Checking for null?

Question

In Dart we have simplified initialization of variables through the constructor:

e.g.

class Foo
{
    Bar _bar;

    Foo(this._bar);
}

At first glance this seems very convenient. But in my experience in 95% of the cases you would expect that what is sent in to a constructor should be non-null.

e.g. in C# I would write:

public class Foo
{
    private Bar bar;

    public Foo(Bar bar)
    {
         if (bar == null)
             throw new ArgumentNullException("bar");

         this.bar = bar;
    }
}

So my question is what the best-practice in Dart for null arguments is? Given that we have a language feature that basically discourages it?

Answer 1

In Dart's source code they throw ArgumentError.
Most time they don't check for null but the variable type.

int codeUnitAt(int index) {
  if (index is !int) throw new ArgumentError(index);
  // ...

Source: dart/sdk/lib/_internal/lib/js_string.dart#L17

factory JSArray.fixed(int length)  {
  if ((length is !int) || (length < 0)) {
    throw new ArgumentError("Length must be a non-negative integer: $length");
  }
  // ...

Source: dart/sdk/lib/_internal/lib/js_array.dart#L25