Dart Built-in types

Dart Built-in Primitive Types Table

Category	Type Identifier	Declaration / Literal Example	Brief Description
Numbers	int, double	int a = 10; double b = 3.14;	Two numeric subtypes: integers and double-precision floating points, both inherit from the parent type num
Strings	String	var str = "foxdevelop.com";	Stores UTF-16 character sequences; supports string interpolation, multi-line text and raw strings
Booleans	bool	bool flag = true;	Only two valid values: true and false
Records	Record literal (v1, v2)	var record = (10, "test");	Fixed-length composite type holding multiple values; supports destructuring assignment
Functions	Function	void fn() {} Function func = ()=>1;	First-class objects that can be assigned to variables, passed as arguments and returned from functions
Lists (Arrays)	List	var list = [1,2,3];	Ordered collection allowing duplicate elements, equivalent to arrays in other languages
Sets	Set	var set = {1,2,3};	Unordered collection with unique non-duplicate elements
Maps (Key-Value Pairs)	Map	var map = {"name":"Tom"};	Key-value storage structure where all keys must be unique
Runes (Unicode Code Points)	Runes	Runes("\u{1f600}")	Low-level access to string Unicode code points; the official characters package is recommended as a replacement
Null	Null	Null n = null;	Holds only the null value; core top-level type under Dart’s null safety system

Every variable in Dart is fundamentally an object (an instance of a class). You can quickly create instances using literals, or initialize them by calling their corresponding constructors.

'hello' is a string literal, true is a boolean literal; Map() creates a Map via its constructor.

Special Auxiliary Language Types

These are not core primitive built-in types, but they are reserved Dart keywords.

These types serve special roles including type system management, asynchronous operations and static type checking:

Type	Purpose
Object	The parent class of all Dart types except Null
Enum	Base parent class for all enumerations
Future / Stream	Built exclusively for asynchronous programming workflows
Iterable	Used with for-in loops and synchronous generators
Never	Marks expressions that never complete normal execution (commonly used for functions that always throw exceptions)
dynamic	Disables static type checking; prefer Object / Object? instead
void	Signifies no return value, most commonly used as a function return type

1. Numbers

Parent supertype: num

The numeric system has two subclasses: int for integers and double for floating-point numbers, both extending num.

1.1 int (Integer)

Value ranges differ by platform (Dart also compiles to web, which uses JavaScript under the hood):

• Native platforms: -2^63 ~ 2^63 - 1
• Web (JS backend): -2^53 ~ 2^53 - 1

Integers contain no decimal points and support decimal and hexadecimal notation prefixed with 0x

Example

void main() {
    // Decimal integer
    var pageCount = 123;

    // Hexadecimal value
    var hex = 0xDEADBEEF;

    // Underscore number separators (Dart 3.6+ for readability)
    var million = 1_000_000;
    var mac = 0x00_14_22_01_23_45;

    print(pageCount);
    print(hex);
    print(million);
    print(mac);
}Code language: PHP (php)

Output

123
3735928559
1000000
86469845829

1.2 double (Double-Precision Float)

Values include decimal points or scientific notation syntax

void main() {
    var pi = 3.14; // Standard decimal float
    var raid = 1.61e5; // Scientific notation = 1.61 * 10^5
    var tiny = 0.000_000_000_02; // Underscore separators for decimals

    print(pi);
    print(raid);
    print(tiny);
}Code language: PHP (php)

3.14
161000.0
2e-11Code language: CSS (css)

1.3 Parent Type num

Variables declared as num can store both int and double values interchangeably:

void main() {
    num money = 5;
    money += 2.5; // Automatically converted to double, money = 7.5

    // Integers auto-convert to doubles when assigned
    double zoom = 1;

    print(money);
    print(zoom);
}Code language: PHP (php)

Output

7.5
1.0Code language: CSS (css)

1.4 Cross-Type Conversion

void main() {
    // String → int
    var one = int.parse('123');


    // String → double
    var pi = double.parse('3.14');

    // int / double → String
    String intStr = 99.toString();
    String pi2 = 3.14159.toStringAsFixed(2); // Round to 2 decimal places → "3.14"


    print(one);
    print(pi);
    print(pi2);
}Code language: JavaScript (javascript)

Output

123
3.14
3.14Code language: CSS (css)

1.5 int Exclusive Bitwise Operators

Only integer values support bit shifting, bitwise AND/OR/XOR and bitwise NOT. See this guide for details: Dart Bitwise and shift operators – FoxDevelop

void main() {
    print(3 << 1);  // Left shift: 0011 <<1 → 0110
    print(3 | 4);   // Bitwise OR
    print(3 & 4);   // Bitwise AND
    print(~3);       // Bitwise NOT
}Code language: PHP (php)

6
7
0
-4

1.6 Numeric Compile-Time Constants

Pure numeric literals and arithmetic operations between constants can be marked with const

A compile-time constant is a value fully calculated during compilation (before the program runs). Its value never changes at runtime and requires no live computation, declared with the const modifier.

const msPerSec = 1000;
const waitSec = 5;
const waitMs = waitSec * msPerSec; // Compile-time constant expressionCode language: JavaScript (javascript)

const: Compile-time constant — the compiler evaluates the expression’s fixed value before program launch and embeds it directly in the compiled binary; the value is read directly at runtime with no calculation overhead.

final: Runtime constant — assigned once when the program executes and cannot be overwritten after initial assignment.

1.7 Built-in Math Methods

Core helper methods come built into num; import dart:math for advanced mathematical operations

Common methods: abs(), ceil(), floor(), round()

num n = -3.6;
print(n.abs()); // 3.6
print(n.ceil()); // -3
print(n.floor()); // -4Code language: PHP (php)

2. String

Stores a UTF-16 encoded character sequence for representing text. Strings can be wrapped in either single or double quotation marks.

2.1 Declaration Syntax: Single vs Double Quotes

var s1 = 'Single quote string';
var s2 = "Double quote string";

// Escape special characters with backslash
var s3 = 'It\'s ok';
var s4 = "It's ok"; // Mixing quote types removes escape requirements
Code language: JavaScript (javascript)

Certain characters carry special parsing meaning inside strings (such as double quotes ", newlines and backslashes \). Writing them raw breaks string syntax and triggers compiler errors.

The escape character \ disables the special behavior of reserved characters and renders invisible control symbols.

Hidden input characters like carriage returns and tab keys require escape sequences to display correctly. For example \t inserts a tab character — run the sample code below to see how it works.

  print("name\tage\tcountry");
  print("Jack\t18\tUSA");
  print("Lucy\t20\tEgypt");Code language: PHP (php)

2.2 String Interpolation ${expression}

• Omit curly braces for simple variables: $variable
• Objects automatically invoke their .toString() method for text conversion

void main() {
    var word = "interpolation";
    var str1 = "Dart has $word";
    var str2 = "Uppercase: ${word.toUpperCase()}";
    print(str2); // Output: Uppercase: INTERPOLATION
}Code language: JavaScript (javascript)

2.3 String Concatenation

1. Adjacent string literals auto-concatenate, even across line breaks
2. Concatenate using the + operator

var s1 = "First line"
    "Second line";
var s2 = "a" + "b";
assert(s1 == "First lineSecond line");
assert(s2 == "ab");Code language: JavaScript (javascript)

2.4 Multi-line Strings: Triple Quotes ”’ / “””

void main() {
    var multi1 = '''
    Multi
    line
    text
    ''';

    var multi2 = """
    Triple double quote multi-line
    hello foxdevelop.com
    """;

    print(multi1);
    print(multi2);

}Code language: PHP (php)

        Multi
        line
        text

        Triple double quote multi-line
        hello foxdevelop.comCode language: CSS (css)

Single triple quotes allow unescaped double quotes inside, and triple double quotes support raw single quotes with no escape characters required:

2.5 Raw Strings r”” — Disables all escape sequence parsing

var raw = r"Newline escape \n will not be processed";
print(raw); // Prints literal \n as written
Code language: PHP (php)

2.6 Limitations for const Constant Strings

All content inside interpolations must be compile-time constants (numbers, booleans, const strings); regular variables and collections are not permitted

const num cNum = 10;
const bool cBool = true;
const String cStr = "const";
// Valid constant string interpolation
const valid = "$cNum $cBool $cStr";

var normalNum = 10;
// Invalid: interpolation references a non-constant variable 
// const invalid = "$normalNum";
Code language: JavaScript (javascript)

3. bool Boolean Type

Only two possible instances: true and false, both compile-time constants

Dart enforces strict static typing: implicit truthy/falsy checks are not allowed; explicit comparisons are mandatory

void main() {
    var emptyStr = "";
    print(emptyStr.isEmpty); // Check for empty string

    var zero = 0;
    print(zero == 0); // Explicit zero comparison

    var nil = null;
    print(nil == null); // Check null values

    var nan = 0 / 0;
    print(nan.isNaN); // Detect Not-a-Number values

}Code language: PHP (php)

4. Runes & characters — Working with Unicode Text

1. Runes: Legacy API to access raw Unicode code points inside strings
2. Recommended alternative: package:characters, which handles complete visual grapheme clusters (such as flag emojis)

Unicode Escape Syntax

• 4-digit hexadecimal codes: \uXXXX
• Larger multi-digit code points: \u{hex-value}

var heart = "\u2665"; // ♥
var laugh = "\u{1f606}"; // 😆
Code language: JavaScript (javascript)

package:characters Example

import 'package:characters/characters.dart';
void main() {
  var text = "Hi 🇩🇰";
  print(text.characters.last); // Outputs the full Denmark flag emoji
}
Code language: JavaScript (javascript)

5. Symbol

Used for reflection and code obfuscation workflows. Literal syntax is #identifier, and all Symbols are compile-time constants

Symbols remain unchanged after code minification/obfuscation, making them ideal for dynamically referencing identifiers by name

#userName
#getData
Code language: CSS (css)

6. Null Type

Holds exactly one value: null. Under Dart null safety, Null exists as an independent top-level type compatible with all nullable type declarations.

String? name = null;
Null n = null;
Code language: JavaScript (javascript)