# OPC UA Call Function

**URL:** <https://forum.inductiveautomation.com/t/opc-ua-call-function/25643>\
**Category:** Ignition\
**Created:** [June 7, 2019, 3:52pm UTC](https://forum.inductiveautomation.com/t/opc-ua-call-function/25643 "2019-06-07T15:52:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![roland.scheuer](https://avatars.discourse-cdn.com/v4/letter/r/c57346/32.png) [@roland.scheuer](https://forum.inductiveautomation.com/u/roland.scheuer)\
**Post date:** [June 7, 2019, 3:52pm UTC](https://forum.inductiveautomation.com/t/opc-ua-call-function/25643/1 "2019-06-07T15:52:19Z")

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Hello,  
Im new to ignition and i want to ask if it is possible to call OPC UA function on click or Variable change? I cant find the possibility.

Mann thanks in advance.  
Br  
Roland

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [June 7, 2019, 3:54pm UTC](https://forum.inductiveautomation.com/t/opc-ua-call-function/25643/2 "2019-06-07T15:54:20Z")

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Ignition 8 has [system.opcua.callMethod](https://docs.inductiveautomation.com/display/DOC80/system.opcua.callMethod), which you could call from a script on a button or tag change script.

It’s a little difficult to use because you have to know everything about the method you want to call ahead of time. There’s no way to discover methods or their arguments in the OPC browser or anywhere else in the UI.

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<div class="post-metadata">

**Author:** ![roland.scheuer](https://avatars.discourse-cdn.com/v4/letter/r/c57346/32.png) [@roland.scheuer](https://forum.inductiveautomation.com/u/roland.scheuer)\
**Post date:** [June 7, 2019, 3:58pm UTC](https://forum.inductiveautomation.com/t/opc-ua-call-function/25643/3 "2019-06-07T15:58:37Z")

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Hey thanks for this Ultrafast answer 🙂 i will try it as soon as possible, but it looks like thats exactly what i was searching for.

Thanks!

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<div class="post-metadata">

**Author:** ![roland.scheuer](https://avatars.discourse-cdn.com/v4/letter/r/c57346/32.png) [@roland.scheuer](https://forum.inductiveautomation.com/u/roland.scheuer)\
**Post date:** [June 7, 2019, 7:14pm UTC](https://forum.inductiveautomation.com/t/opc-ua-call-function/25643/4 "2019-06-07T19:14:06Z")

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Hi Kevin,

i seems the namespace system.opcua is not availible on button click. do i miss something?

br,  
Roland

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<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [June 7, 2019, 7:33pm UTC](https://forum.inductiveautomation.com/t/opc-ua-call-function/25643/5 "2019-06-07T19:33:08Z")

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Ah, right… it’s only available in the gateway scope. It will work from a tag change script. If you need to use a button then you’ll have to define a gateway handler and use system.util.sendMessage to send a message to the handler.