本文介绍了类型参数数量错误:应该为1,但发现为0的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试传递 std::io::BufReader
转换为功能:
I'm trying to pass a reference of std::io::BufReader
to a function:
use std::{fs::File, io::BufReader};
struct CompressedMap;
fn parse_cmp(buf: &mut BufReader) -> CompressedMap {
unimplemented!()
}
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut buf = BufReader::new(File::open("data/nyc.cmp")?);
let map = parse_cmp(&mut buf);
Ok(())
}
我收到此错误消息:
error[E0107]: wrong number of type arguments: expected 1, found 0
--> src/main.rs:5:24
|
5 | fn parse_cmp(buf: &mut BufReader) -> CompressedMap {
| ^^^^^^^^^ expected 1 type argument
我在这里想念什么?
推荐答案
看看 BufReader
的实现清楚地表明BufReader
具有必须指定的通用类型参数:
A look at the implementation of BufReader
makes it clear that BufReader
has a generic type parameter that must be specified:
impl<R: Read> BufReader<R> {
更改功能以说明type参数.您可以允许任何通用类型:
Change your function to account for the type parameter. You can allow any generic type:
use std::io::Read;
fn parse_cmp<R: Read>(buf: &mut BufReader<R>)
您还可以使用特定的具体类型:
You could also use a specific concrete type:
fn parse_cmp(buf: &mut BufReader<File>)
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