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Actions have a dynamic field where you can write an expression to check that the action has run correctly.
Streams have several dynamic fields where you affect the data records in the stream
Expression Editor
Usually a dynamic field is expecting an expression. In some cases, a dynamic field expects different code, such as an SQL statement. If you want to use an expression in this type of field, enclose it in curly brackets.
Expressions can also include variables. Some internal variables are defined in PhixFlow. The internal variables that you can use depends on the context. You can also create your own variables. As these are prefixed with the $-symbol they are called $-variables.
To find out what code a dynamic field expects, or which internal variables are available, check the help for the properties tab in which you are working. At the top of the properties tab, click
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Large Editor
When working on large expressions or scripts it can be useful to use the option,
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As well as internal variables, PhixFlow has lots of functions that you can use in expressions.
Functions
The pages in this topic provide information on writing your own expressions, from simple assignments to complex looping operations.
| Expression Basics | Basic operations (+, -, *, /), $-variables, variable types, assignment statements, object types and commenting scripts. |
| Expression Style | A summary of the recommend scripting styles e.g. how to lay out an if clause and how best to name variables |
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 */
)
The pages in this topic are: