angular - TS2531: Object is possibly 'null'

Question

I have the following function:-

uploadPhoto() {
    var nativeElement: HTMLInputElement = this.fileInput.nativeElement;

    this.photoService.upload(this.vehicleId, nativeElement.files[0])
        .subscribe(x => console.log(x));
}

however on the nativeElement.files[0], I am getting a typescript error, "Object is possibly 'null'". Anyone can help me solve this issue?

I tried to declare the nativeElement as a null value, however did not manage to succeed.

Thanks for your help and time.

question from:https://stackoverflow.com/questions/49431880/ts2531-object-is-possibly-null

Answer 1

files is defined to be FileList | null so it can be null.

You should either check for null (using an if) or use a "Non-null assertion operator" (!) if you are sure it is not null:

if(nativeElement.files != null) {
    this.photoService.upload(this.vehicleId, nativeElement.files[0])
        .subscribe(x => console.log(x));
}

//OR
this.photoService.upload(this.vehicleId, nativeElement.files![0])
    .subscribe(x => console.log(x));

Note:

The "Non-null assertion operator" will not perform any runtime checks, it just tells the compiler you have special information and you know nativeElement.files will not be null at runtime.

If nativeElement.files is null at runtime, it will generate an error. This is not the safe navigation operator of other languages.