flutterdartdart-null-safetyflutter-image-picker

Flutter, dart: what's the difference between these snippets of code?


Code snippet A is working, but not snippet B. I check variable "image"s data type with print(), both A and B's image (variable) has a datatype (XFile), not a Null. But B is still not working....

final XFile? image = await _picker.pickImage(source: ImageSource.gallery);

print(image);

// Code snippet A
if (image == null) return null;
return File(image.path);

// Code snippet B
return File(image!.path);

Solution

  • The meaning of your code snippet A is:

    If the image variable is null it will return null otherwise it will return the image variable.

    The meaning of your code snippet B is:

    It returns the image variable, although the image variable may be null.

    If you use code snippet B, you use ! and change the variable from a nullable type to a non-nullable type, and the variable is actually empty (has no value) and you can't use .path so it returns an error.