#cute #default

macro cute_custom_default

Derive macro for Default trait with customization

2 stable releases

2.1.0 Mar 21, 2020
2.0.0 Apr 6, 2019
1.0.0 Apr 6, 2019
Download history 63/week @ 2023-07-19 78/week @ 2023-07-26 33/week @ 2023-08-02 69/week @ 2023-08-09 57/week @ 2023-08-16 41/week @ 2023-08-23 66/week @ 2023-08-30 94/week @ 2023-09-06 73/week @ 2023-09-13 37/week @ 2023-09-20 45/week @ 2023-09-27 39/week @ 2023-10-04 55/week @ 2023-10-11 120/week @ 2023-10-18 79/week @ 2023-10-25 89/week @ 2023-11-01

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Apache-2.0

16KB
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CustomDefault

Build Crates.io Documentation

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

~1.5MB
~32K SLoC