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]"}