Calculation
- Version
- 4.0 preview
- Updated
A reference to a calculation, picked from the calculations of the relevant product.
Storage kind: column · Column: int unsigned, nullable by default
Use it for any field that points at a calculation — an answer's price calculation, a question's
maximum-value calculation, a shipping rule's cost. It extends join, so it is a join
with the extras this one case needs: a "no calculation" placeholder, product grouping, a link
through to the referenced calculation, and copy semantics that follow the calculation.
Settings
| Setting | Meaning |
|---|---|
modelClass / modelMethod | Where the pickable calculations come from |
propNameKey / propNameDisplay | Key and label fields, as for a join |
defaultlabel | Placeholder — conventionally "No Calculation" |
groupby | Group the options, typically by product |
dropdownOrdering | Order of the option list |
showLinks | Render a link through to the referenced calculation |
isPseudoJoin | Suppress the SQL join |
It inherits everything else join accepts.
Nullable by default
"No calculation assigned" is the normal state for most fields carrying one, so this type declares
getDefaultNullable() as true — the only type besides datetime that defaults
nullable.
Several of these columns also have ON DELETE SET NULL foreign keys — answers.calcmodel,
questions.calcmodel_id_max_val — which makes NOT NULL impossible regardless of preference: the
database will write NULL into them when a calculation is deleted. Treat NULL as the normal absent
value and read it as "no calculation", never as an error.
Copying follows the calculation
copyCalculation() runs during a record copy, so a copied record points at a copy of the
calculation rather than sharing the original. That is what keeps a duplicated product's pricing
independent — edit the copy's calculation and the original is untouched.
It is the same shape as rule's copyRule() and calculationOverride's copyOverrides(): a
reference that would otherwise alias shared state across a copy.
copyCalculation() honours storeExternally, writing the new reference to the foreign table when
the property lives there.
Notes
It behaves as a join for query building — it extends the join type — but exists separately because
a calculation reference is a distinct thing to pick, order and link to. showLinks in particular
only makes sense here: it renders a link from the referencing form straight into the calculation
editor, which is how an operator gets from "this answer is priced somehow" to the formula.
@see join.md @see calculationoverride.md — per-customer-group overrides of a reference like this @see ../com_configbox_calculation_engine.md @see ../../admin-guide/pricing/build-a-calculation.md — what the operator sees