# System tag write blocking

**URL:** <https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240>\
**Category:** Ignition\
**Tags:** perspective\
**Created:** [February 10, 2021, 3:16pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240 "2021-02-10T15:16:36Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![michael.black](https://avatars.discourse-cdn.com/v4/letter/m/ee7513/32.png) [@michael.black](https://forum.inductiveautomation.com/u/michael.black)\
**Post date:** [February 10, 2021, 3:16pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/1 "2021-02-10T15:16:36Z")

</div>

I have a container with 4 objects in it and I want to control visibility on the container based on if the mouse is over the container or not. I created a custom property called HighlightVis for the coordinate container.  
I created two event scripts, one based on onMouseOver and the other based on onMouseOut. I then assigned a script for each one with MouseOver writing a true value to HighlightVis and MouseOut writing a false value to HighlightVis. It does not seem to be working.

Here is what I have for the onMouseOut script:  
system.tag.writeBlocking(self.custom.HighlightVis, “false”)  
Here is the onMouseOver script:  
system.tag.writeBlocking(self.custom.HighlightVis, “true”)

What am I missing?

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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:** [February 10, 2021, 3:18pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/2 "2021-02-10T15:18:52Z")

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Couple things.

1. `writeBlocking` expects array/list arguments
2. you should not use blocking calls like this from a UI thread because it will freeze the UI while it executes.

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<div class="post-metadata">

**Author:** ![michael.black](https://avatars.discourse-cdn.com/v4/letter/m/ee7513/32.png) [@michael.black](https://forum.inductiveautomation.com/u/michael.black)\
**Post date:** [February 10, 2021, 3:22pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/3 "2021-02-10T15:22:46Z")

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Thanks. So how would I go about getting this done?

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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:** [February 10, 2021, 3:26pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/4 "2021-02-10T15:26:12Z")

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Ah, is this Perspective or Vision?

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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:** [February 10, 2021, 3:27pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/5 "2021-02-10T15:27:23Z")

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`writeBlocking` is for writing to tags… the first argument would be a list of tag paths.

It seems like you just need to do this in your scripts:

```auto
self.custom.HighlightVis = 0

```

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<div class="post-metadata">

**Author:** ![michael.black](https://avatars.discourse-cdn.com/v4/letter/m/ee7513/32.png) [@michael.black](https://forum.inductiveautomation.com/u/michael.black)\
**Post date:** [February 10, 2021, 3:28pm UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/6 "2021-02-10T15:28:06Z")

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perspective. will try that simple line as see if it works.

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<div class="post-metadata">

**Author:** ![Yfactor](https://avatars.discourse-cdn.com/v4/letter/y/e79b87/32.png) [@Yfactor](https://forum.inductiveautomation.com/u/Yfactor)\
**Post date:** [February 21, 2021, 12:58am UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/7 "2021-02-21T00:58:22Z")

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Hi, @Kevin.Herron,  
how do we block write with custom property values like how we do it on tags?

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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:** [February 21, 2021, 1:00am UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/8 "2021-02-21T01:00:46Z")

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There’s no need, the assignment is blocking and should should take effect immediately.

Is there something you are seeing that makes you think otherwise?

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<div class="post-metadata">

**Author:** ![Yfactor](https://avatars.discourse-cdn.com/v4/letter/y/e79b87/32.png) [@Yfactor](https://forum.inductiveautomation.com/u/Yfactor)\
**Post date:** [February 21, 2021, 1:17am UTC](https://forum.inductiveautomation.com/t/system-tag-write-blocking/43240/9 "2021-02-21T01:17:45Z")

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Ok,  
oh I was thinking like let say I have (bool)  
value1, value2, value3, value4 in my custom properties  
and when I press a button,  
I want to write true to value1, value2, value3, value4  
but if something happens let say error when writing on value2 than don’t write to all of them…?