Code frameworks
Recipe: a derived stat
Calculate a value from other values with a ledger function.
Goal
Show a Ward that is half of the maximum HP, rounded down.
The change
Declare the function in the schema.
schemas/keeper.json
"ledgerFunctions": [
{
"id": "ward",
"name": "Ward",
"field": "ward",
"source": "rules/ward.ts"
}
]- Lines 19-22 field is the stored value Ward fills.
rules/ward.ts
export function ward(currentValue: number, self: ElementRef): number {
const max_hp: number = element.var(self, "max_hp") as number;
return math.floor(max_hp / 2);
}- Line 1 currentValue is the value so far. Most derived values ignore it.
- Line 2 Read what you need with element.var.
- Line 3 Return the derived number.
The constructor still returns the field, with a starting value of 0.
rules/keeper.ts
export function construct(
name: string,
max_hp: number,
): { name: string; max_hp: number; hp: number; ward: number } {
return { name: name, max_hp: max_hp, hp: max_hp, ward: 0 };
}- Lines 4-5 ward is returned as 0. The ledger function derives it right after.
Test it
scenarios/new-keeper.json
"ledger": [{ "function": "ward", "currentValue": 0, "expected": 5 }]- Line 6 Checks the function: it starts from 0 and must return 5.
Also add ward to expectedValues in every scenario for the Keeper.