Ts2532、Object 可能是“未定义”

Question

I'm trying to patch a task in a project that I'm creating with the mean stack. All the api's work, but when I try to patch an element, with the id param, there's an error which says:

"Object is possibly 'undefined'".

What I want to do is:

1. Get the element with a precise id
2. Use that id as query to patch that element

This is the code:

    export class TaskServicesService {
        
      constructor(private myHttp: HttpClient) { }
    
      async updateTask(payload: any) : Promise<any> {
        const task = await this.myHttp.get('http://localhost:3000/').toPromise();
        const elId: any = task.id;
        return await this.myHttp.patch('http://localhost:3000/list/', {title: payload}).toPromise();
      }
    
    }

Answer 1

The reason for this error is that the right value (rvalue) of the equation is probably undefined . One way to avoid this error is to check if an object is undefined before using it as a right value. I understand that in your application this error is caused by the task.id object. Hopefully we can fix this problem by:

if(task.id !== null && task.id !== undefined)
{
    const elId: task.id;
    return await this.myHttp.patch('http://localhost:3000/list/', {title: payload}).toPromise();
}
else
{
    /* Error Handling */
}

Answer 2

Try using optional chaining operator - ? :

const elId = task?.id;

If you are sure that task has value other than null or undefined , you can also use non-null assertion operator - ! :

const elId = task!.id;