考虑以下示例：
pub enum DigitalWallet {
WithMemo {
currency: String,
address: String,
tag: String,
},
WithoutMemo {
currency: String,
address: String,
},
}
impl<'a> DigitalWallet {
fn getCurrency(self: &'a Self) -> &'a String {
match self {
DigitalWallet::WithMemo {
currency: String, ..
} => currency,
DigitalWallet::WithoutMemo {
currency: String, ..
} => currency,
}
}
}
为什么会导致以下情况？
error[E0425]: cannot find value `currency` in this scope
--> src/lib.rs:18:18
|
18 | } => currency,
| ^^^^^^^^ not found in this scope
error[E0425]: cannot find value `currency` in this scope
--> src/lib.rs:21:18
|
21 | } => currency,
| ^^^^^^^^ not found in this scope
您语法错误。类型永远不会在模式中重复。
字段模式的语法为field_name: binding_name（并且field_name: field_name可以简化为field_name）：
struct Foo {
foo: i32,
}
fn main() {
let foo = Foo { foo: 42 };
match foo {
Foo {
foo: local_name_for_that_foo,
} => {
println!("{}", local_name_for_that_foo);
}
}
}
（永久链接到操场）
因此，您需要
match self {
DigitalWallet::WithMemo { currency, .. } => currency,
DigitalWallet::WithoutMemo { currency, .. } => currency,
}
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我来说两句