cascade is a macro library for Rust that makes it easy and ergonomic
to use cascade-like expressions, similar to Dart.
#[macro_use]
extern crate cascade;
fn main() {
let cascaded_list = cascade! {
Vec::new();
..push("Cascades");
..push("reduce");
..push("boilerplate");
};
println!("{:?}", cascaded_list); // 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:
#[macro_use]
extern crate cascade;
#[derive(Clone, Debug)]
struct Person {
pub name: String,
pub age: u32,
pub height: u32,
pub friend_names: Vec<String>
}
fn main() {
// Without cascades
let person = Person {
name: "John Smith",
age: 17,
height: 68, // 5' 8"
friend_names: {
let mut tmp_names = Vec::new();
tmp_names.push("James Smith".to_string());
tmp_names.push("Bob Jones".to_string());
tmp_names.push("Billy Jones".to_string());
tmp_names
}
};
// With cascades
let person = Person {
name: "John Smith",
age: 17,
height: 68,
friend_names: cascade! {
Vec::new();
..push("James Smith".to_string());
..push("Bob Jones".to_string());
..push("Billy Jones".to_string());
}
};
// Cascades also let you do cool stuff like this
let person_one_year_later = 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
letsyntax. This makes it more in-line with Rust syntax and also allows you to specify the type of a cascaded expression.
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.
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:
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:
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:
fn chain_example() {
cascade! {
FnChainTest::new();
..chain().chain().chain();
}
}Written by Jane Lewis