23 releases
0.3.2 | Jan 31, 2022 |
---|---|
0.3.0 | Jun 17, 2021 |
0.1.14 | Sep 12, 2020 |
0.1.13 | May 21, 2020 |
0.1.11 | Nov 25, 2019 |
#36 in #iter
44KB
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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() {
*name = name.to_lowercase();
}
assert_eq!(
format!("{:?}", person),
"Person { first_name: \"ada\", last_name: \"lovelace\" }"
);
// PASSES !
// Notice how it was not lowercased on object creation
// but now it is.
As you can see above, the gen_array
attribute generates a new method returning an array of the indicated type. Additionally, 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. There you will indicate the method name and the return type. Optionally, you can also indicate the visibility or an implicit_select_all
clause. In the following example you'll see how to tweak the visibility:
#[derive(Arraygen)]
#[gen_array(pub(crate) fn get_strings: &String)]
struct Foo {...}
In the code above, the struct Foo
would have a new method with the following signature:
pub(crate) fn get_strings(&self) -> [&String; ?] {...}
The attribute in_array
:
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)]
id: String,
#[in_array(get_strings, get_names)]
name: String,
You have to match the method name used in gen_array
and in_array
to include these fields in each generated method. So in this example, assuming gen_strings
and get_names
are both generated by gen_array
, the former will get populated with the fields id
and name
, and the latter will get populated with the field name
.
It is also possible to entirely omit the attribute in_array
with the use of an implicit_select_all
clause. Check the "implicit_select_all" section in the documentation to learn more about this possibility.
Generating arrays of Trait Objects:
Trait Objects are fully supported, check the Trait Objects section in the documentation to see a few working examples.
Implicit selection of Fields by their Types
With the clause implicit_select_all
, you may select fields without using in_array
, check this section in the documentation to see an example.
Documentation
For more information, check the documentation page.
Usage
With Cargo, you can add this line to your Cargo.toml:
[dependencies]
arraygen = "0.3.2"
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.
Known Problems
Error messages could be improved in a few cases. And there is no proper support for warnings yet. Arraygen prints standard messages instead of warnings at the moment.
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
~35K SLoC