# Help Needed Populating Dropdown with String Array

**URL:** <https://forum.inductiveautomation.com/t/help-needed-populating-dropdown-with-string-array/98689>\
**Category:** Ignition\
**Tags:** ignition81, perspective\
**Created:** [November 15, 2024, 9:25pm UTC](https://forum.inductiveautomation.com/t/help-needed-populating-dropdown-with-string-array/98689 "2024-11-15T21:25:20Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ryan\_Crawford](https://avatars.discourse-cdn.com/v4/letter/r/a587f6/32.png) [@Ryan\_Crawford](https://forum.inductiveautomation.com/u/Ryan_Crawford)\
**Post date:** [November 15, 2024, 9:25pm UTC](https://forum.inductiveautomation.com/t/help-needed-populating-dropdown-with-string-array/98689/1 "2024-11-15T21:25:21Z")

</div>

Good Afternoon,

I am seeking some help with getting a string array to populate as options in a dropdown. I have everything going to the string array nicely. I did put a transformation in place and bound it to the options with a property tag to read the string array, but it keeps coming up as blank. I am using a dropdown in perspective.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/0/6/0610c3c4a27a42bd917a95672fa4f85eed0e847f.png)

I am after this (as an example), apologies for the handwriting:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/7/0/702cd327c4776fec80584236aba5e485e2aa3824.jpeg)

```python
# Ensure value is a list from the bound tag
batch_numbers = value if isinstance(value, list) else []

# Initialize an empty list for dropdown options
dropdown_options = []

# Add values from the array to the dropdown options, ensuring no duplicates
for batch_number in batch_numbers:
    if batch_number and batch_number not in [opt["value"] for opt in dropdown_options]:
        dropdown_options.append({"value": str(batch_number), "label": str(batch_number)})

# Return the options list
return dropdown_options

```

Any help would be great.

Thanks,

---

<div class="post-metadata">

**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\
**Post date:** [November 15, 2024, 9:44pm UTC](https://forum.inductiveautomation.com/t/help-needed-populating-dropdown-with-string-array/98689/2 "2024-11-15T21:44:12Z")

</div>

You are running into a type issue. If you put `return isinstance(value, list)` as your first line, you'll see that it returns false. Because of that, your script is falling back to the empty list as the value of `batch_numbers`.

The reported type of the value when bound to a custom array property is a [JsonifiableArrayList](https://files.inductiveautomation.com/sdk/javadoc/ignition81/8.1.25/com/inductiveautomation/perspective/gateway/script/JsonifiableArrayList.html).

You would need to change the first two lines of your transform script to:

```python
	import java.util.ArrayList
	# Ensure value is a list from the bound tag
	batch_numbers = value if isinstance(value, java.util.ArrayList) else []

```

Your attempt at skipping duplicates will not work as you expect, as you are comparing an integer to strings, and that will always not match. You need to cast the `batch_number` to a string when making the check. Your duplicate check should be:

```python
if batch_number and str(batch_number) not in [opt["value"] for opt in dropdown_options]:

```

With the above notes, here is your corrected script:

```python
def transform(self, value, quality, timestamp):
	""" """
	import java.util.ArrayList
	# Ensure value is a list from the bound tag
	batch_numbers = value if isinstance(value, java.util.ArrayList) else []

	# Initialize an empty list for dropdown options
	dropdown_options = []

	# Add values from the array to the dropdown options, ensuring no duplicates
	for batch_number in batch_numbers:
		if batch_number and str(batch_number) not in [opt["value"] for opt in dropdown_options]:
			dropdown_options.append({"value": str(batch_number), "label": str(batch_number)})

	# Return the options list
	return dropdown_options

```

---

<div class="post-metadata">

**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:** [November 15, 2024, 11:03pm UTC](https://forum.inductiveautomation.com/t/help-needed-populating-dropdown-with-string-array/98689/3 "2024-11-15T23:03:58Z")

</div>

No need for any explicit type comparison; the only meaningful thing to defend against is "null", which you can do with a simple coalesce via `or`.

The 'duplicate' detection is also trivial by converting to a set.

Put together with a list comprehension, you can write this as tersely as:

```python
def transform(self, value, quality, timestamp):
	batch_numbers = value or []

	return [
		{
			"value": batch_number,
			"label": batch_number
		}
		for batch_number in sorted(set(batch_numbers))
	]

```

Or in the imperative style:

```python
def transform(self, value, quality, timestamp):
	batch_numbers = value or []
	
	dropdown_options = []

	distinct_batch_numbers = set(batch_numbers)
	sorted_batch_numbers = sorted(distinct_batch_numbers)
	
	for batch_number in sorted_batch_numbers:
		dropdown_options.append({
			"value": batch_number,
			"label": batch_number
		})

	return dropdown_options

```