When a save is refused

Ana saves Telling Time to the Half Hour with a long title, too many minutes, and the code TT-HOUR.

Each field has rules, and a save that breaks them is refused. The tools name every field rule it breaks at once, then check that the code is the lesson's own.

Try it: select each marked part, and read what Ana would be told.

Telling Time to the Half Hour, as Ana tried to save it

The lesson as a page

The fields it's made of

First, every field rule the save breaks

The title can be at most 60 characters; this one has 66.
A lesson can be at most 90 minutes; this one says 120.

Then, once those are fixed

TT-HOUR is already the code of Telling Time to the Hour. Every lesson needs a code of its own.

A tool that checks before saving

TT-HOUR is taken: Telling Time to the Hour has it.

Telling Time to the Half Hour, as Ana tried to save it. First, every field rule the save breaks: The title can be at most 60 characters; this one has 66. A lesson can be at most 90 minutes; this one says 120. Then, once those are fixed: TT-HOUR is already the code of Telling Time to the Hour. Every lesson needs a code of its own.

If you tried this

Loading Telling Time to the Half Hour

Ana fixes the title and the minutes, saves again, and only then hears that TT-HOUR is taken. A tool can check the code before saving, so Ana hears it all at once.