Map does not have a null-aware-chainable "get" method

[srawlins]

Take the following example:

void fn(List<Map> listOfMaps) {
  var x = listOfMaps?.elementAt(0)["key"];
}

I am accessing the first element of listOfMaps, guarding against null, with listOfMaps?.elementAt. However, if listOfMaps is null, then so is listOfMaps?.anything, so an exception will be raised when ultimately [] is called on null.

The solution to this for property access is to chain null-aware all the way down, i.e. foo?.bar.baz.quux should be foo?.bar?.baz?.quux to be safe. But this cannot be done for operators like [].

In the case of a List, you can replace list[i] with list?.elementAt(i), but there is no equivalent method for Map. I propose V get(K key) or V get(Object key).

[ThinkDigitalSoftware]

I agree. I've been having to work around this too by explicitly checking if the map is null first.
I like the optional get method, like Java has, allowing for myMapOrList?.get() or a myMapOrList?[keyOrIndex], which looks funny, but technically would fall in line with putting a ? after the object in question.

[ThinkDigitalSoftware]

In fact, I'd like to propose a few changes that touch on this point.
Since we have null operators to execute or assign if n object is null, why not include operators to run or execute if an object isn’t? say, myInt !? myInt++ or myObject !?= newValue;
also, if Dart allows for the null aware operators to be used in conjunction with operators, it would solve this problem and also allow for

myInt?++ //  does this get in the way of the syntax for the proposed non-nullable types?

[jamesderlin]

Also see #28389.

BTW, I would be very much in favor of V get(K key) not only for null-aware-chainability but also to have a version of operator[] that type-checks the key.

[leafpetersen]

We are adding a null aware subscript operator as part of the upcoming NNBD release. See additional discussion here.