小编Lon*_*olf的帖子

我有以下代码，我想将yreact组件的值传递给moveVertically关键帧。有可能这样做吗？

import React from 'react';
    import styled, {keyframes} from 'styled-components';


    const moveVertically = keyframes`
        0% {
            transform : translateY(0px) 
        }
        100% {
            transform : translateY(-1000px) //I need y here
        }
    `;

    //I can access y in here via props but can't send it above
    const BallAnimation = styled.g`
        animation : ${moveVertically} ${props => props.time}s linear
    `;


    export default function CannonBall(props) {

        const cannonBallStyle = {
            fill: '#777',
            stroke: '#444',
            strokeWidth: '2px',
        };

        return (
            <BallAnimation time …

我有一个函数需要递归地传递闭包参数

use std::cell::RefCell;
use std::rc::Rc;

pub struct TreeNode {
    val: i32,
    left: Option<Rc<RefCell<TreeNode>>>,
    right: Option<Rc<RefCell<TreeNode>>>,
}

pub fn pre_order<F>(root: Option<Rc<RefCell<TreeNode>>>, f: F)
where
    F: FnOnce(i32) -> (),
{
    helper(&root, f);

    fn helper<F>(root: &Option<Rc<RefCell<TreeNode>>>, f: F)
    where
        F: FnOnce(i32),
    {
        match root {
            Some(node) => {
                f(node.borrow().val);
                helper(&node.borrow().left, f);
                helper(&node.borrow().right, f);
            }
            None => return,
        }
    }
}

这不起作用：

use std::cell::RefCell;
use std::rc::Rc;

pub struct TreeNode {
    val: i32,
    left: Option<Rc<RefCell<TreeNode>>>,
    right: Option<Rc<RefCell<TreeNode>>>,
}

pub fn pre_order<F>(root: Option<Rc<RefCell<TreeNode>>>, f: F)
where …