Expression Style
Overview
In general, PhixFlow ignores all spacing around the functional elements. However spacing and layout makes the meaning much clearer for you to read. Adopting a common, shared, standard style for all expressions, scripts and macros makes it easier to read them and quickly understand what they are doing.
This page provides recommended styles for writing expressions.
General
Item properties
All items in PhixFlow have a description property. We recommend you add a description to any item you create.
Anybody looking at a model or application will first look at the descriptions of the items within it. For example, in an analysis model, they should be able to discern the flow and the high-level logic of the model just from the descriptions.In analysis models, the table description should explain the use of input or output multipliers. This it typically a significant part of any model.
Ensure that attributes that represent the same thing in different tables have the same name. PhixFlow needs this when processing merges and for a union in a calculate table.
Formatting expressions
Add comments to document your expression using:
// for a single line comment
/* ... */ to enclose multiline comments
Include blank lines between statements
Use spaces within expressions
Indent sub-clauses by 4 spaces
Naming Conventions
Multi-word attribute and pipe names should be in camel case.
All user-defined variables must start with the $ character.
For multi-word variable names, use no spaces and camel case.
It can be useful to know whether a variable is used in other expressions. As there is no way to check this, we recommend using the following naming convention:
To distinguish between $-variables that are:
only used in the current expression or attribute, use a lowercase first letter, for example
$percent.
These are sometimes called local.used in other expressions or attributes, use an uppercase first letter, for example
$Percent.
These are sometimes called global.
Examples | |
|---|---|
attribute |
|
pipe |
|
global $-variable |
|
local $-variable |
|
Camel case uses an uppercase letter for the start of each sub-word, for example $ThisIsCamelCase. As we recommend having no spaces, this makes the name readable.
Adding Comments
It is always a good idea to add comments to your scripts to explain its steps. Comments help anyone who needs to modify the script in future.
There are two ways to tell PhixFlow that a line is a comment, and can be ignored.
Notation | Use for |
|---|---|
| short comments up to 1 line |
| multi-line comments |
Comments are not evaluated when the code is run.
Example 1
/* Get the discount rate that should apply to
the calls that match the filter conditions */
$discountRate = discount.rate,
// Now apply the discount
$value = $value * ( 1 - $discountRate)
...Example 2
/* Evaluates to 1 if AppleHarvest Date is Before 1st January 2021*/
if( _out.AppleHarvestDate < _toDate('20210101'), 1,
// else, 0 if it is not
0
)Layout for if()
Simple
For simple if() statements we recommend the following style of layout:
When a statement in an if() clause is more than 1 line, wrap them in a do(), for example:
// Example code layout
if( condition expression,
do(
Statement 1,
Statement 2,
... Statement n
),
// else
Statement A
)Note that:
the condition is on the same line as if(
the closing brackets are always lined up with the start of the statement (see the do() and if() statements above)
Complex
For more complex if() statements we recommend the following style and that comments are added:
// Short description on what is being achieved when the if statement is true
if ( $foo > 10 &&
$bar == "X" &&
( $baz == "Y" ||
$qux == "Z" ),
// description of what the statement is doing
do (
Statement 1
),
// else, description of what the statement is doing
Statement 2
)Note that:
multiple conditions are on separate lines
indents are used to show conditions grouped by brackets - this makes it easy to see what the conditions are and helps avoid brackets being placed in the wrong place
Layout for switch()
Simple
For simple switch statements we recommend the following layout:
switch(
[ condition expression 1, Statement 1 ],
[ condition expression 2, Statement 2 ],
// default
_NULL
)
// example
switch(
[ $foo > 100, $x = "HIGH" ],
[ $bar > 50, $x = "MEDIUM" ],
// default
$x = "LOW",
)Complex
For switch statements that perform more advanced activities we recommend the following layout:
switch (
// description of what the statement is doing
[ $foo == 100,
$x = "HIGH"
],
// description of what the statement is doing
[ $bar == 50,
do (
$x = "Medium",
$x = toUpper($x)
)
]
// default
do (
$x = "LOW"
)
)