[QGIS-Developer] Variable syntax: $ vs @
sfkeller at gmail.com
Fri Jun 30 03:21:08 PDT 2017
Only partially related to this thread as a shy reminder:
My intern Simran recently has made a pull request [*] for your nice
Expressions Plus Plugin QGIS plugin.
These are the proposed additional functions:
* max_incremented() - an "autoincrement" id function
* hstore - support of a key-value pair set/string
* nullif() - returns None if arg_1 equals to arg_2 otherwise arg_1
* get_env_variable() and set_env_variable()
These expression functions could be of interest for workshops like the
2017-06-19 14:36 GMT+02:00 Neumann, Andreas <a.neumann at carto.net>:
> Hi Nathan,
> Thank you for the explanation. Makes sense. I will pass this on in the
> On 2017-06-19 14:12, Nathan Woodrow wrote:
> Hey Andreas,
> They are really two different things. $geometry is really a function that
> takes no arguments. This has been deprecated in favour calling with () e.g
> geometry(). @ is only for variables.
> So you can explain it that $ used to be a shorthand way of calling a
> function that took no arguments which has now been replaced with () at the
> end to call it. $area = area(). This becomes important because now we
> support optional arguments meaning you can take 0 to N arguments.
> - Nathan
> On Mon, Jun 19, 2017 at 9:53 PM, Neumann, Andreas <a.neumann at carto.net>
>> While preparing for a workshop on expressions I wonder how to explain why
>> some variables are referenced with the $ sign (like $geometry) while other
>> variables start with the @ sign, like @row_number, @layer_name.
>> I know that it has historical reasons and that variables with the @ sign
>> are newer and are implemented using a different technology.
>> But are there plans to get rid of the old $ sign notation and move
>> everything to the @ sign notation?
>> Just wonder how I best explain this to the participants of the workshop.
>> Thanks for your reply,
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