错误TypeError：无法读取typescript中未定义的属性“filter”

Question

在此部分代码中显示此错误：Cannot read property 'filter' of undefined

  contrat: Contrat[];
  gpss: GPS[];
  homeboxp: HomeboxP[];
  sensors: Sensors[];
  homebox: Homebox[];

  getProductName(productid: string) {
    const [filteredProd] = this.contrat.filter(pt => pt.contrat_id === productid);
    const [filteredProdG] = this.gpss.filter(pt => pt.gps_id === productid);
    const [filteredProdhbp] = this.homeboxp.filter(pt => pt.homeboxpackage_id === productid);
    const [filteredProdh] = this.homebox.filter(pt => pt.homebox_id === productid);
    const [filteredProds] = this.sensors.filter(pt => pt.sensors_id === productid);

    if (typeof filteredProd !== 'undefined' && productid === filteredProd.contrat_id) {
      return filteredProd.contratdesc;
    } else if (typeof filteredProdG !== 'undefined' && productid === filteredProdG.gps_id) {
      return filteredProdG.gps_serial;
    } else if (typeof filteredProdhbp !== 'undefined' && productid === filteredProdhbp.homeboxpackage_id) {
      return filteredProdhbp.serial_number;
    } else if (typeof filteredProdh !== 'undefined' && productid === filteredProdh.homebox_id) {
      return filteredProdh.serial_number;
    } else if (typeof filteredProds !== 'undefined' && productid === filteredProds.sensors_id) {
      return filteredProds.sensor_serial;
    }
  }

你能说服我吗，这部分有什么问题？工作得很好，但显示此错误

提前致谢

Answer 1

在使用数组之前，必须先对其进行初始化：

  contrat: Contrat[] = [];
  gpss: GPS[] = [];
  homeboxp: HomeboxP[] = [];
  sensors: Sensors[] = [];
  homebox: Homebox[] =[];