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 stringwill 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:
