This page is for data modellers and application designers who need to reuse segments of scripts or expressions in multiple places.

Overview

Sometimes we might want to write our own expressions that can be used time and again. To do this:

1. In the PhixFlow repository, add a new Macro item and name it.
2. Add minimum and maximum parameters.
3. Copy in the expression you want to reuse.
4. To make an expression reusable in different contexts, change all references to named items to arguments, such as , $args[1]
5. To use the macro in an expression, specify: macro_name(argument_name).

For example, we want to reuse an expression:

if( out.AppleHarvestDate < 1, 1, 0)

Create a macro called isGreaterThanOne that contains the expression:

if($args[1] > 1, 1, 0)

To use the macro, replacing $arg[1] with the pipe and attribute name _out.AppleHarvestDate:

isGreaterThanOne(_out.AppleHarvestDate)

For information about writing expressions and PhixScripts, see the Expressions and PhixScripts topic.

Macro Properties

Basic Settings

Expression

Example

Thie following macro is called padCost. It takes 1 parameter - a numeric value. It checks to see if the numeric value is missing a 0 before a decimal point. If so, it adds the 0 and returns the string. It can be called anywhere in PhixFlow that an expression can be entered. For example, by entering padCost(".977")

do(
  $val = $args[1],
  if( startsWith($val, "."),
    // if the cost is positive, add a zero onto the beginning
    "0" + $val,
    // ELSE
    if( startsWith($val, "-."),
      //if the cost is negative, replace the -. with a -0.
      "-0." + substring($val,3),
      //ELSE
      $val
    )
  )
)

See also: