[英]How to pattern match a String in a struct against a literal
In my code below I find that the code in match_num_works()
has a certain elegance. 在下面的代码中,我发现
match_num_works()
中的代码具有一定的风格。 I would like to write a String
match with a similar formulation but cannot get it to work. 我想编写一个具有类似公式的
String
匹配项,但无法使其正常工作。 I end up with match_text_works()
which is less elegant. 我最终得到了
match_text_works()
,它不太优雅。
struct FooNum {
number: i32,
}
// Elegant
fn match_num_works(foo_num: &FooNum) {
match foo_num {
&FooNum { number: 1 } => (),
_ => (),
}
}
struct FooText {
text: String,
}
// Clunky
fn match_text_works(foo_text: &FooText) {
match foo_text {
&FooText { ref text } => {
if text == "pattern" {
} else {
}
}
}
}
// Possible?
fn match_text_fails(foo_text: &FooText) {
match foo_text {
&FooText { text: "pattern" } => (),
_ => (),
}
}
Its probably not "elegant" or any nicer.. but one option is to move the conditional into the match expression: 它可能不是“优雅”的或更好的..但是一种选择是将条件移到match表达式中:
match foo_text {
&FooText { ref text } if text == "pattern" => (),
_ => ()
}
Note that your desired pattern would actually work with a &str
. 请注意,您想要的模式实际上可以与
&str
。 You can't directly pattern match a String
because it's a more complex value that includes an unexposed internal buffer. 您不能直接对
String
模式匹配,因为它是一个更复杂的值,其中包括未暴露的内部缓冲区。
struct FooText<'a> {
text: &'a str,
_other: u32,
}
fn main() {
let foo = FooText { text: "foo", _other: 5 };
match foo {
FooText { text: "foo", .. } => println!("Match!"),
_ => println!("No match"),
}
}
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