SharePoint Rest API Post Request fail

Question

I try to fetch items from list in SharePoint 2019 using Rest API but the request fail with the following response Message:

"could not be resolved by the model. When a model is available, each type name must resolve to a valid type"

{"odata.error":{"code":"-1, Microsoft.SharePoint.Client.InvalidClientQueryException","message":{"lang":"en-US","value":"A type named 'SP.Data.Metadata\":\"http://orgaplums/teamsite/_api/$metadata#SP.ApiData.Lists/@Element&$select=Title\",\"odata.type\":\"SP.List\",\"odata.id\":\"http://orgaplums/teamsite/_api/Web/Lists(guid'fc03bd4c-7908-401e-9acf-2329470867f3')\",\"odata.etag\":\"\\\"3\\\"\",\"odata.editLink\":\"Web/Lists(guid'fc03bd4c-7908-401e-9acf-2329470867f3')\",\"Title\":\"MySurvey\"ListItem' could not be resolved by the model. When a model is available, each type name must resolve to a valid type."}}}

Here is my code used to fetch from API:

    public  async postVote(surveyListId: string, question: string, choice: string): Promise<boolean> {

    let listName = await this.getListName(surveyListId)
      alert("List Name : " + listName)
      var restUrl: string = this.context.pageContext.web.absoluteUrl;
      restUrl += "/_api/Web/Lists(guid'";
      restUrl += surveyListId;
      restUrl += "')/items";
      let contenttype = await this.getItemTypeForListName(listName)
      console.log("List Contenttype : " +contenttype)
      var item = {
          "__metadata": { "type": "SP.Data.MysurveyListItem" },
          "Title": "newItemTitle"
      };
      item[question] = choice;

      var options: ISPHttpClientOptions = {
        headers: {
          "odata-version": "3.0",
          "Accept": "application/json"
        },
        body: JSON.stringify(item),
        webUrl: this.context.pageContext.web.absoluteUrl
      };
      return this.context.spHttpClient.post(restUrl, SPHttpClient.configurations.v1, options).then((response: SPHttpClientResponse) => {
        return response.json().then((responseFormated: any) => {
          return true;
        });
      }) as Promise<boolean>;

  }

  private getListName(listId: string): Promise<string> {
    var restUrl: string = this.context.pageContext.web.absoluteUrl;
    restUrl += "/_api/Web/Lists(guid'";
    restUrl += listId;
    restUrl += "')?$select=Title";
    var options: ISPHttpClientOptions = {
      headers: {
        "odata-version": "3.0",
        "Accept": "application/json"
      }
    };
    return this.context.spHttpClient.get(restUrl, SPHttpClient.configurations.v1, options).then((response: SPHttpClientResponse) => {
        return response.text().then((responseFormated: string) => {
            var iTitle = responseFormated.indexOf("<d:Title>");
            var newStr = responseFormated.slice(iTitle + 9, responseFormated.length);
            newStr = newStr.slice(0, newStr.indexOf("</d:Title>"));
            return newStr;
        });
    });
  }

  // private getItemTypeForListName(name: string): string {
  //   return "SP.Data." + name.charAt(0).toUpperCase() + name.split(" ").join("").slice(1) + "ListItem";
  // }
  private getItemTypeForListName(listId: string) :Promise<string>  { //string {
    var restUrl: string = this.context.pageContext.web.absoluteUrl;
    restUrl += "/_api/Web/Lists(guid'";
    restUrl += listId;
    restUrl += "')?$select=ListItemEntityTypeFullName";
    var options: ISPHttpClientOptions = {
    headers: {
    "odata-version": "3.0",
    "Accept": "application/json"
    }
    };
    return this.context.spHttpClient.get(restUrl, SPHttpClient.configurations.v1, options).then((response: SPHttpClientResponse) => {
    return response.json().then((responseFormated: any) => {
    return responseFormated.ListItemEntityTypeFullName;
    });
    });

Answer 1

I think you are using wrong ListItemEntityTypeFullName in payload.

If you are getting correct ListItemEntityTypeFullName value from getItemTypeForListName() function, try using payload like:

var item = {"__metadata": { "type": contenttype }, "Title": "newItemTitle"};

Check my answer here to understand more about getting correct ListItemEntityTypeFullName: Pass file name having space to update operation using REST API