Manually set value object's properties in typescript-CodePudding

I am trying to manually set a value object's properties if the data for it does not exist from the service call.

The data comes from a service call (it works, because I get data back). The object looks from the service call looks like this:

export class AllHouseData {
    dataList: HouseResponse[];
    numberOfHouses: number;
}

The value object for the HouseResponse object looks like this:

export class HouseResponse {
    id: number;
    name: string;
    settings: HouseSettings[];
}

The value object for the HouseSettings object looks like this:

export class HouseSettings {
    id: number;
    houseCode: string
    parking: any;
}

Here is the code where I am trying to assign the object's properties:

export class HouseComponent implements OnInit {
    houseData: AllHouseData;

    callHouseService(houseList) {
        this.houseService.getHouseData(houseList).subscribe((data) => {
            this.houseData = data;
            if (data === null) {
                this.houseData.dataList = [
                    {
                        id: 0,
                        name: "",
                        settings: [{ id: number, houseCode: "", parking: false }],
                    },
                ];
            }
        });
    }
}

Typescript gives me no errors when trying to set the data manually. However, in the console of the browser, I get the following error: ERROR TypeError: Cannot set properties of null (setting 'dataList').

My question is, what is the correct way to go about setting this object manually?

CodePudding user response：

Looks like your getHouseData call is returning null and you have no check for this.

If you need this.houseData to always have a value I would recommend a constructor with default values.

export class HouseSettings {
  constructor(public id = 0, houseCode = '', parking = false) {}
}
export class HouseResponse {
  constructor(public id = 0, name = '', public settings = [new HouseSettings()]) {}
}

export class AllHouseData {
  constructor(public dataList = [new HouseResponse()], public numberOfHouses = 0) {}
}

then in your subscription you could simply use:

data => this.houseData = data ?? new AllHouseData()