Typecasting / coercion?

Ignition
1

I’m trying to do the following in a project script:

def debugTest(): tester = system.tag.read("[Client]prevSt") tester=tester + 1 system.tag.write("[Client]prevSt",tester)

but I get:

[code]Traceback (most recent call last):
File “”, line 1, in
File “module:project.stateMachine”, line 17, in debugTest
TypeError: unsupported operand type(s) for +: ‘com.inductiveautomation.ignition.common.sqltags.BasicTagValue’ and ‘int’

[/code]

The help file speaks of the toInt command when looking to do typecasting. A bit of rearranging gives me:

def debugTest(): tester = system.tag.read("[Client]prevSt") intTester=toInt(tester) + 1 system.tag.write("[Client]prevSt",intTester)

Brilliant, yes?

No:

[code]Traceback (most recent call last):
File “”, line 1, in
File “module:project.stateMachine”, line 17, in debugTest
NameError: global name ‘toInt’ is not defined

[/code]

So how do I read a tag of type int, add one to it, and write it back from within a project script? This should be scripting 101, but I am at a loss.

Thanks!

Joe

2

The value you get back from system.tag.read is a “qualified value”, a structure that contains the value, quality, and timestamp. You need to access the value attribute before attempting to use it the way you are.

3

Hi,
Kevin is right. It should be like this.

def debugTest():
   tester = system.tag.read("[Client]prevSt").value
   tester=tester + 1
   system.tag.write("[Client]prevSt",tester)

Notice that the “value” property was used.