Dart List: Handling Nullable Lists

Handling nullable lists in Dart involves understanding how Dart handles null values.

In Dart, variables can be declared as nullable by adding a ? after the type declaration, allowing them to hold either a value of the declared type or null.

When working with lists, this means that you can have a list that contains elements of a certain type or null values.

Here's a brief overview of how to handle nullable lists in Dart:

1. Declaring Nullable Lists: You can declare a nullable list by adding a ? after the type declaration:

    List<int>? nullableList;
   

2. Initializing Nullable Lists: Nullable lists can be initialized with null or an empty list:

    List<int>? nullableList = null;
    // or
    List<int>? nullableList = [];
   

3. Accessing Elements of Nullable Lists: Since the list can contain null elements, you need to check for null before accessing elements:

    if (nullableList != null) {
      // Access elements safely
      int? element = nullableList[0];
    }
   

4. Adding Elements to Nullable Lists: You can add elements to a nullable list as usual. However, remember to check for null before adding elements:

    if (nullableList != null) {
      nullableList.add(10);
    }
   

5. Iterating Over Nullable Lists: When iterating over nullable lists, you need to handle null elements:

    for (int? element in nullableList ?? []) {
      if (element != null) {
        // Process non-null elements
      }
    }
   

6. Null Safety Operators: Dart provides null safety operators like ?? and ?. to handle nullable values more concisely:

   • The ?? operator returns the value on its left if it's not null, otherwise, it returns the value on its right.

   • The ?. operator is used to access properties or methods of an object if the object is not null.

    int length = nullableList?.length ?? 0;

By using Dart's null safety features and handling nullable lists appropriately, you can write more robust and concise code that deals with nullable values effectively.