Formula

4D.Formula objects are created by the Formula or Formula from string commands and allow you execute any 4D expression or code expressed as single-line text.

4D.Formula class objects inherit from the 4D.Function class. Thus, to execute the formula, you can:

• store a 4D.Formula object in an object property and use the () operator after the property name,
• or directly call the 4D.Formula object using the call() or apply() function on it.

See examples in the Executing code in Function objects paragraph.

Passing parameters to formulas

You can pass parameters to your formulas using a sequential parameter syntax based upon $1, $2,...,$n. The numbering of the $ parameters represents the order in which they will be passed to the formula. For example, you can write:

 $f:={message: Formula(ALERT("Hello "+$2+", "+$1))}
 $f.message("John";"Smith") //displays "Hello Smith, John"

Or using the .call() function:

 var $f : 4D.Formula
 $f:=Formula($1+" "+$2)
 $text:=$f.call(Null;"Hello";"World") //returns "Hello World"
 $text:=$f.call(Null;"Welcome to";String(Year of(Current date))) //returns "Welcome to 2026" (for example)

Parameters to a single method

For more convenience, when the formula is made of a single project method, parameters can be omitted in the formula object initialization. They can just be passed when the formula is called. For example:

 var $f : 4D.Formula

 $f:=Formula(myMethod)
  //Writing Formula(myMethod($1;$2)) is not necessary
 $text:=$f.call(Null;"Hello";"World") //returns "Hello World"
 $text:=$f.call() //returns "How are you?"

  //myMethod
 #DECLARE ($param1 : Text; $param2 : Text)->$return : Text
 If(Count parameters=2)
    $return:=$param1+" "+$param2
 Else
    $return:="How are you?"
 End if

Parameters are received within the method, in the order they are specified in the call.

Formula object

.apply() : any .apply( thisObj : Object { ; params : Collection } ) : any executes the function object to which it is applied, passing parameters as a collection, and returns the resulting value
.call() : any .call( thisObj : Object { ; ...params : any } ) : any executes the function object to which it is applied, with one or more parameter(s) passed directly, and returns the resulting value
.source : Text contains the source code of the function as text

.apply()

History

Release	Changes
21 R3	Support of 4D.Methods objects
17 R3	Added

.apply() : any
.apply( thisObj : Object { ; params : Collection } ) : any

Parameter	Type		Description
thisObj	Object	->	Object to be returned by the This command in the function
params	Collection	->	Collection of values to be passed as parameters to the function
Result	any	<-	Value from function execution

Description

The .apply() function executes the function object to which it is applied, passing parameters as a collection, and returns the resulting value.

In the thisObj parameter, you can pass a reference to the object to be used as This within the function. Pass Null if you do not want to use This but you want to send parameters.

You can pass a collection to be used as parameters in the function using the optional params parameter:

• in 4D.Formula objects, parameters are passed in $1...$n in the formula.
• in other 4D.Function objects such as 4D.Method objects, parameters are passed in declared method parameters.

Note that .apply() is similar to .call() except that parameters are passed as a collection. This can be useful for passing calculated results.

Example 1

 var $f : 4D.Formula
 $f:=Formula($1+$2+$3)

 $c:=New collection(10;20;30)
 $result:=$f.apply(Null;$c) // returns 60

Example 2

 var $calc : 4D.Formula
 var $feta; $robot : Object
 $robot:=New object("name";"Robot";"price";543;"quantity";2)
 $feta:=New object("name";"Feta";"price";12.5;"quantity";5)

 $calc:=Formula(This.total:=This.price*This.quantity)

 $calc.apply($feta) // $feta={name:Feta,price:12.5,quantity:5,total:62.5}
 $calc.apply($robot) // $robot={name:Robot,price:543,quantity:2,total:1086}

.call()

History

Release	Changes
21 R3	Support of 4D.Methods objects
17 R3	Added

.call() : any
.call( thisObj : Object { ; ...params : any } ) : any

Parameter	Type		Description
thisObj	Object	->	Object to be returned by the This command in the function
params	any	->	Values to be passed as parameters to the function
Result	any	<-	Value from function execution

Description

The .call() function executes the function object to which it is applied, with one or more parameter(s) passed directly, and returns the resulting value.

In the thisObj parameter, you can pass a reference to the object to be used as This within the function.

You can pass values to be used as parameters in the function using the optional params parameter:

• in 4D.Formula objects, parameters are passed in $1...$n in the formula.
• in 4D.Method objects, parameters are passed in declared method parameters.

Note that .call() is similar to .apply() except that parameters are passed directly.

Example 1

 var $f : 4D.Formula
 $f:=Formula(Uppercase($1))
 $result:=$f.call(Null;"hello") // returns "HELLO"

Example 2

 $o:=New object("value";50)
 $f:=Formula(This.value*2)
 $result:=$f.call($o) // returns 100

.source

History

Release	Changes
21 R3	Support of 4D.Methods objects
18 R2	Added

.source : Text

Description

The .source property contains the source code of the function as text.

The returned value is the original text used to create the 4D.Formula or 4D.Method object but reformatted.

This property is read-only.

Example

 var $of : 4D.Formula
 var $tf : Text
 $of:=Formula(String(Current time;HH MM AM PM))
 $tf:=$of.source //"String(Current time;HH MM AM PM)"