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Allow creation of String arrays from &Option<&str> iterators #680

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merged 2 commits into from
Aug 12, 2021
Merged

Allow creation of String arrays from &Option<&str> iterators #680

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d72966e
Allow creation of String arrays from &Option<&str> iterators
koomen Aug 8, 2021
866ced1
Add links in doc comments
alamb Aug 12, 2021
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32 changes: 27 additions & 5 deletions arrow/src/array/array_string.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -196,11 +196,26 @@ impl<OffsetSize: StringOffsetSizeTrait> GenericStringArray<OffsetSize> {
}
}

impl<'a, Ptr, OffsetSize: StringOffsetSizeTrait> FromIterator<&'a Option<Ptr>>
for GenericStringArray<OffsetSize>
where
Ptr: AsRef<str> + 'a,
{
/// Creates a [`GenericStringArray`] based on an iterator of `Option` references.
fn from_iter<I: IntoIterator<Item = &'a Option<Ptr>>>(iter: I) -> Self {
// Convert each owned Ptr into &str and wrap in an owned `Option`
let iter = iter.into_iter().map(|o| o.as_ref().map(|p| p.as_ref()));
// Build a `GenericStringArray` with the resulting iterator
iter.collect::<GenericStringArray<OffsetSize>>()
}
}

impl<'a, Ptr, OffsetSize: StringOffsetSizeTrait> FromIterator<Option<Ptr>>
for GenericStringArray<OffsetSize>
where
Ptr: AsRef<str>,
{
/// Creates a [`GenericStringArray`] based on an iterator of `Option`s
fn from_iter<I: IntoIterator<Item = Option<Ptr>>>(iter: I) -> Self {
let iter = iter.into_iter();
let (_, data_len) = iter.size_hint();
Expand Down Expand Up @@ -358,6 +373,7 @@ impl<T: StringOffsetSizeTrait> From<GenericListArray<T>> for GenericStringArray<

#[cfg(test)]
mod tests {

use crate::array::{ListBuilder, StringBuilder};

use super::*;
Expand Down Expand Up @@ -484,17 +500,23 @@ mod tests {

#[test]
fn test_string_array_from_iter() {
let data = vec![Some("hello"), None, Some("arrow")];
let data = [Some("hello"), None, Some("arrow")];
let data_vec = data.to_vec();
// from Vec<Option<&str>>
let array1 = StringArray::from(data.clone());
let array1 = StringArray::from(data_vec.clone());
// from Iterator<Option<&str>>
let array2: StringArray = data.clone().into_iter().collect();
let array2: StringArray = data_vec.clone().into_iter().collect();
// from Iterator<Option<String>>
let array3: StringArray =
data.into_iter().map(|x| x.map(|s| s.to_string())).collect();
let array3: StringArray = data_vec
.into_iter()
.map(|x| x.map(|s| s.to_string()))
.collect();
// from Iterator<&Option<&str>>
let array4: StringArray = data.iter().collect::<StringArray>();

assert_eq!(array1, array2);
assert_eq!(array2, array3);
assert_eq!(array3, array4);
}

#[test]
Expand Down