has been executed to the yellow part, res ["data"] .itemMaterialType = 3,
this.itemMaterialType= res [" data"] .itemMaterialType; this sentence has been executed, why this.itemMaterialType has always been the theoretical this.itemMaterialType=3 of undefined;.

the following is the encapsulation method,

  async searchData() {
    this.itemMaterialType = "4";
    await this.api.Dispatch.queryProcessDetailByProcessId({
      processId: this.processId
    })
      .then(res => {
        this.data = res["data"];
        this.isFeedMaterial = res["data"].isFeedMaterial.toString();
        this.itemMaterialType = res["data"].itemMaterialType;
      });
  }

    queryProcessDetailByProcessId: async (option) => await this.http.getByPromise("/api/ScheduleProcess/GetProcessDetail", option),

  async getByPromise(url: string, params: {}) {
    return await this.http.get(this.domain + url, { observe: "body", params: params })
      .toPromise();
  }