App development on the Prime

[CheshireChris]

Another problem I faced was how to read the value of an app variable if it existed, and create it if it didn’t exist, so I could do one-time initialisation of my data, but not overwrite the value the user had entered on subsequent runs. The solution I came up with, to do this for a variable called “Lat” (the user’s geographical latitude) was this:

Code:


// If variable “Lat” doesn’t exist, create it with a default value
IF POS(AVars,“Lat”)==0 THEN
  AVars(“Lat”):=53;
END;

This uses the fact that AVars used with no parameters returns a list of currently existing app variables.