# vtkStringArray not being stored correctly in CellData for vtkPolyData object
**URL:** https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805
**Category:** Support
**Created:** [February 26, 2023, 12:41am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805 "2023-02-26T00:41:57Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Robert\_Collar](https://discourse.vtk.org/u/Robert_Collar)
#### Post date: [February 26, 2023, 12:41am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805/1 "2023-02-26T00:41:57Z")
Hi VTK community,
In the example below, a simple `vtkPolyData` object is constructed and two arrays — one numerical and another of strings — is passed to its cells. Upon subsequently retrieving the arrays, only the numerical one has any data in it (printing the string array results in `None`). Does anyone know why this is happening and how I might resolve the issue?
Best, Robert Collar
```python
import vtk
import vtk.util.numpy_support as vtknumpy
points = vtk.vtkPoints()
points.SetNumberOfPoints(4)
line = vtk.vtkLine()
lines = vtk.vtkCellArray()
# create first line segment
points.SetPoint(0, 0, 0, 0)
line.GetPointIds().SetId(0, 0)
points.SetPoint(1, 1, 1, 1)
line.GetPointIds().SetId(1, 1)
lines.InsertNextCell(line)
# create second line segment
points.SetPoint(2, 1, 1, 1)
line.GetPointIds().SetId(0, 2)
points.SetPoint(3, 2, 2, 2)
line.GetPointIds().SetId(1, 3)
lines.InsertNextCell(line)
linesPolyData = vtk.vtkPolyData()
linesPolyData.SetPoints(points)
linesPolyData.SetLines(lines)
num_ids = vtknumpy.numpy_to_vtk([0,1]) # TODO: change to be a function of number of lines
num_ids.SetName("num id")
num_ids.SetNumberOfComponents(1)
linesPolyData.GetCellData().AddArray(num_ids)
str_ids = vtk.vtkStringArray()
str_ids.SetNumberOfValues(2)
str_ids.InsertValue(0, "a")
str_ids.InsertValue(1, "b")
str_ids.SetName("str id")
str_ids.SetNumberOfComponents(1)
linesPolyData.GetCellData().AddArray(str_ids)
print(linesPolyData.GetCellData().GetArray("num id"))
print(linesPolyData.GetCellData().GetArray("str id"))
```
---
### Author:  [@toddy](https://discourse.vtk.org/u/toddy)
#### Post date: [February 26, 2023, 3:26am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805/2 "2023-02-26T03:26:50Z")
Perhaps `str_ids.SetNumberOfComponents(1)`
---
### Author:  [@Robert\_Collar](https://discourse.vtk.org/u/Robert_Collar)
#### Post date: [February 26, 2023, 3:45am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805/3 "2023-02-26T03:45:34Z")
Hi Todd, thanks for the suggestion, though adding that unfortunately doesn’t solve the problem. For future viewers, I’ve edited my initial post to include that line!
---
### Author:  [@dgobbi](https://discourse.vtk.org/u/dgobbi)
#### Post date: [February 26, 2023, 4:40am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805/4 "2023-02-26T04:40:08Z")
Use `GetAbstractArray()`.
The `GetArray()` is restricted to numerical data, it can only return subclasses of `vtkDataArray`. For everything else it returns NULL
So a `vtkStringArray` must be added with `AddArray()`, but retrieved with `GetAbstractArray()`.
---
### Author:  [@Robert\_Collar](https://discourse.vtk.org/u/Robert_Collar)
#### Post date: [February 26, 2023, 4:52am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805/5 "2023-02-26T04:52:09Z")
This worked, thanks @dgobbi!
---
### Author:  [@toddy](https://discourse.vtk.org/u/toddy)
#### Post date: [February 27, 2023, 12:27am UTC](https://discourse.vtk.org/t/vtkstringarray-not-being-stored-correctly-in-celldata-for-vtkpolydata-object/10805/6 "2023-02-27T00:27:43Z")
That’s intuitive. 🤔