tustvold commented on code in PR #3912:
URL: https://github.com/apache/arrow-rs/pull/3912#discussion_r1146128716
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arrow-array/src/cast.rs:
##########
@@ -709,6 +709,165 @@ where
T::from(array.to_data())
}
+mod private {
+ pub trait Sealed {}
+}
+
+/// An extension trait for `dyn Array` that provides ergonomic downcasting
+///
+/// ```
+/// # use std::sync::Arc;
+/// # use arrow_array::{ArrayRef, Int32Array};
+/// # use arrow_array::cast::AsArray;
+/// # use arrow_array::types::Int32Type;
+/// let col = Arc::new(Int32Array::from(vec![1, 2, 3])) as ArrayRef;
+/// assert_eq!(col.as_primitive::<Int32Type>().values(), &[1, 2, 3]);
+/// ```
+pub trait AsArray: private::Sealed {
+ /// Downcast this to a [`BooleanArray`] returning `None` if not possible
+ fn as_boolean_opt(&self) -> Option<&BooleanArray>;
+
+ /// Downcast this to a [`BooleanArray`] panicking if not possible
+ fn as_boolean(&self) -> &BooleanArray {
+ self.as_boolean_opt().expect("boolean array")
+ }
+
+ /// Downcast this to a [`PrimitiveArray`] returning `None` if not possible
+ fn as_primitive_opt<T: ArrowPrimitiveType>(&self) ->
Option<&PrimitiveArray<T>>;
+
+ /// Downcast this to a [`PrimitiveArray`] panicking if not possible
+ fn as_primitive<T: ArrowPrimitiveType>(&self) -> &PrimitiveArray<T> {
+ self.as_primitive_opt().expect("primitive array")
+ }
+
+ /// Downcast this to a [`GenericByteArray`] returning `None` if not
possible
+ fn as_bytes_opt<T: ByteArrayType>(&self) -> Option<&GenericByteArray<T>>;
Review Comment:
In hindsight I probably should have called this `GenericBytesArray` but hey
ho
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