# Perspective Components' Value Binding **URL:** \ **Category:** Ignition\ **Tags:** perspective\ **Created:** [December 28, 2023, 1:37am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563 "2023-12-28T01:37:48Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Roman\_Rozenshteyn](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@Roman\_Rozenshteyn](https://forum.inductiveautomation.com/u/Roman_Rozenshteyn)\ **Post date:** [December 28, 2023, 1:37am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/1 "2023-12-28T01:37:48Z")
Hi all, I'm using one of the standard Perspective components for my motor faceplate and would like to bind a tag to show as the text of the value property, which works as expected. Now I would like to add a unit to said text - something like: 10 m/s, where the 10 is my tag value. I tried the following in a script transform: def transform(self, value, quality, timestamp): value = toString(value) + 'ft/s' return value I tried with and without the toString function and also different variations of it. Nothing worked. Why doesn't this work and what can I do about it? Thanks in advance. ---
**Author:** ![Ryan\_Allen](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan_allen/32/47013_2.png) [@Ryan\_Allen](https://forum.inductiveautomation.com/u/Ryan_Allen)\ **Post date:** [December 28, 2023, 1:53am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/2 "2023-12-28T01:53:27Z")
Try just str() instead of tostring() ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 28, 2023, 2:02am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/3 "2023-12-28T02:02:34Z")
Not sure why you would use a script transform for this, from memory they are slower to run, so they will hog more resources in bulk. I would just do it with an expression: `{value} + ' m/s'` Supposed to run faster, and it's simpler to read. ---
**Author:** ![Transistor](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/transistor/32/3380_2.png) [@Transistor](https://forum.inductiveautomation.com/u/Transistor)\ **Post date:** [December 28, 2023, 2:11am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/4 "2023-12-28T02:11:20Z")
An expression binding would be as simple as, `{[default]MyTag} + " m/s"` And if you've specified the EngUnit when creating the tags (which I'm sure you have) then you can use, `{[default]MyTag} + " " + {[default]MyTag.EngUnit}` Note that @David_Stone and I are inserting a space between the numerical value and the units as they're separate "words" and it improves readability. It's a recommendation on the SI standard but I don't know if there's an equivalent for the system still used in some of the colonies. General comment: I would always try and use a separate label for the units for a few reasons: - It allows the numbers to be right-aligned and the units left-aligned so that columns of values containing different units remain tabular even if the lengths of the units varies. - You can use a different font weight / size / shade for the units to tone them down and reduce visual clutter. The operator will get to know the units but the numerical value is what's important to them. - Keeping them separate means the value can be referenced by another component or expression without another call to the tag. When you mix in a string this gets messy. ---
**Author:** ![Transistor](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/transistor/32/3380_2.png) [@Transistor](https://forum.inductiveautomation.com/u/Transistor)\ **Post date:** [December 28, 2023, 2:20am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/5 "2023-12-28T02:20:30Z")
@Roman - see [How to post code on this forum](https://forum.inductiveautomation.com/t/wiki-how-to-post-code-on-this-forum/77831). ---
**Author:** ![Roman\_Rozenshteyn](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@Roman\_Rozenshteyn](https://forum.inductiveautomation.com/u/Roman_Rozenshteyn)\ **Post date:** [December 28, 2023, 11:25pm UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/7 "2023-12-28T23:25:33Z")
Great advice but, I'm not sure how this would be implemented with parameter passing. I tried the most intuitive way, by go through an expression transform, which obviously didn't work out for me: `{value} + {value.EngUnit}` Is there a solution to this issue? ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 28, 2023, 11:27pm UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/8 "2023-12-28T23:27:27Z")
When passing a tag value, pass the tag path instead, and reference everything with that instead of a passed value. ---
**Author:** ![Roman\_Rozenshteyn](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@Roman\_Rozenshteyn](https://forum.inductiveautomation.com/u/Roman_Rozenshteyn)\ **Post date:** [December 28, 2023, 11:41pm UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/9 "2023-12-28T23:41:11Z")
I think we're on the same page but maybe I'm not explaining myself well. Let me try this again. How do I replace the literal in the expression field with a pointer to the EngUnit: ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/d/4/d4f59a14f1b661feece4da3f5f272d182a7e98a7.png) ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 28, 2023, 11:50pm UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/10 "2023-12-28T23:50:54Z")
Because you aren't passing the actual path to the tag as the parameter, use a property binding to `view.params.tagPath`, then do an expression transform: `{value} + '/FeedbackStates/stsVelocityFb'` Under that, do another expression transform: `tag({value}) + ' ' + tag({value} + '.EngUnit') ` Basically you form the path to the tag, then you reference it, and the EngUnit as well. If you were just passing a complete tag path, you would just need the second transform. ---
**Author:** ![Transistor](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/transistor/32/3380_2.png) [@Transistor](https://forum.inductiveautomation.com/u/Transistor)\ **Post date:** [December 29, 2023, 12:03am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/11 "2023-12-29T00:03:59Z")
Create a `tagPath` parameter on the view. Create a **property binding** on the label like this: ![Tag value and units](https://us1.discourse-cdn.com/inductiveautomation/original/3X/8/f/8f7dac71b3b44679df9b63306987f88f2756e5cc.png) You can get fancier and use the tag's FormatString too: ```auto numberFormat( tag({value}), tag({value} + ".FormatString") ) + " " + tag({value} + ".EngUnit") ``` In my example this would result in `14.42 m/s/s`. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [December 29, 2023, 1:42am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/12 "2023-12-29T01:42:29Z")
Oy! Really @Transistor, @David_Stone ? The engineering unit retrieval belongs in a separate custom property, which then can be referenced in the original indirect tag binding's transform. (And format string, too, if wanted.) If you find yourself using the `tag()` expression function outside an actual expression tag, you are screwing up. ---
**Author:** ![Transistor](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/transistor/32/3380_2.png) [@Transistor](https://forum.inductiveautomation.com/u/Transistor)\ **Post date:** [December 29, 2023, 3:04am UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/13 "2023-12-29T03:04:16Z")
Thanks, Phil. How would that work? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [December 29, 2023, 1:38pm UTC](https://forum.inductiveautomation.com/t/perspective-components-value-binding/83563/14 "2023-12-29T13:38:20Z")
The Engineering Unit binding, on a component custom property, looks like this: ![20231229_0835](https://us1.discourse-cdn.com/inductiveautomation/original/3X/a/a/aac5ff1c34b6fc81f80388ba0622c92400a04a17.png) The Format String binding is similar, also on a component custom property. Then the text property binding (I used a label component) would look like this: ![20231229_0834](https://us1.discourse-cdn.com/inductiveautomation/original/3X/8/d/8dbd7a698c19cbe069c7571354b04c30c0c6442b.png) No `tag()` function! Everywhere in a UI you **think** you need a `tag()` function, train yourself to split off a custom property with an indirect binding.