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openVALIDATION provides various functions. Let's say we want to check in a rule whether we have spent more money on shopping than our budget allows.
We have the following scheme:
- article : text
price : 0
article : "text",
price : 0
And here's the rule that goes with it:
SUM OF shopping_list.price
the expenses MUST NOT EXCEED the budget of 20 €.
First, we define a variable called Expenses. This variable uses the SUM OF function. The list of all prices from the shopping list is transferred to the function. The function SUM OF calculates a sum and thus has a return value of type Number. The Issues variable is automatically assigned this data type and can then be used within the rule.
The rule itself contains a numeric comparison operation. The whole thing looks like this:
var expenses = sum(shopping_list.map(a -> a.price))
If (expenses > 20 )
throw Error("the expenses MUST NOT EXCEED the budget of 20 €")
Functions can of course also be used within a rule.