# thisisplural
[](https://github.com/ryo33/thisisplural)
[](https://crates.io/crates/thisisplural)
[](https://docs.rs/thisisplural)
`#[derive(Plural)]` for creating frictionless new types with any collection
type.
## Features
- Automatically implements `From`, `Into`, `FromIterator`, `IntoIterator`, and
methods like `.len()` or `::with_capacity`.
- Supports any collection that behaves like `Vec` and `HashMap`.
## Example
```rust
// This implements `From`, `Into`, `FromIterator`, `IntoIterator`.
#[derive(Plural)]
struct Numbers(Vec<u32>);
// use `From` trait
let my_favorite_numbers: Numbers = vec![].into();
// methods like `len()` are implemented
assert_eq!(my_favorite_numbers.len(), 0);
assert!(my_favorite_numbers.is_empty());
// `FromIterator` allows this `collect()`
let doubled_numbers: Numbers = my_favorite_numbers.iter().map(|x| x * 2).collect();
// `HashMap` like collections are also supported
#[derive(Plural)]
struct FavoriteNumbers(HashMap<&'static str, Numbers>);
// construct the struct with using `FromIterator`
let favorite_numbers =
FavoriteNumbers::from_iter([("ryo33", my_favorite_numbers), ("someone", doubled_numbers)]);
// use it in a `for` loop (`IntoIterator` trait)
for (name, numbers) in favorite_numbers {
// use Deref trait
println!("{} has {} favorite number(s)", name, numbers.0.len());
}
```
## Selective Implementation with `#[plural(...)]`
By default, `#[derive(Plural)]` implements a comprehensive set of methods and traits. However, you can gain finer-grained control over what gets generated by using the `#[plural(...)]` attribute.
If you specify methods or traits within the `plural` attribute, only those specified will be implemented.
**Available options for `#[plural(...)]`:**
- `len`: Implements `fn len(&self) -> usize`.
- `is_empty`: Implements `fn is_empty(&self) -> bool`.
- `iter`: Implements `fn iter(&self) -> impl Iterator<Item = &ItemType>`.
- `capacity`: Implements `fn capacity(&self) -> usize`.
- `reserve`: Implements `fn reserve(&mut self, additional: usize)`.
- `with_capacity`: Implements `fn with_capacity(capacity: usize) -> Self`.
- `new`: Implements `fn new() -> Self`.
- `clear`: Implements `fn clear(&mut self)`.
- `extend`: Implements `impl Extend<ItemType> for Self`.
- `from_plural`: Implements `impl From<Self> for UnderlyingCollectionType`.
- `from_inner`: Implements `impl From<UnderlyingCollectionType> for Self`.
- `into_iter`: Implements `impl IntoIterator for Self` (consuming `self`).
- `into_iter_ref`: Implements `impl IntoIterator for &Self`.
- `from_iter`: Implements `impl FromIterator<ItemType> for Self`.
**Example of selective implementation:**
```rust
use thisisplural::Plural;
use std::collections::VecDeque;
// Only implement `new`, `len`, and the `Extend` trait.
#[derive(Plural, Debug, PartialEq)]
#[plural(new, len, extend)]
struct MyQueue(VecDeque<String>);
fn main() {
let mut queue = MyQueue::new();
assert_eq!(queue.len(), 0);
queue.extend(vec!["hello".to_string(), "world".to_string()]);
assert_eq!(queue.len(), 2);
}
```