💡 Sept. Tip => cardinality leads to all directions

In libmodulor, the optionality and mandatoriness of a use case input field is defined via cardinality.

The default cardinality is { max: 1, min: 1 }. It means that the field is mandatory. Since it's the default value, we don't have to define it for each input field.

const CreateOperationUCD: UCDef<CreateOperationInput, CreateOperationOPI0> = {
    // ...
    io: {
        i: {
            fields: {
                // By default, title is mandatory
                title: {
                    type: new TFreeTextShort(),
                }
            }
        }
    }
    // ...
}

What if we want to add an optional field ? Like so :

// ...
description: {
    cardinality: {
        min: 0,
    },
    type: new TFreeTextLong(),
}
// ...

I see you from there telling yourself that it could be a boolean. Well. What if we want to add an optional field that can take at most 3 values ? Like so :

// ...
picture: {
    cardinality: {
        max: 3,
        min: 0,
    },
    type: new TFile({
        type: {
            allowed: ['image/jpeg', 'image/jpg', 'image/png'],
        },
    }),
},
// ...

And now, what if we want exactly 5 values ? Like so :

// ...
tag: {
    cardinality: {
        max: 3,
        min: 3,
    },
    type: new TSlug(),
},
// ...

As we can see, we can express basically anything with cardinality.

Voilà c'est tout.