Howto: optional type-in field in Anki

Anki is a program that lets you quiz yourself periodically. It models the so-called forgetting curve: by recalling some fact, you strengthen the memory of it. I use Anki to memorize English words and idioms, and I’m pretty sure I wouldn’t have been able to express myself this freely if I didn’t practice with the program.

To make Anki quiz you on something, you create a note with one or more fields. Anki turns notes into cards; during the quiz, it shows you the front side of the card and waits for you to recall the back. You then flip the card and check your answer. The appearance of each side can be controlled through templates and CSS styling.

Most of the time, it’s sufficient to have a single card with a “question” field on the front and an “answer” field on the back. But other times, it’s not enough. For example, some of my cards require me to type-in the answer, manually, e.g. to ensure that I memorized the spelling. I also got a number of notes that turn into different sets of cards depending on what flags I specify in the note.

Now here’s the problem: I have a deck (a collection of notes) with some random facts. For some of those, I’d like a simple question-answer card, but for others, I want to input the answer by hand. How do I do this?

Anki doesn’t generate cards with empty front side, so my first thought was:

1. create a new field named “Add a card with input field for Answer”;
2. create a new card template where the front side is generated only if the aforementioned field is non-empty;
3. in my existing question-answer card, change the template to only generate the front when the field is empty.

Steps two and three create mutually exclusive cards; Anki would generate one or the other, but not both. Unfortunately, the third step doesn’t work: as of Anki 2.1, the docs say that “negated expressions can not be used to control card generation”. I can make Anki generate a card when the field is non-empty, but I can’t prevent it from generating a card when the field is empty. Bummer.

After a bit more thinking, I realized that the same goal can be accomplished by changing the back side: it will show either the answer or an input field. The final tweak was to put the input field on the front of the card, because that’s how Anki wants it (and it does make sense). And that works!

Here’s the final template I used for the front:

{{Question}}

{{#Add a card with input for Answer}}
{{type:Answer}}
{{/Add a card with input for Answer}}

It always shows the question, but the input field is only shown when the note field “Add a card with input for Answer” is not empty.

The template for the back of the card looks like this:

{{FrontSide}}

{{^Add a card with input for Anwer}}
<hr id=answer>

{{Answer}}
{{/Add a card with input for Answer}}

It repeats the front side (which is handy because that’s where the question was), but only shows the answer if the “Add a card…” field was empty. Thus, I get one of two cards, depending on the value of that field: either a “question-answer” card, or a “question with a type-in field” card. Mission accomplished!