Capacitor download and open file from api

Issue

I'm working on an Angular Ionic 7 App with capacitor 5. At one page of my app is a list of different files (pdf, txt,csv). The user can select a file and it should download to the device. I tryed to create a Object Url and open it with window.open(fileURL), but nothing happens, also no error. I tryed the library @capacitor/filesystem with downloadFile() Api. The result contins a blob but I'm not able to store it on the device. Does anybody know how to do this?

 Filesystem.downloadFile({ path: Directory.Data, url: url, directory: Directory.Data }).then((res) => {
    console.log('download finished');
  });

Solution

With the help of Raphaël Balet's Answer I played around and found a shorter solution. For the downloadFile() api use at least the file name to store the file inside the directory. As url i use an api path.

 // download the file to file system or open it in browser
  selectFile() {
    const url = this.createFileUrl('api/issues/attachement/' + this.messageId + '/' + this.attachment.id);
  
    if (Capacitor.isNativePlatform()) {
      Filesystem.downloadFile({
        path: this.attachment.attachmentName,
        url: url,
        directory: Directory.Documents,
      }).then((res: DownloadFileResult) => {
        this._openFileWithType(res.path, this.attachment.attachmentType);
      });
    } else {
      Browser.open({ url: url });
    }
  }

  //  Open the file
  private async _openFileWithType(filePath: string, fileType: string) {
    const fileOpenerOptions: FileOpenerOptions = {
      filePath: filePath,
      contentType: fileType,
    };

    await FileOpener.open(fileOpenerOptions)
      .then(() => {
        // 'File is opened'
      })
      .catch((error) => {
        console.error(error);
      });
  }

Answered By - keschra