# SFC Transition Expression Reference

**URL:** <https://forum.inductiveautomation.com/t/sfc-transition-expression-reference/65756>\
**Category:** Ignition\
**Tags:** ignition81\
**Created:** [October 27, 2022, 1:34pm UTC](https://forum.inductiveautomation.com/t/sfc-transition-expression-reference/65756 "2022-10-27T13:34:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![mlwalter](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@mlwalter](https://forum.inductiveautomation.com/u/mlwalter)\
**Post date:** [October 27, 2022, 1:34pm UTC](https://forum.inductiveautomation.com/t/sfc-transition-expression-reference/65756/1 "2022-10-27T13:34:39Z")

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I've created a python class that I I've called criteria. It has two properties, HighLimit and LowLimit. I was able to create a chart scoped parameter with this class, but I'm not able to reference the underlying properties. The transition that I tried was {runningTime} \> {criteria.HighLimit}. Am I missing something syntax-wise or is it not possible to do this?

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/9/193745bda21789607f9111a28151084eaf3ec8e6.png)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/7/d/7d0c2a3dc7f7438ec0c9c16b364bd3246ff88d20.png)

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**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [October 27, 2022, 3:25pm UTC](https://forum.inductiveautomation.com/t/sfc-transition-expression-reference/65756/2 "2022-10-27T15:25:42Z")

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> [@mlwalter](#):
>
> {runningTime} \> {criteria.HighLimit}

As in, you just wrote that into a transition block? I don't think that will work. I think you'll have to use scripting (directly or indirectly) to use your custom class. You might be able to use `runScript` and pass in `criteria` as a parameter, though?

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<div class="post-metadata">

**Author:** ![mlwalter](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@mlwalter](https://forum.inductiveautomation.com/u/mlwalter)\
**Post date:** [October 27, 2022, 3:53pm UTC](https://forum.inductiveautomation.com/t/sfc-transition-expression-reference/65756/3 "2022-10-27T15:53:09Z")

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Yes, I put that directly into the transition expression. My other thought was to use the function I've created in the class (evaluatePassFail) which returns a boolean in the step S1 to set a chart scoped variable and base the transition on that variable (since it seems to handle non-Object items perfectly fine).