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new 2b40d1dfc3 [Variant] Add Variant::as_object and Variant::as_list
(#7755)
2b40d1dfc3 is described below
commit 2b40d1dfc35862ff350a40dfbc66f8a14f4eea31
Author: Andrew Lamb <[email protected]>
AuthorDate: Tue Jun 24 07:26:36 2025 -0400
[Variant] Add Variant::as_object and Variant::as_list (#7755)
# Which issue does this PR close?
- part of https://github.com/apache/arrow-rs/issues/6736
# Rationale for this change
- While reviewing @friendlymatthew 's PR
https://github.com/apache/arrow-rs/pull/7740 I found that the code to
get the Variant object was awkward
I think that an accessor is similar to the existing `as_null`, `as_i32,`
etc APIs.
# What changes are included in this PR?
1. Add Variant::as_object and Variant::as_list
# Are there any user-facing changes?
New API (and docs with tests)
---
parquet-variant/src/variant.rs | 64 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 64 insertions(+)
diff --git a/parquet-variant/src/variant.rs b/parquet-variant/src/variant.rs
index 2e042b6074..51327b4d25 100644
--- a/parquet-variant/src/variant.rs
+++ b/parquet-variant/src/variant.rs
@@ -809,6 +809,70 @@ impl<'m, 'v> Variant<'m, 'v> {
}
}
+ /// Converts this variant to an `Object` if it is an [`VariantObject`].
+ ///
+ /// Returns `Some(&VariantObject)` for object variants,
+ /// `None` for non-object variants.
+ ///
+ /// # Examples
+ /// ```
+ /// # use parquet_variant::{Variant, VariantBuilder, VariantObject};
+ /// # let (metadata, value) = {
+ /// # let mut builder = VariantBuilder::new();
+ /// # let mut obj = builder.new_object();
+ /// # obj.append_value("name", "John");
+ /// # obj.finish();
+ /// # builder.finish()
+ /// # };
+ /// // object that is {"name": "John"}
+ /// let variant = Variant::try_new(&metadata, &value).unwrap();
+ /// // use the `as_object` method to access the object
+ /// let obj = variant.as_object().expect("variant should be an object");
+ /// assert_eq!(obj.field_by_name("name").unwrap(),
Some(Variant::from("John")));
+ /// ```
+ pub fn as_object(&'m self) -> Option<&'m VariantObject<'m, 'v>> {
+ if let Variant::Object(obj) = self {
+ Some(obj)
+ } else {
+ None
+ }
+ }
+
+ /// Converts this variant to a `List` if it is a [`VariantList`].
+ ///
+ /// Returns `Some(&VariantList)` for list variants,
+ /// `None` for non-list variants.
+ ///
+ /// # Examples
+ /// ```
+ /// # use parquet_variant::{Variant, VariantBuilder, VariantList};
+ /// # let (metadata, value) = {
+ /// # let mut builder = VariantBuilder::new();
+ /// # let mut list = builder.new_list();
+ /// # list.append_value("John");
+ /// # list.append_value("Doe");
+ /// # list.finish();
+ /// # builder.finish()
+ /// # };
+ /// // list that is ["John", "Doe"]
+ /// let variant = Variant::try_new(&metadata, &value).unwrap();
+ /// // use the `as_list` method to access the list
+ /// let list = variant.as_list().expect("variant should be a list");
+ /// assert_eq!(list.len(), 2);
+ /// assert_eq!(list.get(0).unwrap(), Variant::from("John"));
+ /// assert_eq!(list.get(1).unwrap(), Variant::from("Doe"));
+ /// ```
+ pub fn as_list(&'m self) -> Option<&'m VariantList<'m, 'v>> {
+ if let Variant::List(list) = self {
+ Some(list)
+ } else {
+ None
+ }
+ }
+
+ /// Return the metadata associated with this variant, if any.
+ ///
+ /// Returns `Some(&VariantMetadata)` for object and list variants,
pub fn metadata(&self) -> Option<&'m VariantMetadata> {
match self {
Variant::Object(VariantObject { metadata, .. })
