Formula from string

History

Release	Changes
20 R3	Support of context parameter
17 R6	Renamed New formula from string -> Formula from string
17 R3	Added

Formula from string( formulaString : Text ) : 4D.Function
Formula from string( formulaString : Text ; context : Longint ) : 4D.Function

Parameter	Type		Description
formulaString	Text	→	Text formula to be returned as object
context	Number	→	sk execute in current database (default) or sk execute in host database
Result	4D.Function	←	Native object encapsulating the formula

Description

The Formula from string command creates a 4D.Function object based upon the formulaString and, optionnally, a context. formulaString can be as simple as a single value or complex, such as a project method with parameters.

This command is similar to Formula, except that it handles a text-based formula and allows to define an execution context. It is usually recommended to use the Formula command, except if the original formula was expressed as text (e.g., stored externally in a JSON file), or if you want to create a formula in a host database while calling Formula from string from a component. Using syntax with tokens is highly advised with this command.

Because local variable contents can not be accessed by name in compiled mode, they can not be used in formulaString. An attempt to access a local variable with Formula from string will result in an error (-10737).

If the formula is created in a component, you might consider using the context parameter. By default, since formulas are executed in the context in which they were created, it will not be able to call a variable, function, or a non-shared method of the host database. In this case, you can pass the sk execute in host database constant in the context parameter to execute the 4D.Function object in the context of the host database. The following constants are available:

Constant	Type	Description
sk execute in current database	Integer	(default) The formula will be executed in the context it was created
sk execute in host database	Integer	The formula will be executed in the host database context

Example

The following code will create a dialog accepting a formula in text format:

 var $textFormula : Text
 var $f : 4D.Function
 $textFormula:=Request("Please type a formula")
 If(ok=1)
    $f:=Formula from string($textFormula)
    ALERT("Result = "+String($f.call()))
 End if

...and execute the formula:

See also

Formula
Parse formula

Properties

Command number	1601
Thread safe	✓