Question

我是生锈的新手。我正在尝试实现一个全局静态数组（可以在多线程中访问它）并将一些结构实例插入其中。通过迭代数组，我可以调用这些实例的功能来执行某些操作。但是我遇到了一个问题，即不能插入带有生命周期注释的结构实例。示例代码和错误信息如下。您能提供一些建议吗？预先感谢！

#[macro_use]
extern crate lazy_static;

use std::sync::{Arc, Mutex};

struct Data {
    data: Vec<u8>,
}

trait CallbackFn {
    fn write_fn(&self, state: &[u8], data: &mut Data);
    fn read_fn(&self, data: &mut Data);
}

pub struct ArrayInst {
    idstr: &'static str,
    cb_fn: Box<CallbackFn + Send>,
}

impl ArrayInst {
    fn process_write(&self, i: &[u8], d: &mut Data) {
        self.cb_fn.write_fn(i, d);
    }

    fn process_read(&self, d: &mut Data) {
        self.cb_fn.read_fn(d);
    }
}

lazy_static! {
    static ref INST_ARRAY: Arc<Mutex<Vec<ArrayInst>>> = Arc::new(Mutex::new(vec![]));
}

pub fn inst_push(inst: ArrayInst) {
    INST_ARRAY.lock().unwrap().push(inst);
}

pub fn inst_pop() -> ArrayInst {
    INST_ARRAY
        .lock()
        .unwrap()
        .pop()
        .expect("Cannot find ArrayInst")
}

struct InstTest<'a> {
    name: &'static str,
    id: &'a u32,
}

impl<'a> InstTest<'a> {
    fn new(id: &'a u32) -> Self {
        InstTest {
            name: "InstTest",
            id: id,
        }
    }

    fn register_inst(self) {
        let inst = ArrayInst {
            idstr: "Test",
            cb_fn: Box::new(self),
        };
        inst_push(inst);
    }
}

impl<'a> CallbackFn for InstTest<'a> {
    fn write_fn(&self, val: &[u8], data: &mut Data) {
        let mut v: Vec<u8> = val.iter().cloned().collect();
        data.data.append(&mut v);
        println!("save val is {:?}", val);
    }

    fn read_fn(&self, data: &mut Data) {
        println!("load val is {:?}", data.data);
        println!("Current component name is {}", self.name);
    }
}

fn main() {
    let i: u32 = 10;
    let inst = InstTest::new(&i);
    let mut data = Data { data: Vec::new() };

    inst.register_inst();

    let inst = inst_pop();
    println!("idstr is {}", inst.idstr);

    let a = [1u8, 2, 3];
    let i: &[u8] = &a;
    inst.process_write(i, &mut data);
    inst.process_read(&mut data);
}

错误消息：

   Compiling playground v0.0.1 (/playground)
error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
  --> src/main.rs:62:29
   |
62 |             cb_fn: Box::new(self),
   |                             ^^^^
   |
note: first, the lifetime cannot outlive the lifetime 'a as defined on the impl at 51:6...
  --> src/main.rs:51:6
   |
51 | impl<'a> InstTest<'a> {
   |      ^^
   = note: ...so that the expression is assignable:
           expected InstTest<'_>
              found InstTest<'a>
   = note: but, the lifetime must be valid for the static lifetime...
   = note: ...so that the expression is assignable:
           expected std::boxed::Box<(dyn CallbackFn + std::marker::Send + 'static)>
              found std::boxed::Box<dyn CallbackFn + std::marker::Send>

error: aborting due to previous error

是否可以将带有生命周期注释的结构实例插入静态数组中？

0 个答案: