Dart

Intro to Dart Data Types

Hans Tan

• 3 min read
Intro to Dart Data Types

Data types are the building blocks of every programming language. In Dart, a data type is a variable that holds a value. It's very similar to the variables in math. Think about the x variable in math. x can be a representation of a certain value - a number. In Computer Science, that certain value can represent a lot more things than a number; the value can be a text, the value can be either true or false, or it can represent other values. Let's take a look at the syntax of declaring variables in dart:

(Data Type) (Variable Name) = Value;

    int          age        =  100;
     ^            ^             ^
     |            |             |
(Data Type) (Variable Name) = Value;

Examples:

bool isSmart = true;
String message = "Hello World";
double pi = 3.14;

Let's take a look at the most commonly used data types in Dart. Try them out in DartPad.

Boolean

A boolean is a data type that can hold either one of the following values - true or false. It's usually used in conditional statements. The boolean type is denoted by the shortcut bool.

Example usage:

void main() {
  bool isRaining = true;
  
  if (isRaining) {
    print("It's currently raining.");
  } else {
    print("It's not raining right now.");
  }
}

String

A string is a data type that represents a bunch of text. In dart, it holds a sequence of UTF-16 code units. You can use single or double quotes to create a string:

void main() {
  String message = "Hello World";
  print(message);
}

Integer

An integer is a data type that represents a whole number. In dart, the integer is 64-bit. The integer type is denoted by the shortcut int.

Example usage:

void main() {
  int x = 4;
  int y = 3;
  print(x + y);
}

Double

A double is a data type that can represent numbers with decimals.

Example usage:

void main() {
  double x = 3.85;
  double y = 2.18;
  print(x + y);
}

Lists

A list is a data type that can represent a list of variables. The list type is denoted by the shortcut List<T>, where T is a data type. If I want to represent a list of integers, the list type should be denoted as List<int>.

Example usage:

void main() {
  List<int> numbers = [1, 3, 5, 7, 9, 11];
  int total = 0;
  for (int number in numbers) {
    total+=number;
    // total+=number; is a shortcut for total = total + number;
  }
  print(total);
}

It is also possible to access the element of a list using list[index], where index is the (n-1)th element of the list. For example, if I want to access the 1st element of the list, I would do so using list[0], and if I want to access the 2nd element of the list, I would do so using list[1]. Note that index starts at 0 instead of 1.

Example usage:

void main() {
  List<int> numbers = [1, 3, 5];
  print(numbers[0]); // Output : 1
  print(numbers[1]); // Output : 3
  print(numbers[2]); // Output : 5
}

Map

A map is a data type that holds key-value pairs.

Maps allows you to quickly lookup a certain value by referencing its key. The syntax is as follows: map["key"]

For example:

void main() {
  Map<String, String> user = {
    "firstName": "Bill",
    "lastName": "Gates",
    "username": "BGates",
  };

  print(user["firstName"]); // Output: Bill
  print(user["lastName"]); // Output: Gates
  print(user["username"]); // Output: BGates
}

Sources: