3 stable releases
2.2.0 | Aug 10, 2024 |
---|---|
2.1.0 | Mar 21, 2020 |
2.0.0 | Apr 6, 2019 |
1.0.0 |
|
#2007 in Procedural macros
176 downloads per month
17KB
204 lines
CustomDefault
Derive macro for Default
trait with customization
lib.rs
:
CustomDefault
Provides derive macro for Default
trait with customization point
Attributes
def_val=<value>
- Specifies default value for field. Panics on incorrect type of field.def_exp="expression"
- Specifies expression to be placed as initializer to field. No pre-processing.
Usage
use cute_custom_default::CustomDefault;
pub fn default_value_string() -> &'static str {
"default_value_string"
}
#[derive(CustomDefault)]
pub struct MyStruct {
#[def_val='c']
pub custom_char: char,
#[def_val=b"my_bytes"]
pub custom_bytes: [u8; 8],
#[def_val=b"my_bytes"]
pub custom_bytes_slice: &'static [u8],
#[def_val=b'b']
pub custom_default: u8,
#[def_val=true]
pub custom_bool: bool,
pub normal_bool: bool,
#[def_exp="\"Just my string\".to_owned()"]
pub expression: String,
#[def_exp="default_value_string()"]
pub static_str: &'static str,
#[def_val="Just my string"]
pub string: String,
#[def_val="Just my string"]
pub static_str_again: &'static str,
#[def_val=666]
pub u32_field: u32,
#[def_exp="std::u16::MAX"]
pub u16_field: u16,
#[def_exp="-655_555"]
pub i32_field: i32,
}
fn main() {
let my_struct = MyStruct::default();
assert_eq!(my_struct.custom_char, 'c');
assert_eq!(my_struct.custom_default, b'b');
assert_eq!(&my_struct.custom_bytes, b"my_bytes");
assert_eq!(my_struct.custom_bytes_slice, b"my_bytes");
assert_eq!(my_struct.custom_bool, true);
assert_eq!(my_struct.normal_bool, false);
assert_eq!(my_struct.expression, "Just my string");
assert_eq!(my_struct.static_str, default_value_string());
assert_eq!(my_struct.string, "Just my string");
assert_eq!(my_struct.static_str_again, "Just my string");
assert_eq!(my_struct.u32_field, 666);
assert_eq!(my_struct.u16_field, std::u16::MAX);
assert_eq!(my_struct.i32_field, -655_555);
}
Dependencies
~225–670KB
~16K SLoC