2 releases
0.1.8 | Nov 25, 2019 |
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0.1.7 | Nov 25, 2019 |
#40 in #iter
27KB
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Arraygen
This crate provides Arraygen
derive macro for structs, which generates methods returning arrays filled with the selected struct fields.
Complete example:
#[derive(Arraygen, Debug)]
#[gen_array(fn get_names: &mut String)]
struct Person {
#[in_array(get_names)]
first_name: String,
#[in_array(get_names)]
last_name: String,
}
let mut person = Person {
first_name: "Ada".into(),
last_name: "Lovelace".into()
};
for name in person.get_names().iter_mut() {
**name = name.to_lowercase();
}
assert_eq!(
format!("{:?}", person),
"Person { first_name: \"ada\", last_name: \"lovelace\" }"
);
// PASSES !
// Notice how it was not lowercased on type definition
// but now it is.
As you can see above, the gen_array
attribute generates a new method returning an array of the indicated type. And the in_array
attribute tells which fields are contained within the array returned by that method.
What Arraygen
does under the hood is simply generating the following impl:
impl Person {
#[inline(always)]
fn get_names(&mut self) -> [&mut String; 2] {
[&mut self.first_name, &mut self.last_name]
}
}
The attribute gen_array
For generating an Arraygen
method you have to use the attribute gen_array
on top of the struct, indicating the method name and the return type.
#[derive(Arraygen)]
#[gen_array(fn get_strings: &String]
struct Foo {...}
In the code above, the struct Foo
would have a new method with the following signature: fn get_strings(&self) -> [&Strings; ?] {...}
.
The attribute in_array
In order to fill your Arraygen
methods with struct fields, you have to use the attribute in_array
in each struct field you want to include.
// inside a struct
#[in_array(get_strings)]
name: String,
#[in_array(get_strings)]
id: String,
You have to match the method name used in gen_array
and in in_array
in order to include those fields in the generated method.
Documentation
For more information, check the documentation page.
Limitations
There are not particular limitations, really. You can use this derive to return Copy objects, Trait objects, and basically any kind of object that can be a struct member.
Also, notice that there are no dynamic memory allocations involved.
The only drawback would be a little impact in compilation times.
About the Syntax
I'm open to change the syntax for the 1.0 version. Participate in the issue Syntax Proposals to give your opinion on this matter.
GettersByType
This crate is heavily inspired by GettersByType which is another derive that allows you to do the same thing. But that one is more opinionated, less flexible and less powerful, with the only advantage of being less verbose. That's why I decided to work on this new solution.
License
MIT
Dependencies
~1.5MB
~37K SLoC