How do I declare a "static" field in a struct in Rust, preferably with a default value:
struct MyStruct {
x: i32, // instance
y: i32, // instance
my_static: i32 = 123, // static, how?
}
fn main() {
let a = get_value();
if a == MyStruct::my_static {
//...
} else {
//...
}
}
You can declare an associated constant in an impl:
struct MyStruct {
x: i32,
y: i32,
}
impl MyStruct {
const MY_STATIC: i32 = 123;
}
fn main() {
println!("MyStruct::MY_STATIC = {}", MyStruct::MY_STATIC);
}
different things in Rust link
Rust does not support static fields in structures, so you can't do that. The closest thing you can get is an associated method:
struct MyStruct {
x: i32,
y: i32,
}
impl MyStruct {
#[inline]
pub fn my_static() -> i32 {
123
}
}
fn main() {
let a = get_value();
if a == MyStruct::my_static() {
//...
} else {
//...
}
}
static in the module your struct is in, that's it.
You can't declare a field static in a struct.
You can declare a static variable at module scope like this :
static FOO: int = 42;
And you can't have a static variable mutable without unsafe code : to follow borrowing rules it would have to be wrapped in a container making runtime borrowing checks and being Sync, like Mutex or RWLock, but these cannot be stored in static variable as they have non-trivial constructors.
Mutex you can combine it with lazy-static! (which does additional wrapping of its own)