lowdash/
first_or_empty.rs

1use crate::first::first;
2
3/// Returns the first item from the collection.
4/// If the collection is empty, returns the default value of `T`.
5///
6/// # Arguments
7/// * `collection` - A slice of items.
8///
9/// # Returns
10/// * `T` - The first item in the collection.
11///         If the collection is empty, returns `T::default()`.
12///
13/// # Examples
14/// ```rust
15/// use lowdash::first_or_empty;
16///
17/// let numbers = vec![1, 2, 3];
18/// let first_num = first_or_empty(&numbers);
19/// assert_eq!(first_num, 1);
20///
21/// let empty: Vec<i32> = vec![];
22/// let first_num = first_or_empty(&empty);
23/// assert_eq!(first_num, 0); // i32::default() is 0
24/// ```
25///
26/// ```rust
27/// use lowdash::first_or_empty;
28///
29/// #[derive(Debug, PartialEq, Clone, Default)]
30/// struct Person {
31///     name: String,
32///     age: u32,
33/// }
34///
35/// let people = vec![
36///     Person { name: "Alice".to_string(), age: 25 },
37///     Person { name: "Bob".to_string(), age: 30 },
38/// ];
39///
40/// let first_person = first_or_empty(&people);
41/// assert_eq!(first_person, Person { name: "Alice".to_string(), age: 25 });
42///
43/// let empty_people: Vec<Person> = vec![];
44/// let first_person = first_or_empty(&empty_people);
45/// assert_eq!(first_person, Person::default());
46/// ```
47pub fn first_or_empty<T>(collection: &[T]) -> T
48where
49    T: Clone + Default,
50{
51    let (item, _) = first(collection);
52    item
53}
54
55#[cfg(test)]
56mod tests {
57    use super::*;
58
59    #[derive(Debug, PartialEq, Clone, Default)]
60    struct Item {
61        name: String,
62        value: i32,
63    }
64
65    #[test]
66    fn test_first_or_empty_with_non_empty_collection() {
67        let collection = vec![1, 2, 3];
68        let first = first_or_empty(&collection);
69        assert_eq!(first, 1);
70    }
71
72    #[test]
73    fn test_first_or_empty_with_empty_collection() {
74        let collection: Vec<i32> = vec![];
75        let first = first_or_empty(&collection);
76        assert_eq!(first, 0); // i32::default() is 0
77    }
78
79    #[test]
80    fn test_first_or_empty_with_structs() {
81        let item1 = Item {
82            name: "Item1".to_string(),
83            value: 10,
84        };
85        let item2 = Item {
86            name: "Item2".to_string(),
87            value: 20,
88        };
89        let collection = vec![item1.clone(), item2.clone()];
90        let first = first_or_empty(&collection);
91        assert_eq!(first, item1);
92    }
93
94    #[test]
95    fn test_first_or_empty_with_single_item() {
96        let collection = vec![42];
97        let first = first_or_empty(&collection);
98        assert_eq!(first, 42);
99    }
100
101    #[test]
102    fn test_first_or_empty_with_custom_default() {
103        let collection: Vec<Item> = vec![];
104        let first = first_or_empty(&collection);
105        assert_eq!(first, Item::default());
106    }
107
108    #[test]
109    fn test_first_or_empty_with_partial_empty_struct() {
110        let item = Item {
111            name: "Partial".to_string(),
112            value: 0,
113        };
114        let collection = vec![item.clone()];
115        let first = first_or_empty(&collection);
116        assert_eq!(first, item);
117    }
118}
lowdash/first_or_empty.rs

lowdash/
first_or_empty.rs
