Dart

What is Dart?

• Dart is a programming language developed by Google.
• Dart is a compiled, statically typed, general-purpose programming language.
• Dart is a multi-paradigm, object-oriented, open-source, platform-independent, and compiled language.
• Core of Flutter Framework.

Dart Syntax

• Whitespace and Line Breaks : Dart ignores spaces, tabs, and newlines.
• Case Sensitivity : Dart is case-sensitive. That means Dart differentiates between uppercase and lowercase letters. For example "Hello" and "hello" are not the same.
• Comments : Dart supports single-line and multi-line comments. Single-line comments start with "//" and end with a newline. Multi-line comments start with "/" and end with "/".
• Statements end with a semicolon : Each line of instruction is called a statement. Every statement must end with a semicolon (;).

Dart Data Types

• Numbers : Dart supports two types of numbers : integers int and doubles double.
• Strings : Dart supports strings String with single '' or double "" quotes.
• Lists : Dart supports lists List with square brackets ([]).
• Maps : Dart supports maps Map with curly brackets ({}).
• Booleans : Dart supports booleans with true and false.
• Null : Dart supports null.

Dart Variables

• A variable can be declared in Dart using the var keyword. For example, var x = 5;
• Dart supports type-checking by prefixing a variable with its type. For example, int x = 5; and double x = 5.0;
• Dart supports dynamic type. Variables declared without a static type are implicitly dynamic type. Variables declared using dynamic keyword in place of the var keyword. For example, dynamic x = 5; and dynamic x = "Hello";.
• The final and const keywords can be used to declare a variable as immutable. That means Dart prevents modification of the variable. For example, final x = 5; and const x = 5;

Dart Operators

• An expression is a special kind of statement that evaluates to a value. For example, 5 + 3; is an expression ending with a semicolon.

• Every expression is composed of operators and operands.

  • operands are representations of data.
  • operators are defines how the operands will be processed to produce a result.

  Operators:

  • Arithmetic Operators : Dart supports the following arithmetic operators : +, -, *, /, %, ~/, ++, --.

  • Comparison Operators : Dart supports the following comparison operators : ==, !=, >, <, >=, <=.

  • Logical Operators : Dart supports the following logical operators : &&, ||, !.

  • Assignment Operators : Dart supports the following assignment operators : =, +=, -=, *=, /=, %=, ~/=, <<=, >>=, &=, |=, ^=, ??=.

  • Conditional Operators : Dart supports the following conditional operators : ??, ??=.

  • Ternary Operator : Dart supports the ternary operator.

    condition ? expression1 : expression2;

Dart Control Flow

• Control Statements are used to control the flow of the program. There are three types of control statements in Dart :

  • Conditional Statements
  • Loop Statements
  • Jump Statements

  Conditional Statements:

  Dart supports if, else if, else and switch statements.

  • if statement
  • else if statement
  • else statement
  • switch statement

  Loop Statements:

  A loop is a block of code that can be executed repeatedly. Dart supports for, while, and do while loops.

  • for loop

    for (initialization; condition; increment/decrement) {
        //   block of code
    }

  • while loop

    initialization
    while (condition) {
        //   block of code
        increment/decrement
    }

  • do while loop

    initialization
    do {
        //   block of code
        increment/decrement
    } while (condition);

  Jump Statements:

  Dart supports break and continue statements.

  • break is used to exit a loop.
  • continue is used to skip an iteration in a loop.

Dart Lists

• A very commonly used collection in programming is array. Dart represents array as List. For example, List<int> list = [1, 2, 3];
• Operations on List :
  • Add - add() addAll()
  • Insert - insert() insertAll()
  • Remove - remove() removeAt() removeLast() removeRange() removeWhere()
  • Update - replaceRange() or manually list[index] = value
  • Sort - sort()
  • Length - length
  • Clear - clear()

Dart Maps

• The Map is a collection of key-value pairs. Keys and values can be of any type. A Map is a dynamic collection. Maps can be declared in two ways :

  • Using Map Literals

    var map = {
        "key1": "value1",
        "key2": "value2",
        "key3": "value3",
    }

  • Using the Map constructor

    var map = new Map();
    map["key1"] = "value1";
    map["key2"] = "value2";
    map["key3"] = "value3";

  • Operations on Map : addAll() containsKey() containsValue() forEach() remove() removeWhere() updateAll() clear() length isEmpty isNotEmpty

List vs Map

List	Map
Collection of Data	Collection of Data
List use index number	Map use keys
Dynamically increase and decrease	Dynamically increase and decrease
List is like an array	Map is like an object or associative array
1 element hold 1 data	1 element hold 2 data (key, value)

Dart Sets

• A set is a collection of unique elements. It is a dynamic collection.

• Sets can be declared in two ways :

  • Using Set Literals

    var set = {
        "value1",
        "value2",
        "value3",
    }

  • Using the Set constructor

    var set = new Set();
    set.add("value1");
    set.add("value2");
    set.add("value3");

  • Operations on Set : add() addAll() contains() remove() clear() length isEmpty isNotEmpty

Dart HashMap

• A HashMap is a hash table based implementation of Map. When you iterate through a HashMap's keys or values, you can't get the keys or values in any particular order.
• Syntax : HashMap<K, V> hashMap = HashMap(); where the K and V are the key and value types respectively.
• HashMap is same as Map except that HashMap doesn't allow duplicate keys and the order of elements is not specified.
• HashMap supports all the operations of Map

Dart HashSet

• A HashSet is a hash table based implementation of Set. When you iterate through a HashSet's elements, you can't get the elements in any particular order.
• Syntax : HashSet<K> hashSet = HashSet(); where the K is the key type.
• HashSet is same as Set.
• HashSet supports all the operations of Set.

Dart Functions

• Functions are a block of code that performs a specific task.

• Functions can be 4 types :

  • No Arguments and No Return Type

    void myFunction() {
        print("Hello World");
    }

  • No Arguments and With Return Type

    int myFunction() {
        return 1;
    }

  • With Arguments and No Return Type

    void myFunction(int a, int b) {
        print(a + b);
    }

  • With Arguments and With Return Type

    int myFunction(int a, int b) {
        return a + b;
    }

Object Oriented Programming (OOP) in Dart

• Dart is an object-oriented language. It supports object-oriented programming features like classes, interfaces, inheritance, polymorphism, and encapsulation.

• A class is a blueprint for creating objects. It defines the properties and behaviors that an object of that class will have.

• An object is an instance of a class. It contains the state and behavior of the class.

  Dart Classes and Objects

  • A class can defined by using class keyword.

  • A class can have variables, functions, and objects.

    class Person {
        String name;
        int age;
        void printInfo() {
            print("Name: $name, Age: $age");
        }
    }
    
    var person = new Person(); // Create an object of the `Person` class
    
    person.name = "John"; // Set the name of the person
    person.age = 30; // Set the age of the person
    
    person.printInfo(); // Print the name and age of the person

  • The this keyword refers to the current instance of the class. If the parameter name and the name of the class's property are the same, hence to avoid confusion, it is recommended to use the this keyword in Dart.

  Class in External File

  • A class can be defined in another file and imported in the main file.

    class Person {
        String name;
        int age;
        void printInfo() {
            print("Name: $name, Age: $age");
        }
    }

  • The Person class is defined in another file and imported in the main file.

    import 'person.dart';
    
    void main() {
        Person person = new Person();
        person.name = "John";
        person.age = 30;
        person.printInfo();
    }

  Inheritance

  • A class can inherit the properties and methods of another class.

  • Inheritance is a mechanism in which one class acquires the properties and methods of another class.

  • The extends keyword is used to inherit the properties and methods from another class.

  • The super keyword is used to access the properties and methods of the parent class.

  • The super keyword is used to call the parent class's constructor.

    // Parent class
    class Person {
        String name;
        int age;
        void printInfo() {
            print("Name: $name, Age: $age");
        }
    }
    
    // Child class
    class Employee extends Person {
    String department;
        // Constructor
        Employee(String name, int age, String department) {
            this.name = name;
            this.age = age;
            this.department = department;
        }
        // Override the `printInfo()` method
        @override
        void printInfo() {
            super.printInfo();
            print("Department: $department");
        }
    }
    
    // Main class
    void main() {
        Employee employee = new Employee("John", 30, "IT");
        employee.printInfo();
    }