regular user code, as Swift
extensions can perform all the same functionality (and are, in fact, treated identical to partial classes when defined within same project), but the
__partial syntax is provided for use in code generators such as .NET , which sometimes use code patterns that do not match well with the