按钮没有显示在用MarkupKit编写的简单应用程序上，只有一个按钮

I'm a totally blind developer trying to learn Swift and iOS programming. Since interface builder is not accessible in the latest xcode I'm trying to use MarkupKit to create a UI. I'm attempting to create a simple app with one button which displays an alert. While the view with proper title displays the button does not. Based on the sample I believe I need to set the value of the button to self but am not sure how to do this. Contents of my view.xml isI'm a totally blind developer trying to learn S