formula
formula ( formulaExp : expression ) : 4D.Function
| Parameter | Type | Description | |
|---|---|---|---|
| formulaExp | expression | → | formula to be returned as object |
| Result | 4D.Function | ← | Native function encapsulating the formula |
Description
The formula command creates a 4D Function object based upon the formulaExp expression. formulaExp expression can be as simple as a single value or complex, such as a project method with parameters.
The returned formula can be called with:
.call()or.apply()functions, or- object notation syntax (see formula objects).
var f : 4D.Function
f = formula(1+2)
o = newObject("myFormula",f)
//three different ways to call the formula
f.call(o) //returns 3
f.apply(o) //returns 3
o.myFormula() //returns 3
You can pass parameters to the formula, as seen below in example 4.
You can specify the object on which the formula is executed, as seen in example 5. The properties of the object can then be accessed via this.
If formulaExp uses variables, their values are copied and stored in the returned formula object when it is created. When executed, the formula uses these copied values rather than the current value of the variables.
The object created by formula can be saved, for example, in a datastore attribute or in a blob document.
Example 1
A simple formula:
var f : 4D.Function
f = formula(1+2)
var o : object
o = newObject("f",f)
result = o.f() // returns 3
Example 2
A formula using variables:
var value : integer
value = 10
o = newObject("f",formula(value))
value = 20
result = o.f() // returns 10
Example 3
A simple formula using parameters:
o = newObject("f",formula($1+$2))
result = o.f(10,20) //returns 30
Example 4
A formula using a method with parameters:
o = newObject("f",formula(myMethod))
result = o.f("param1","param2") // equivalent to result = myMethod("param1","param2")
Example 5
Using this:
o = newObject("fullName",formula(this.firstName+" "+this.lastName))
o.firstName = "John"
o.lastName = "Smith"
result = o.fullName() //returns "John Smith"
Example 6
Calling a formula using object notation:
var feta, robot : object
var calc : 4D.Function
robot = newObject("name","Robot","price",543,"quantity",2)
feta = newObject("name","Feta","price",12.5,"quantity",5)
calc = formula(this.total = this.price*this.quantity)
//sets the formula to object properties
feta.calc = calc
robot.calc = calc
//call the formula
feta.calc() // feta = {name:Feta,price:12.5,quantity:5,total:62.5,calc:"[object formula]"}
robot.calc() // robot = {name:Robot,price:543,quantity:2,total:1086,calc:"[object formula]"}