ruda_dataset/transform/
mapper.rs

1use crate::Dataset;
2use std::marker::PhantomData;
3
4/// Basic mapper trait to be used with the [mapper dataset](MapperDataset).
5pub trait Mapper<I, O>: Send + Sync {
6    /// Maps an item of type I to an item of type O.
7    fn map(&self, item: &I) -> O;
8}
9
10/// Dataset mapping each element in an inner dataset to another element type lazily.
11#[derive(new)]
12pub struct MapperDataset<D, M, I> {
13    dataset: D,
14    mapper: M,
15    input: PhantomData<I>,
16}
17
18impl<D, M, I, O> Dataset<O> for MapperDataset<D, M, I>
19where
20    D: Dataset<I>,
21    M: Mapper<I, O> + Send + Sync,
22    I: Send + Sync,
23    O: Send + Sync,
24{
25    fn get(&self, index: usize) -> Option<O> {
26        let item = self.dataset.get(index);
27        item.map(|item| self.mapper.map(&item))
28    }
29
30    fn get_many(&self, indices: &[usize]) -> Option<Vec<O>> {
31        let items = self.dataset.get_many(indices)?;
32        if items.len() != indices.len() {
33            return None;
34        }
35        Some(items.iter().map(|item| self.mapper.map(item)).collect())
36    }
37
38    fn len(&self) -> usize {
39        self.dataset.len()
40    }
41}
42
43#[cfg(test)]
44mod tests {
45    use super::*;
46    use crate::{InMemDataset, test_data};
47
48    #[test]
49    pub fn given_mapper_dataset_when_iterate_should_iterate_though_all_map_items() {
50        struct StringToFirstChar;
51
52        impl Mapper<String, String> for StringToFirstChar {
53            fn map(&self, item: &String) -> String {
54                let mut item = item.clone();
55                item.truncate(1);
56                item
57            }
58        }
59
60        let items_original = test_data::string_items();
61        let dataset = InMemDataset::new(items_original);
62        let dataset = MapperDataset::new(dataset, StringToFirstChar);
63
64        let items: Vec<String> = dataset.iter().collect();
65
66        assert_eq!(vec!["1", "2", "3", "4"], items);
67    }
68}
ruda_dataset/transform/mapper.rs

ruda_dataset/transform/
mapper.rs
