cascade: Cascade expressions in Rust!cascade is a macro library for Rust that makes it easy and ergonomic
to use cascade-like expressions, similar to Dart.
```rust
extern crate cascade;
fn main() { let cascadedlist = cascade! { Vec::new(); ..push("Cascades"); ..push("reduce"); ..push("boilerplate"); }; println!("{:?}", cascadedlist); // Will print '["Cascades", "reduce", "boilerplate"]' } ```
This is only a small example of what cascade lets you do:
the basic_cascades example in this repository covers the other
cool features of the cascade! macro.
Cascades reduce boilerplate by eliminating the need for a 'temporary' variable when making several method calls in a row, and it also helps make struct member assignments look more ergonomic. For example: ```rust
extern crate cascade;
struct Person {
pub name: String,
pub age: u32,
pub height: u32,
pub friend_names: Vec
fn main() { // Without cascades let person = Person { name: "John Smith", age: 17, height: 68, // 5' 8" friendnames: { let mut tmpnames = Vec::new(); tmpnames.push("James Smith".tostring()); tmpnames.push("Bob Jones".tostring()); tmpnames.push("Billy Jones".tostring()); tmpnames } }; // With cascades let person = Person { name: "John Smith", age: 17, height: 68, friendnames: cascade! { Vec::new(); ..push("James Smith".tostring()); ..push("Bob Jones".tostring()); ..push("Billy Jones".tostring()); } }; // Cascades also let you do cool stuff like this let persononeyearlater = cascade! { person; ..age += 1; ..height += 2; }; } ```
In addition, cascades make it easier to design fluent interfaces.
No more returning self with every single function!
1.0.0: cascade has reached 1.0! Here are some of the cool new features and syntax
changes made as a part of this:
- The syntax for binding variables has been changed to use let syntax. This makes it more
in-line with Rust syntax and also allows you to specify the type of a cascaded expression.
rust
cascade! {
// If you don't need to bind the statement to an identifier, you can use _
let _: Vec<u32> = vec![1,2,3].into_iter().map(|x| x + 1).collect();
..push(1);
}
- Statements no longer need | in front of them. You can just put the statement right in there, no prefix needed.
- You can return expressions from cascades, just like normal Rust blocks. By default,
cascades will already return the value of the cascaded variable. But if you want to return
a custom expression, you can put it at the end of a cascade block, with no semicolon.
rust
let has_more_than_three_elements = cascade! {
let v = vec![1,2,3];
..push(4);
v.len() > 3
};
println!("{}", cascade! {
vec![1,2,3];
..push(4);
..into_iter().fold(0, |acc, x| acc + x)
});
- Finally, you can have nested blocks within a cascade block. For example:
rust
cascade! {
vec![1,2,3];
{
let a = 1;
..push(a);
};
}
I hope you enjoy cascade 1.0! Remember to leave any complaints or suggestions
on the issue tracker.
0.1.3: The ? operator now works with cascades, for scenarios like this:
rust
fn file_read() -> Result<SomeFileClass, ErrorMsg> {
cascade! {
SomeFileClass::create_file_reader("test.txt");
..load()?;
..check_validity()?;
}
}
0.1.2: You can now chain methods together, like this:
rust
fn chain_example() {
cascade! {
FnChainTest::new();
..chain().chain().chain();
}
}
Written by Jane Lewis