是否可以将对象方法作为参数传递给函数并将其绑定到对象? [英] Is it possible to pass an object method as argument to a function and bind it to the object?

问题描述

是否可以绑定到对象方法?例如，我有一个向量和许多函数，如果向量中存在某些项目，它们会执行某些操作.我会按如下方式实现它:

Is it possible to make a bind to object method? For example, I have a vector and a lot of functions which do something if some item exists in the vector. I would implement it as follows:

fn perform_if_exists(item: u8, vector: &Vec<u8>, func: fn(usize)) {
    let idx = vector.iter().position(|i| *i == item );
    match idx {
        Some(i) => func(i), 
        None    => {},
    }
}

fn main() {
    let v: Vec<u8> = vec![1, 2, 3];
    perform_if_exists(1, &v, Vec<_>::remove);
}

但它给出了很多错误.我认为它们是合理的，但这是因为我不明白如何将 vector 的方法作为函数的参数.

but it gives a lot of errors. I think they are reasonable but it's because I don't understand how to put vector's method as argument to a function.

推荐答案

有没有可能

当然是.您必须先修复多个级联错误:

Sure it is. You have to fix the multiple cascading errors first:

1. 无效语法:Vec<_>::remove 无效.
2. 不兼容的参数类型:Vec::remove 修改了 a Vec，所以你必须传入一个 Vec 不知何故.
3. 可变性:Vec::remove 修改一个Vec，所以你必须声明允许该函数这样做.
4. Vec::remove 返回移除的值，所以你必须允许函数返回一个值，即使它被丢弃.

1. Invalid syntax: Vec<_>::remove isn't valid.
2. Incompatible argument types: Vec::remove modifies a Vec, so you have to pass in a Vec somehow.
3. Mutability: Vec::remove modifies a Vec, so you have to declare that the function is allowed to do so.
4. Vec::remove returns the removed value, so you have to allow the function to return a value, even if it's thrown away.

fn perform_if_exists<F, R>(item: u8, vector: &mut Vec<u8>, func: F)
    where F: Fn(&mut Vec<u8>, usize) -> R
{
    let idx = vector.iter().position(|i| *i == item );
    if let Some(i) = idx {
        func(vector, i);
    }
}

fn main() {
    let mut v = vec![1, 2, 3];
    perform_if_exists(1, &mut v, Vec::remove);
    println!("{:?}", v);
}

我改用了泛型，因为这通常是您接受闭包的方式.函数指针很好，但限制更多.

I switched to a generic as that's generally how you will accept closures. A function pointer is fine but more restrictive.

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