sgilmore10 opened a new pull request, #37593:
URL: https://github.com/apache/arrow/pull/37593
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### Rationale for this change
We should modify `arrow.type.Type` to inherit from
`matlab.mixin.Heterogeneous` so that it's possible to create a nonscalar array
containing different concrete subclasses of `arrow.type.Type`.
**Example**
```matlab
>> float32Type = arrow.float32();
>> timestampType = arrow.timestamp(TimeZone="Pacific/Fiji");
>> typeArray = [float32Type timestampType]
typeArray =
1×2 heterogeneous FixedWidthType (Float32Type, TimestampType) array with
properties:
ID
```
Currently, running the example above results in an error:
```matlab
>> float32Type = arrow.float32();
>> timestampType = arrow.timestamp(TimeZone="Pacific/Fiji");
>> typeArray = [float32Type timestampType]
Error using horzcat
The following error occurred converting from arrow.type.TimestampType to
arrow.type.Float32Type:
Invalid argument at position 1. Value must be of type
libmexclass.proxy.Proxy or be convertible to libmexclass.proxy.Proxy.
```
### What changes are included in this PR?
1. Updated `arrow.type.Type` to inherit from `matlab.mixin.Heterogeneous`.
Previously, it only inherited from `matlab.mixin.CustomDisplay`.
2. Because `arrow.type.Type` is now `heterogeneous`, its subclasses cannot
override the protected method `getPropertyGroups` - which is inherited from
`matlab.mixin.CustomDisplay`. This method must be `Sealed` and defined on
`Type` because only `Sealed` methods can be called on nonscalar `heterogeneous`
arrays. To get around this limitation, I defined a new abstract template method
called `getDisplayPropertyGroups`, which `getPropertyGroups` invokes if the
array is either scalar or nonscalar and `homogeneous`. Refer to [this
link](https://www.mathworks.com/help/matlab/matlab_oop/custom-display-for-heterogeneous-arrays.html)
for more details.
**Displaying a nonscalar *heterogeneous* `arrow.type.Type`**
```matlab
>> float32Type = arrow.timestamp(TimeUnit="Second");
>> timestampType = arrow.timestamp(TimeZone="Pacific/Fiji");
>> typeArray = [float32Type timestampType]
typeArray =
1×2 heterogeneous FixedWidthType (Float32Type, TimestampType) array with
properties:
ID
```
**Displaying a nonscalar *homogeneous* `arrow.type.Type`**
```matlab
>> timestampType1 = arrow.timestamp(TimeUnit="Second");
>> timestampType2 = arrow.timestamp(TimeZone="Pacific/Fiji");
>> typeArray = [timestampType1 timestampType2]
typeArray =
1×2 TimestampType array with properties:
ID
TimeUnit
TimeZone
```
### Are these changes tested?
Yes
1. Added a new test class in `test/arrow/type` called `tDisplay.m`
2. Added display unit tests for all concrete subclasses of `arrow.type.Type`
if they did not already exists.
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### Are there any user-facing changes?
Yes. Users can now create nonscalar arrays with different concrete
subclasses of `arrow.type.Type`.
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