Method

A 4D.Method object contains a piece of code that is created from text source and can be executed. 4D.Method methods always execute in interpreted mode, regardless of the project running mode (interpreted/compiled). This feature is especially designed to support dynamic, on-the-fly execution of code snippets.

A 4D.Method object is created with the 4D.Method.new() function.

4D.Method objects inherit from the 4D.Function class. Thus, to execute the method object, you can:

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

See examples in the Executing code in Function objects paragraph.

Related blog post

Execute Code from Text with 4D.Method

Examples

Basic dynamic method creation

var $myCode : Text
$myCode:="#DECLARE ($number1:Integer;$number2:Integer):Integer"+Char(13)+"return $number1*$number2"

var $o:={}
$o.multiplication:=4D.Method.new($myCode) //put object in a property
var $result2:=$o.multiplication(2;3) // 6

var $result3:=4D.Method.new($myCode).call(Null; 10; 5) // 50

Using This inside method code

var $myCode:="#DECLARE ($str1:text):text"+Char(13)+"return $str1+This.name"

var $o:={name: "John"}
$o.concat:=4D.Method.new($myCode)

var $result : Text
$result:=$o.concat("Hello ") // $result is "Hello John"

Using a text file with syntax checking

//4d method stored in a text file
var $newBusinessRules:=New shared object
Use ($newBusinessRules)
	$newBusinessRules.taxRate:=0.2
	$newBusinessRules.discountFormula:="price * quantity * discountRate"
	$newBusinessRules.approvalThreshold:=10000
	$newBusinessRules.freeShippingThreshold:=150
	$newBusinessRules.defaultCurrency:="EUR"
End use 

Use (Storage)
	Storage.businessRules:=$newBusinessRules
End use  

This method is called in the code:

var $myFile:=File("/DATA/BusinessRules.4dm")

var $myMethod:=4D.Method.new($myFile.getText())
// Syntax errors verification
If ($myMethod.checkSyntax().success)
   $myMethod.call()
End if 

Method Object

4D.Method objects provide the following properties and functions:

.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
.checkSyntax() : Object checks the syntax of the source code of the 4D.Method object and returns a result object
.name : Text contains the name of the 4D.Method object, if it was declared in the name parameter of the new() constructor
.source : Text contains the source code of the function as text

4D.Method.new()

History

Release	Changes
21 R3	Added

4D.Method.new( source : Text {; name : Text } ) : 4D.Method

Parameter	Type		Description
source	Text	->	Textual representation of a 4D method to be encapsuled as an object
name	Text	->	Name of the method to display in the debugger. If omitted, the method name will be displayed as "anonymous"
Result	4D.Method	<-	New Method shared object

Description

The 4D.Method.new() function creates and returns a new 4D.Method object built from the source code.

In the source parameter, pass the 4D source code of the method as text. All end-of-line characters are supported (LF, CR, CRLF) using the Char command or an escape sequence.

In the optional name parameter, pass the name of the method to be displayed in the 4D debugger or Runtime explorer. If you omit this parameter, the method name will appear as "anonymous".

tip

Giving a name to your method is recommended if you want to:

• use persistent method name in the Custom watch pane of the Debugger (anonymous methods are not persistent in the debugger).
• handle the volatile method using commands such as Method get path and Method resolve path (anonymous methods don't have paths).

The resulting 4D.Method object can be checked using checkSyntax() and executed using (), .apply() or .call().

note

Named volatile method objects are not project methods, they cannot be called by commands such as EXECUTE METHOD. On the other hand, since they inherit from the 4D.Function class, they can be used anywhere a 4D.Funciton object is expected.

Example

var $m:=4D.Method.new("#DECLARE ($t : Text) : Text \nreturn Uppercase($t)")

var $res:=$m.call(Null; "hello world")  //HELLO WORLD

.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

var $coll:=[10; 2]
var $myCode:="#DECLARE ($number1:Integer;$number2:Integer):Integer\n"+\
"return $number1*$number2"

$m:=4D.Method.new($myCode; "m_multiple")
var $result:=$m.apply(Null; $coll) //20

.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

 var $m : 4D.Method
 var $myCode:="#DECLARE ($number1:Integer;$number2:Integer):Integer\n"+\
"return $number1*$number2"

$m:=4D.Method.new($myCode; "m_multiple")
var $result:=$m.call(Null; 10; 5) //50

.checkSyntax()

History

Release	Changes
21 R3	Added

.checkSyntax() : Object

Parameter	Type		Description
Result	Object	<-	Syntax check result object

Description

The .checkSyntax() function checks the syntax of the source code of the 4D.Method object and returns a result object.

The Result object contains the following properties:

Property		Type	Description
success		Boolean	True if no syntax error was detected, false otherwise
errors		Collection of objects	Available only in case of error or warning. Collection of objects describing errors or warnings
	[].isError	Boolean	Error if True, warning otherwise
	[].message	Text	Error or warning message
	[].lineNumber	Integer	Line number of error in the code

Example

var $m : 4D.Method
var $check : Object
$m:=4D.Method.new("var $a:=2026\r$a:=current date")
$check:=$m.checkSyntax()
If ($check.success=False)
	ALERT("Syntax error: "+$check.errors[0].message)
End if 

.name

History

Release	Changes
21 R3	Added

.name : Text

Description

The .name property contains the name of the 4D.Method object, if it was declared in the name parameter of the new() constructor. Otherwise, the property is not returned.

This property is read-only.

.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 $myCode:="#DECLARE ():Real\n"+\
"return random*current time"
$m:=4D.Method.new($myCode)
$src:=$m.source //"#DECLARE() : Real\rreturn Random*Current time"