Dart List Map Index

Dart is a programming language that offers flexible and easy-to-use tools for working with lists, maps, and indexes. In this article, we will explore how to work with these tools in Dart, specifically focusing on the List, Map, and index objects.

Lists

In Dart, a List is an ordered collection of items, where each item has an index position. To create a list in Dart, simply use the following syntax:

List<DataType> listName = [item1, item2, item3];

where DataType represents the type of data that the list will hold, and item1, item2, and item3 represent the values that will be stored in the list.

To access an item in a list, you can use its index position. For example, to access item1 in the previous list, you would use the following syntax:

listName[0]; // returns item1

You can also use the forEach method to iterate over all items in a list:

listName.forEach((item) => print(item));
// output: item1
//         item2
//         item3

Maps

In Dart, a Map is an unordered collection of key-value pairs, where each key must be unique. To create a map in Dart, use the following syntax:

Map<keyType, valueType> mapName = {
  key1: value1,
  key2: value2,
  key3: value3
};

where keyType and valueType represent the data types of the keys and values, respectively, and key1, key2, and key3 represent the keys of the map.

To access a value in a map, you can use its key:

mapName[key1]; // returns value1

You can also use the forEach method on the map's entries object to iterate over all key-value pairs:

mapName.entries.forEach((entry) => print('${entry.key}: ${entry.value}'));
// output: key1: value1
//         key2: value2
//         key3: value3

Index

In Dart, the index property is a built-in property that returns the index position of the current item in a forEach loop. For example, consider the following list:

List<String> names = ['Alice', 'Bob', 'Charlie'];

If we want to iterate over each item in the names list and print its index position, we can use the following code:

names.forEach((name) => print('${name} is at index ${names.indexOf(name)}'));
// output: Alice is at index 0
//         Bob is at index 1
//         Charlie is at index 2

Note that using indexOf to get the index position of an item in a list can be slow for large lists. In this case, consider using a for loop instead:

for (int i = 0; i < names.length; i++) {
  print('${names[i]} is at index ${i}');
}

Conclusion

In this article, we explored how to work with lists, maps, and indexes in Dart, including how to create and access them, how to iterate over them, and how to use the built-in index property. By mastering these tools, you will be well-equipped to handle a wide range of data structures in your Dart projects.