我怎么可以存储函数指针数组中？

问题描述

你如何坚持函数（或函数指针）到一个数组用于测试目的？

How do you stick functions (or function pointers) into an array for testing purposes?

fn foo() -> isize { 1 }
fn bar() -> isize { 2 }

fn main() {
    let functions = vec![foo, bar];
    println!("foo() = {}, bar() = {}", functions[0](), functions[1]());
}

这code。在<一个href=\"https://play.rust-lang.org/?gist=e89a4cbd1b7f2b73235c624a41167bc8&version=stable&backtrace=0\"相对=nofollow>锈游乐场

这是错误code我得到：

This is the error code I get:

error: mismatched types:
 expected `fn() -> isize {foo}`,
    found `fn() -> isize {bar}`
(expected fn item,
    found a different fn item) [E0308]

    let functions = vec![foo, bar];
                              ^~~

锈处理我的功能（值）不同类型，尽管有相同的签名，我觉得奇怪。

Rust is treating my functions (values) as different types despite having the same signatures, which I find surprising.

推荐答案

在某些时候日前，各功能被赋予它自己的，独特的类型...这我不记得的原因。结果是，你需要给编译器一个提示（注意函数类型）

At some point recently, each function was given its own, distinct type for... reasons that I don't recall. Upshot is that you need to give the compiler a hint (note the type on functions):

fn foo() -> isize {
    1
}
fn bar() -> isize {
    2
}
fn main() {
    let functions: Vec<fn() -> isize> = vec![foo, bar];
    println!("foo() = {}, bar() = {}", functions[0](), functions[1]());
}

您也可以做到这一点像这样：

You can also do this like so:

let functions = vec![foo as fn() -> isize, bar];

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