Adapt version
$ rustc --version
rustc 1.55.0 (c8dfcfe04 2021-09-06)
If you want to overload methods that have different amount of args likes following
// Constructor with 2 args.
fn new(arg0, arg1) -> Self {
...
}
// Constructor with 1 arg.
fn new(arg) -> Self {
...
}
Macro is your better friend.
So macro can be used for pseud-overloading.
Pseud-overloading with macro.
struct SampleStruct {
ip_address: IpAddr,
port_number: u16,
sample_socket: socket2::Socket,
}
macro_rules! SampleStruct_new {
($str_ip:expr , $num_port:expr) => ({
let ip: IpAddr = $str_ip.parse::<IpAddr>()
.unwrap_or_else( |_| { panic!("`address` MUST be an IPv4 address or IPv6 address.") });
SampleStruct {
ip_address: ip,
port_number: $num_port,
sample_socket: Socket::new(
if ip.is_ipv4() { Domain::IPV4 } else { Domain::IPV6 },
Type::DGRAM,
Some(Protocol::UDP)
).unwrap()
}
});
($obj_SocketAddr:expr) => ({
SampleStruct {
ip_address: $obj_SocketAddr.ip(),
port_number: $obj_SocketAddr.port(),
sample_socket: Socket::new(
if $obj_SocketAddr.ip().is_ipv4() { Domain::IPV4 } else { Domain::IPV6 },
Type::DGRAM,
Some(Protocol::UDP)
).unwrap()
}
});
}
Then it uses as following:
fn main() {
let foo = SampleStruct_new!("127.0.0.1", 12345);
println!("IP address = {}, Port = {}", foo.ip_address.to_string(), foo.port_number);
let ipv6_sock_addr = SocketAddr::new("::1".parse::<IpAddr>().unwrap(), 12345);
let bar = SampleStruct_new!(ipv6_sock_addr);
println!("IP address = {}, Port = {}", bar.ip_address.to_string(), bar.port_number);
}
To see a sample code, go Rust playground
Generics with placeholder.
Generics with placeholder is also your frind. _:()
in impl
block means "this is unused argument".
trait SampleTrait<T, O> {
fn new(address:T, port:O) -> SampleStruct;
}
impl SampleTrait<&str, u16> for SampleStruct {
fn new(address: &str, port: u16) -> Self {
let addr = address.to_string().parse::<IpAddr>()
.unwrap_or_else( |_| { panic!("`address` MUST be an IPv4 address (dotted-decimal form) or an IPv6 address.") });
return SampleStruct {
ip_address: addr,
port_number: port,
sample_socket: Socket::new(
if addr.is_ipv4() { Domain::IPV4 } else { Domain::IPV6 },
Type::DGRAM,
Some(Protocol::UDP)
).unwrap()
}
}
}
impl SampleTrait<SocketAddr, ()> for SampleStruct {
fn new(address: SocketAddr, _:()) -> Self {
return SampleStruct {
ip_address: address.ip(),
port_number: address.port(),
sample_socket: Socket::new(
if address.ip().is_ipv4() { Domain::IPV4 } else { Domain:: IPV6 },
Type::DGRAM,
Some(Protocol::UDP)
).unwrap()
}
}
}
When calling fn new(address: SocketAddr, _:())
, the ()
MUST be passed to unused args. So it seems slightly ugly in this way.
fn main() {
let foo = SampleStruct::new("127.0.0.1".to_string(), 12345);
println!("IP address = {}, Port = {}", foo.ip_address.to_string(), foo.port_number);
let ipv6_sock_addr = SocketAddr::new("::1".parse::<IpAddr>().unwrap(), 12345);
let baz = SampleStruct::new(ipv6_sock_addr, ());
println!("IP address = {}, Port = {}", baz.ip_address.to_string(), baz.port_number);
}
To see a sample code, go Rust playground
Top comments (1)
Nice trick!