web - FnMut 的问题

问题描述

我正在尝试使用 Rust 学习 WASM，并且正在使用该web_sys库。

我正在处理的页面有一个带有的输入id，player_name_button以及一个带有 player_name_button 的按钮。按照本教程Closures，当我尝试在按钮单击上放置行为时，出现编译器错误：

   |
84 |               let a = Closure::wrap(Box::new(move || {
   |  ___________________________________^
85 | |                 name_input_value = value(&mut Some(player_name_input));
86 | |                 if name_input_value == String::new() {
87 | |                     alert("Por favor informe o nome!");
...  |
93 | |                 }
94 | |             }) as Box<dyn FnMut()>);
   | |______________^ expected an `FnMut<()>` closure, found `[closure@src\lib.rs:84:44: 94:14 player_name_input:web_sys::features::gen_Element::Element, name_input_value:std::string::String, player_storage:player::player::PlayerSotorage]`

下面是代码：

let player_name_input = document
    .get_element_by_id("player_name_input")
    .expect("should have #num-clicks on the page");

let mut name_input_value = String::new();
//

let a = Closure::wrap(Box::new(move || {
    name_input_value = value(&mut Some(player_name_input));
    if name_input_value == String::new() {
        alert("Please informe the name!");
    } else {
        let mut p = Player {
            name: name_input_value,
        };
        player_storage.insert(p);
    }
}) as Box<dyn FnMut()>);
document
    .get_element_by_id("player_name_button")
    .expect("should have #player_name_button on the page")
    .dyn_ref::<HtmlElement>()
    .expect("#player_name_button be an `HtmlElement`")
    .set_onclick(Some(a.as_ref().unchecked_ref()));

// See comments in `setup_clock` above for why we use `a.forget()`.
a.forget();

这是 Cargo.toml

[lib]
crate-type = ["cdylib", "rlib"]

[build-dependencies]
askama = "0.7.2"

[dependencies]
wasm-bindgen = "0.2.60"
js-sys = "0.3.37"
askama = "0.7.2"
console_error_panic_hook = "0.1.5"

[dependencies.web-sys]
version = "0.3.5"
features = [
  'console',
  'CssStyleDeclaration',
  'Document',
  'DomStringMap',
  'DomTokenList',
  'Element',
  'Event',
  'EventTarget',
  'HtmlBodyElement',
  'HtmlElement',
  'HtmlInputElement',
  'KeyboardEvent',
  'Location',
  'Node',
  'NodeList',
  'Storage',
  'Window',
]

# The `console_error_panic_hook` crate provides better debugging of panics by
# logging them with `console.error`. This is great for development, but requires
# all the `std::fmt` and `std::panicking` infrastructure, so isn't great for
# code size when deploying.
console_error_panic_hook = { version = "0.1.1", optional = true }

# `wee_alloc` is a tiny allocator for wasm that is only ~1K in code size
# compared to the default allocator's ~10K. It is slower than the default
# allocator, however.
#
# Unfortunately, `wee_alloc` requires nightly Rust when targeting wasm for now.
wee_alloc = { version = "0.4.2", optional = true }

[dev-dependencies]
wasm-bindgen-test = "0.2"

[profile.release]
# Tell `rustc` to optimize for small code size.
opt-level = "s"

标签： webrustsys

这是由两个可能的原因之一引起的。我不知道是哪一个，但他们在这里：

player_name_inputorname_input_value变量在闭包之后使用。
该player_name_input变量包含对的引用document。

这两个问题都会导致闭包 not be 'static，即它将包含对存储在自身外部的值的引用。这是一个问题，因为Box<dyn FnOnce()>隐含地有一个Box<dyn FnOnce() + 'static>要求。在第一种情况下，这是对其中一个变量的引用，在第二种情况下，它将是对document.

请注意，您的比较String::new()可以替换为.is_empty().

web - FnMut 的问题

问题描述

解决方案

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