Dart null / false / empty checking: How to write this shorter?

Question

This is my code for true on everything but empty string, null and false:

if (routeinfo["no_route"] == "" || routeinfo["no_route"] == null || routeinfo["no_route"] == false) {     // do sth ... } 

This is my code for true on everything but empty string, null, false or zero:

if (routeinfo["no_route"] == "" || routeinfo["no_route"] == null || routeinfo["no_route"] == false || routeinfo["no_route"] == 0) {     // do sth... } 

How can I write this shorter in Dart? Or is it not possible?

Answer 1

If your requirement was simply empty or null (like mine when I saw this title in a search result), you can use Dart's safe navigation operator to make it a bit more terse:

if (routeinfo["no_route"]?.isEmpty ?? true) {   //  } 

Where

• isEmpty checks for an empty String, but if routeinfo is null you can't call isEmpty on null, so we check for null with
• ?. safe navigation operator which will only call isEmpty when the object is not null and produce null otherwise. So we just need to check for null with
• ?? null coalescing operator

If your map is a nullable type then you have to safely navigate that:

if (routeinfo?["no_route"]?.isEmpty ?? true) {   // } 

Answer 2

You could do

if (["", null, false, 0].contains(routeinfo["no_route"])) {   // do sth }