I have an enum with two variants:
enum DatabaseType {
Memory,
RocksDB,
}
What do I need in order to make a conditional if inside a function that checks if an argument is DatabaseType::Memory
or DatabaseType::RocksDB
?
fn initialize(datastore: DatabaseType) -> Result<V, E> {
if /* Memory */ {
//..........
} else if /* RocksDB */ {
//..........
}
}
First, go back and re-read the free, official Rust book : The Rust Programming Language , specifically the chapter on enums .
match
fn initialize(datastore: DatabaseType) {
match datastore {
DatabaseType::Memory => {
// ...
}
DatabaseType::RocksDB => {
// ...
}
}
}
if let
fn initialize(datastore: DatabaseType) {
if let DatabaseType::Memory = datastore {
// ...
} else {
// ...
}
}
==
#[derive(PartialEq)]
enum DatabaseType {
Memory,
RocksDB,
}
fn initialize(datastore: DatabaseType) {
if DatabaseType::Memory == datastore {
// ...
} else {
// ...
}
}
See also:
// A simple example that runs in rust 1.58:
enum Aap {
Noot(i32, char),
Mies(String, f64),
}
fn main() {
let aap: Aap = Aap::Noot(42, 'q');
let noot: Aap = Aap::Mies(String::from("noot"), 422.0);
println!("{}", doe(aap));
println!("{}", doe(noot));
}
fn doe(a: Aap) -> i32 {
match a {
Aap::Noot(i, _) => i,
Aap::Mies(_, f) => f as i32,
}
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.