Angular2 Cannot read property 'push' of undefined

Question

Currently, I can make a call to a service and fill a table with records; the records have a selected property, which is toggled by checkboxes for each row.

Underneath that table is a button; when I hit the button, I want to loop through the table and create a new array with entries that have selected property == true.

I can't seem to initialize the selecterecords array properly.

Record.ts

export class Record {
    id: string;
    firstname: string;
    lastname: string;
    salary: string;
    selected : boolean;
}

table-component.ts

export class TableComponent implements OnInit {
    records: Record[];
    selectedrecords: Record[];

    constructor(
        private router: Router,
        private recordService: RecordService) {}

    getRecords(): void {
        this.recordService.getRecords().then(records => this.records = records);
    }

    ngOnInit(): void {
        this.getRecords();
    }

    createselectedRecords() {
        for (let rec of this.records) {
            if (rec.selected) {
                this.selectedrecords.push(rec);
            }
            console.log(this.selectedrecords);
        }
    }
}

record-service.ts

@Injectable()
export class RecordService {
    getRecords(): Promise<Record[]> {
        return Promise.resolve(RECORDS);
    }

    getRecord(id: string): Promise<Record> {
        return this.getRecords()
            .then(records => records.find(record => record.id === id));
    }
}

martin · Accepted Answer · 2017-07-08 12:20:14Z

4

By selectedrecords: Record[] you just set this property's type so TypeScript can warn you if you do anything wrong.

To actually initialize the property you can use an empty array:

selectedrecords: Record[] = [];

edited Jul 8, 2017 at 12:20

answered Nov 1, 2016 at 13:29

martin

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Comments

Sefa · Accepted Answer · 2016-11-01 13:28:40Z

0

You need to initialize before using your variable.

constructor(
 private router: Router,
 private recordService: RecordService) { 
 this.selectedrecords = new Array<Record>(); // <-- added 
}

answered Nov 1, 2016 at 13:28

Sefa

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