PhixFlow is a low-code, application-development platform. Using PhixFlow, you can create applications starting with the user interface, rather than requiring software developers to code all the functionality. However, PhixFlow sometimes needs code-like instruction to achieve the functionality you need. This is done with short expressions or longer scripts.
Expressions are short pieces of code that perform a function within a PhixFlow model, application or taskplan. Good starting pages for learning how to write expressions are:
Arguments
Arguments can contain several types of functions. (To find the correct syntax for an expression - find it in the list below or search in confluence)
- Another jep expression eg. if( _out.AppleHarvestDate < toDate('20210101'), 1, 0). Here we see an expression within an expression. toDate(converts the string 20210101 into a date 01-01-2021)
- Internal Variables (eg _out.) _out. signals that AppleHarvestDate is being sourced from the same stream as the attribute on which you are writing an expression for and that it has therefore already been calculated. Also frequently used is the name of a pipe that goes into a stream followed by a . eg in.AppleHarvestDate which signals that AppleHarvestDate is being sourced down a pipe going into the stream called 'in'. The internal variable preceding an attribute name should reflect where the attribute is being source from. There are many other internal variables, see Internal Variables.
- Regular Expressions - Regular expressions can be used to match patterns within strings or arrays as arguments within jep expressions, for example replaceAll, replaceFirst and matches. See Regexp ToDelete.
- Simple integers or strings. In the above case 1 and 0 are simple integers. They tell PhixFlow to return the number 1 if NumberOfApples > 1 and 0 if it is not. A string could be returned instead eg. if(_out.NumberOfApples > 1, 'True', 'False') would return the string True if NumberOfApples >1 and False if it is not. Note strings need to be wrapped in ' marks.
Additionally it is good practise to add comments to code to allow other people to understand the code you have written. Comments are not evaluated when the code is run. To add a comment start a new line and begin it with */ and end it with */.
eg. if(_out.AppleHarvestDate < toDate('20210101'), 1,
/* Evaluates to 1 if AppleHarvest Date is Before 1st January 2021*/
0
/* and to 0 if it is not */
)
Macros
See Macro
Sometimes we might want to write our own expressions that can be used time and again. To do this we can write a Macro. Instead of a writing the name of each attribute in the expression, instead make it generic by writing $args[1], $args[2] etc.
For example we could write a Macro called isGreaterThanOne with the expression if($args[1] > 1, 1, 0). Then instead of writing if( out.AppleHarvestDate < 1, 1, 0) we could write isGreaterThanOne(_out.AppleHarvestDate). Where _out.AppleHarvestDate is set to be $args[1] in this case. If what ever $args[1] is set to be is > 1 it will return 1 else it will return 0.
The pages in this topic are: