Flutter null satety

다음과 같은 에러가 나타났다.

The property 'width' can't be unconditionally accessed because the receiver can be 'null'.
Try making the access conditional (using '?.') or adding a null check to the target 

해결 방법

• bang operator 사용

int? count = 1;

void main() {
  // will throw an error if count is null
  print(count! * 2);
}

• ?? operator 사용

int? count = 1;

void main() {
  // safe
  print((count ?? 1) * 2);
}

• if/else 구문 사용

int? count = 1;

void main() {
  if(count != null) {
    print(count! * 2);
  } else {
    print('count is null');
  }
}

https://stackoverflow.com/questions/66986024/the-operator-cant-be-unconditionally-invoked-because-the-receiver-can-be-n