我得到一个Promise 当我执行console.log( mypost )

是的，因为apiFetch() 确实返回了Promise 对象，以及apiFetch() 不会将从服务器收到的响应分配给mypost 常量，以及then() 回调也不会分配给mypost 变量

如何获取post对象？

As suggested by React, 您需要添加mypost 作为组件中的本地状态，然后发出XHR/AJAX请求（使用apiFetch(), 本地人window.fetch(), Axios或其他）中的componentDidMount() 类组件的方法，或使用useEffect hook 在功能组件中。

示例使用apiFetch() 具有useEffect:

import { useState, useEffect } from \'@wordpress/element\';
import apiFetch from \'@wordpress/api-fetch\';

function MyComponent( { post_id } ) {
    const [ error, setError ]       = useState( null );
    const [ mypost, setPost ]       = useState( null );
    const [ isLoaded, setIsLoaded ] = useState( false );

    useEffect( () => {
        apiFetch( { path: `custombase/v1/post/${ post_id }` } ).then(
            ( result ) => {
                setIsLoaded( true );
                setPost( result );
            },
            ( error ) => {
                setIsLoaded( true );
                setError( error );
            }
        );
    }, [ post_id ] );

    if ( error ) {
        return <p>ERROR: { error.message }</p>;
    } else if ( ! isLoaded ) {
        return <p>Loading post { post_id }..</p>;
    } else if ( mypost && mypost.id ) {
        return <h3>Post <i>{ mypost.title || \'#\' + mypost.id }</i> loaded!</h3>;
    }
    return <p>No such post</p>;
}
// Sample usage: <MyComponent post_id="1239" />

替代解决方案：将自定义端点的实体添加到块编辑器中的实体列表中addEntities():

import { dispatch } from \'@wordpress/data\';

dispatch( \'core\' ).addEntities( [{
    baseURL: \'/custombase/v1/post\',
    // The \'post\' is not a post type - it\'s the "post" as in /post above. Also, "kind"
    // and "name" are not documented, so let\'s assume they form the above baseURL..
    kind: \'custombase/v1\',
    name: \'post\',
    label: \'Post or whatever\',
}] );

// You can, for example, call the above (i.e. add the entity) before you register your
// block type.

getEntityRecord() 要从终结点获取post数据，请执行以下操作：

const mypost = select( \'core\' ).getEntityRecord( \'custombase/v1\', \'post\', 1239 );
// Note that getEntityRecord() caches the results.

getEntityRecord() 要正常工作，端点回调必须使用小写id 而不是ID:

// In the get_post_rest() function:

$data = array(
    \'id\'    => $post->ID, // use id and *not* ID
    \'title\' => $post->post_title,
);

useSelect, 上述组件(MyComponent) 现在看起来是这样的：

import { useSelect } from \'@wordpress/data\';

function MyComponent( { post_id } ) {
    const { mypost, isLoading } = useSelect( ( select ) => {
        const args = [ \'custombase/v1\', \'post\', post_id ];

        return {
            mypost: select( \'core\' ).getEntityRecord( ...args ),
            isLoading: select( \'core/data\' ).isResolving( \'core\', \'getEntityRecord\', args )
        };
    }, [ post_id ] );

    if ( isLoading ) {
        return <p>Loading post { post_id }..</p>;
    } else if ( mypost && mypost.id ) {
        return <h3>Post <i>{ mypost.title || \'#\' + mypost.id }</i> loaded!</h3>;
    }
    return <p>No such post</p>;
}