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在rust中迭代数组时出错

rust

zwl1619 · 技术社区 · 3 年前

我正在读取一个json文件,然后迭代一个数组,出现了一个错误:

D:\workspace\rust-projects\hello-rust (master)
Î» cargo run
   Compiling hello-rust v0.1.0 (D:\workspace\rust-projects\hello-rust)
error[E0599]: no method named `iter` found for enum `Value` in the current scope
  --> src\main.rs:69:46
   |
69 |             for item in note["sectionNotes"].iter() {
   |                                              ^^^^ method not found in `Value`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `hello-rust` due to previous error

代码如下:

test.json

{
    "sound": {
        "soundNotes": [
            {
                "sectionNotes": [],
                "lengthInSteps": 16
            },
            {
                "sectionNotes": [
                    [
                        11256.236,
                        2,
                        0
                    ]
                ],
                "lengthInSteps": 17
            },
            {
                "sectionNotes": [
                    [
                        13122.965,
                        3,
                        1
                    ],
                    [
                        13500,
                        0,
                        2
                    ]
                ],
                "lengthInSteps": 18
            }
        ]
    }
}

货物.toml

[dependencies]
delay_timer = "0.10.1"
serde_json = "1.0"
anyhow = "1.0.51"
smol = "1.2.5"

main.rs

use delay_timer::prelude::*;
use anyhow::Result;
use smol::Timer;
use std::time::Duration;
use std::fs::File;
use std::io::BufReader;
use serde_json::{Result as SResult, Value};

fn main() {

}


fn get_section_notes() -> SResult<Value> {
    let file = File::open("test.json").expect("file should open read only");
    let reader = BufReader::new(file);
    let mut v: Value = serde_json::from_reader(reader)?;
    Ok(v["sound"]["soundNotes"].take())
 }


fn build_task_async_print() -> Result<Task, TaskError> {
    let mut task_builder = TaskBuilder::default();

    let song_notes=get_section_notes();
    
    let body = create_async_fn_body!({
    
        for note in song_notes.iter() {
            for item in note["sectionNotes"].iter() {
            Timer::after(Duration::from_millis(item[0].round())).await;
                 println!("{}", item);;
             }
        }

    });

    // Build the task and assign 1 to it
    task_builder
        .set_task_id(1)
        .spawn(body)
}

请帮忙,谢谢!

更新1:
修改为之后 for item in note["sectionNotes"].as_array().unwrap() ,是这样的:

D:\workspace\rust-projects\hello-rust (master)
Î» cargo run
   Compiling hello-rust v0.1.0 (D:\workspace\rust-projects\hello-rust)
error[E0599]: no method named `round` found for enum `Value` in the current scope
  --> src\main.rs:70:60
   |
70 |                 Timer::after(Duration::from_millis(item[0].round())).await;
   |                                                            ^^^^^ method not found in `Value`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `hello-rust` due to previous error

更新2:

for note in song_notes.iter() {
            for item in note["sectionNotes"].as_array().unwrap() {
                let mut time=item[0].as_u64().unwrap();
                Timer::after(Duration::from_millis(time)).await;
                println!("{}", time);
             }
        }

错误

Î» cargo run
   Compiling hello-rust v0.1.0 (D:\workspace\rust-projects\hello-rust)
error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnOnce`
  --> src\main.rs:66:16
   |
66 |       let body = create_async_fn_body!({
   |  ________________^
67 | |
68 | |         for note in song_notes.iter() {
   | |                     ---------- closure is `FnOnce` because it moves the variable `song_notes` out of its environment
69 | |             for item in note["sectionNotes"].as_array().unwrap() {
...  |
75 | |
76 | |     });
   | |______^ this closure implements `FnOnce`, not `Fn`
...
81 |           .spawn(body)
   |            ----- the requirement to implement `Fn` derives from here
   |
   = note: this error originates in the macro `create_async_fn_body` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0525`.
error: could not compile `hello-rust` due to previous error

0 回复 | 直到 3 年前

AlexNe 3 年前

修复了上述错误。

use anyhow::Result;
use delay_timer::prelude::*;
use serde_json::{Result as SResult, Value};
use smol::Timer;
use std::fs::File;
use std::io::BufReader;
use std::time::Duration;

fn main() {}

fn get_section_notes() -> SResult<Value> {
    let file = File::open("test.json").expect("file should open read only");
    let reader = BufReader::new(file);
    let mut v: Value = serde_json::from_reader(reader)?;
    Ok(v["sound"]["soundNotes"].take())
}

fn build_task_async_print() -> Result<Task, TaskError> {
    let mut task_builder = TaskBuilder::default();

    
    let body = create_async_fn_body!({
        let song_notes = get_section_notes();  //put it here
        for note in song_notes.iter() {
            for item in note["sectionNotes"].as_array().iter() {
                // Error fixed
                Timer::after(Duration::from_millis(item[0].as_f64().unwrap().round() as u64)).await;
                println!("{:?}", item);
            }
        }
    });

    // Build the task and assign 1 to it
    task_builder.set_task_id(1).spawn(body)
}