可以递归地定义React prop类型吗？

Question

假设我们正在定义一个将显示树的React类.

React.createClass({
    propTypes: {
        tree: treeType
    },
    render: function () {
        // ...
    }
});

这里的定义treeType显然不起作用,但希望说明我想表达的内容.

var treeType = React.PropTypes.shape({
    value: React.PropTypes.string,
    children: React.PropTypes.arrayOf(treeType)
})

有没有办法让类型懒惰地引用自己,这样可以工作？

Answer 1

React prop类型只是一个函数,所以它可以像这样懒惰地引用:

function lazyFunction(f) {
    return function () {
        return f.apply(this, arguments);
    };
}

var lazyTreeType = lazyFunction(function () { 
    return treeType;
});

var treeType = React.PropTypes.shape({
    value: React.PropTypes.string.isRequired,
    children: React.PropTypes.arrayOf(lazyTreeType)
})

完整工作示例的其余代码(也可作为jsfiddle提供):

function hasChildren(tree) {
    return !!(tree.children && tree.children.length);
}

var Tree = React.createClass({
    propTypes: {
        tree: treeType
    },
    render: function () {
        return this.renderForest([this.props.tree], '');
    },
    renderTree: function (tree, key) {
        return <li className="tree" key={key}>
            <div title={key}>{tree.value}</div>
            {hasChildren(tree) &&
                this.renderForest(tree.children, key)}
        </li>;
    },
    renderForest: function (trees, key) {
        return <ol>{trees.map(function (tree) {
            return this.renderTree(tree, key + ' | ' + tree.value);
        }.bind(this))}</ol>;
    }
});

var treeOfLife = { value: "Life", children: [
    {value: "Animal", children: [
        {value: "Dog"},
        {value: "Cat"}
    ]},
    {value: "Plant"}
]};

React.render(
    <Tree tree={treeOfLife}/>,
    document.getElementById('tree'));

结果截图:

Answer 2

这是另一种方法，由GitHub 上的jethrolarson 提供：

给定递归组件 Tree

import React from 'react';

const Tree = ({treeData}) => (
    <div>
        {treeData.nodeName}{' '}
        {treeData.children.map(subTree => (
            <Tree treeData={subTree} />
        ))}
    </div>
);

它采用如下所示的树数据结构

                Root
                /  \
           Child1   Child2
          /     \        \
     GChild1   GChild2   GChild3

（作为代码：

const treeData = {
    nodeName: "Root",
    children: [
        {
            nodeName: "Child1",
            children: [
                {nodeName: "GChild1"},
                {nodeName: "GChild2"},
            ]
        },
        {
            nodeName: "Child2",
            children: [
                {nodeName: "GChild3"},
            ]
        },
    ]
};

),

该propTypes对Tree可以被定义为：

import PropTypes from 'prop-types';

const treeDataShape = {
    nodeName: PropTypes.string.isRequired,
};
treeDataShape.children = PropTypes.arrayOf(PropTypes.shape(treeDataShape));

Tree.propTypes = {
    treeData: PropTypes.shape(treeDataShape),
};

注意所有引用如何引用treeDataShape同一个对象。children在创建对象之后进行定义可以递归地引用同一个对象。