4 releases
0.2.1 | Oct 20, 2023 |
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0.2.0 | Sep 24, 2023 |
0.1.1 | Sep 24, 2023 |
0.1.0 | Sep 24, 2023 |
#392 in Configuration
15KB
274 lines
This is a helper library which is dedicated to make extracting value from environment variables easy.
How To Import
add below line to cargo.toml which is in your project
nb-from-env = "*"
Usage
use nb_from_env::{FromEnv, FromEnvDerive}
#[derive(FromEnvDerive)]
struct MyServerConfig {
log_level: Option<String>,
listen_address: String,
max_conns: i32,
is_debug: bool,
}
fn main() {
dotenv::dotenv().ok();
let config = MyServerConfig::from_env();
...
}
Support Data Types
almost all of primitive types in rust are supported, include:
- String
- i8
- i16
- i32
- i64
- i128
- u8
- u16
- u32
- u64
- u128
- usize
- isize
- bool
- f32
- f64
- Option<T: FromEnv>
you can also implement FromEnv
for your type
Environment Variable Name
If not specified, all environment variables name is the upper-case of field name:
#[derive(FromEnvDerive)]
struct MyConfig {
my_var: String // this will search for MY_VAR in environment varialbes
}
but you can use #[env_var]
tag to specify which environment variable is related to the field:
#[derive(FromEnvDerive)]
struct MyConfig {
#[env_var(THE_REAL_NAME)] // this will search for THE_REAL_NAME in environment variables
my_var: String
}
Default Value
You can specify default value for non-existing environment variable by #[env_default]
tag:
struct MyConfig {
#[env_default("my default value")] // if MY_VAR not exists, "my default value" will assign to my_var
my_var: String
}
note that, the type of default value must be string, value will be convert to correspond type in from_env
function
Optional Type Field
When environment variable whic you expected does not exist, from_env
will panic if correspond field is not optional(i.e Option<T>
). Optional field will be None
if environment variable is not exists
Dependencies
~240–680KB
~16K SLoC