Question

我试图动态地从表单中收集输入数据，而不是键入每个单独的输入字段名称。使用标准React，这很容易，但是我要切换到React Hooks，现在我对如何实现相同目标有些困惑。

const gatherFormData = e => {
  if (e.target.value !== null) {
    _.assign(
      formData.payload,
      { [e.target.name]: e.target.value, action },
      { groupNumber },
    );
    setState({ 
      [e.target.name]: (e.target.value),
      formData
    });
  }
};

我尝试使用模板文字语法，但这没用。

set`${e.target.name}`(e.target.value);

Answer 1

您可以将useState与对象配合使用，以使其可以动态添加内容。示例：

const [targets, setTargets] = useState({});
// Set values like this
setTargets({...targets, [`${e.target.name}`]: e.target.value});

// Then get values:
const theValue = targets.yourTargetNameHere

设置值时，必须使用spread syntax（{...targets）来保持放置在对象中的其他值。

Answer 2

private void readFromServer() throws Throwable {
    String testSite = "https://sites.google.com/site/myName/test.txt";      
    HttpURLConnection urlConn = getFile(testSite);
    InputStream inStream = urlConn.getInputStream();
    doSomethingWith(inStream);
    inStream.close();
    urlConn.disconnect();
}

private static HttpURLConnection getFile(String testSite) throws Throwable {
    HttpURLConnection.setFollowRedirects(false);
    URL txtUrl = new URL(testSite);
    HttpURLConnection urlConn = (HttpURLConnection)txtUrl.openConnection();
    int timeout = 15000;
    urlConn.setConnectTimeout(timeout); //15 seconds
    urlConn.setReadTimeout(timeout);
    urlConn.setAllowUserInteraction(false);
    urlConn.setDoOutput(false);
    urlConn.setInstanceFollowRedirects(false);

    //Log.v(TAG, "Request URL ... " + txtUrl);
    urlConn = handleRedirects(urlConn, testSite);

    return urlConn;
}

private static HttpURLConnection handleRedirects(HttpURLConnection urlConn, String testSite) throws Throwable
{
    final int maxRedirect = 10;
    int numRedirect = 0;
    boolean isRedirect;
    String referer = testSite;

    do {
        isRedirect = mustRedirect(urlConn);

        if (isRedirect) {
            String newAddress = urlConn.getHeaderField("Location");
            String cookies = urlConn.getHeaderField("Set-Cookie");

            urlConn = (HttpURLConnection) new URL(newAddress).openConnection();
            urlConn.setRequestProperty("Cookie", cookies);
            urlConn.addRequestProperty("Referer", referer);

            referer = newAddress;
            numRedirect++;
        }
    } while (isRedirect && (numRedirect < maxRedirect));

    return urlConn;
}

private static boolean mustRedirect(HttpURLConnection urlConn) throws Throwable
{
    int status = urlConn.getResponseCode();
    if (status == HttpURLConnection.HTTP_OK) {
        return false;
    }
    return isMoved(status);
}

private static boolean isMoved(int status) { // normally, 3xx is redirect
    return status == HttpURLConnection.HTTP_MOVED_TEMP
            || status == HttpURLConnection.HTTP_MOVED_PERM
            || status == HttpURLConnection.HTTP_SEE_OTHER
            || status == -1; //returns -1 instead of 301. (no valid response code)
}

使用React钩子的动态表单字段

2 个答案: