Question

我试图基于用户ID getList（）获取显示名称getUserinfo（）我尝试过

使用变量捕获数据并将其馈送到getList（）。
使用状态变量设置状态并将数据传递给getList（）。但是状态似乎是异步的，所以失败了

问题：为什么我的getUserinfo（）无法为getList（）返回一个要使用的值？

 private getUserinfo(userid: number) {
    var result;
    let url;
    url = `/_api/web/GetUserById(${userid})`;
    const opt: ISPHttpClientOptions = {
      headers: { "Content-Type": "application/json;odata=verbose" }
    };

    this.props.spHttpClient
      .get(
        this.props.context.pageContext.web.absoluteUrl + url,
        SPHttpClient.configurations.v1,
        opt
      )
      .then((response: SPHttpClientResponse) => {
        response.json().then((json: any) => {
          if (json.Title) {
            let name = json.Title;
            let email = json.Email;
            let issiteadmin = json.IsSiteAdmin;

            //debugger;
            return name;  // this has value but it returns nothing in another function I called
          }
        });
      });
  }

private getList() {
    this.state.data.length = 0;
    const qurl =
      "/_api/web/lists/getbytitle('list')/items?$select=*&$orderby=Modified desc";

    const opt: ISPHttpClientOptions = {
      headers: { "Content-Type": "application/json;odata=verbose" }
    };

    this.props.spHttpClient
      .get(
        this.props.context.pageContext.web.absoluteUrl + qurl,
        SPHttpClient.configurations.v1,
        opt
      )
      .then((response: SPHttpClientResponse) => {
        response.json().then((json: any) => {
          for (let i = 0; i < json.value.length; i++) {

            let authorid = json.value[i].AuthorId;
            let editorid = json.value[i].Editorid;
            let Authorname = this.getUserinfo(authorid);
            let Editorname = this.getUserinfo(editorid);

            debugger;

            this.setState({
              data: [
                ...this.state.data,
                {

                  Authorname,
                  Editorname
                }
              ]
            });
          }
        });
      });
  }

Answer 1

由于您尚未从getUserInfo返回任何信息，因此您刚刚调用this.props.spHttpClient.get()而未返回其值，例如：

private getUserinfo(userid: number) {
  ...
  return this.props.spHttpClient.get( ... )
    .then((response: SPHttpClientResponse) => {
      return response.json().then((json: any) => {
        if (json.Title) {
          let name = json.Title;
          let email = json.Email;
          let issiteadmin = json.IsSiteAdmin;
          return name;  // this has value but it returns nothing in another function I called
        }
      });
  });
}

这样，当您致电this.getUserinfo(authorid)时，您将获得一个承诺，您可以按以下方式使用其值：

 this.getUserinfo(authorid).then( name => {
    // use its name
 });

Answer 2

这是您使用async / await编写它的方式，从而提高了可读性

for (Mat mat : mats) {
        Mat newMat = mat.clone();
        opencv_imgproc.Canny(mat, newMat, 50.0, 100.0);
        opencv_imgproc.blur(newMat, newMat, new Size(2, 2));
        opencv_core.MatVector contours = new opencv_core.MatVector();
        opencv_core.Mat hierarchy = new opencv_core.Mat();
        //Mat hierarchy = new Mat(new double[]{255, 255, 255, 0});
        opencv_imgproc.findContours(newMat, contours, hierarchy, opencv_imgproc.CV_RETR_TREE, opencv_imgproc.CHAIN_APPROX_NONE, new opencv_core.Point(0, 0));

        List<opencv_core.Rect> rectangles = new ArrayList<>();
        for (Mat matContour : contours.get()) {
           //clueless how to find internal contours here 
        }

您可以使用与getList相同的样式

React函数什么都不返回

2 个答案: