TablePrinter Example

Let’s look at another example in detail. The TablePrinter class provides a table printing service for other objects. It prints a single column table of strings with an optional title and optional line numbers. A TablePrinter can create a table for any object as long as the object conforms to the <TablePrinterDataSource> protocol. This is an attractive way to do business. The TablePrinter itself never stores any of the data used in the table. It doesn’t have to know what class the data source is or anything about it, only that the data source can answer certain questions (via a message) like “How many rows are in this table?” or “What information goes in row j?”