Dart programming language basics

-dart.md

Example programs with outputs for learning the fundamentals of the Dart programming language

1-datatypes.dart

//dart language is made up of c+python+javascript

void main(List<String> args) {
  print("hello world"); // output: hello world
  // datatypes available are int,double(use double for float),String, dynamic(allows to assign any datatype) ,var(like var in javascript)

  int x = 34;
  double y = 23.55;
  print(x); // output: 34
  print(x + y); // output: 57.55

  String name = "sourabh";
  print(name); // output: sourabh
  print("My name is " + name); // output: My name is sourabh
  print("My name is $name"); //formatted string // output: My name is sourabh

  //string functions
  print("Length of $name is " + name.length.toString()); // output: Length of sourabh is 7
  //or
  print("Length of $name is ${name.length}"); // output: Length of sourabh is 7

  dynamic num = 23;
  print(num); // output: 23
  num = "number";
  print(num); // output: number

  var a = 12;
  var b = "sourabh";

  print(a); // output: 12
  print(b); // output: sourabh
}

/* Output after execution:
hello world
34
57.55
sourabh
My name is sourabh
My name is sourabh
Length of sourabh is 7
Length of sourabh is 7
23
number
12
sourabh 
*/

2-arrays and loops.dart

void main(List<String> args) {
  //array or list
  var data = [23, 45, 657, 798, 2123, 108];
  print(data[0]); // output: 23
  print(data); // output: [23, 45, 657, 798, 2123, 108]

  //Loops
  //for loop
  for (int i = 0; i < 10; i++) {
    print(i);
  }
  print("\n");
  /*output: 0
            1
            2
            3
            4
            5
            6
            7
            8
            9 */

  for (int i = 0; i < data.length; i++) {
    print(data[i]);
  }
  print("\n");
  /* output:23
            45
            657
            798
            2123
            108 */

  for (var x in data) {
    print("Num is $x");
  }
  print("\n");
/* output:Num is 23
          Num is 45
          Num is 657
          Num is 798
          Num is 2123
          Num is 108 */

  //for each loop (from javascript)
  data.forEach((element) {
    print(element);
  });
/* output:23
          45
          657
          798
          2123
          108 */

  //while loop is same as in C lang
}

/* Output after execution:
23
[23, 45, 657, 798, 2123, 108]
0
1
2
3
4
5
6
7
8
9


23
45
657
798
2123
108


Num is 23
Num is 45
Num is 657
Num is 798
Num is 2123
Num is 108


23
45
657
798
2123
108
 */

3-functions and conditionals.dart

dynamic getArea(length) {
  return length * 4;
}

//dont use ; inside arrow fn
var getPerimeter = (length) => {
      //here length parameter is mandatory
      print(length), //output: 12
      print(length + 4), //output: 16
      print(length + 12), //output: 24
    };

var getOptionalArea = ([length]) => {
      //here length inside [] is optional. if argument is not mentional, it will be null
      //if,else if,else is same like in C lang
      if (length == null)
        {
          print("Please provide length"), //output: Please provide length
        }
      else
        {
          print(length), //output: 89
        }
    };

void main(List<String> args) {
  print("main fn"); //output: main fn
  var area = getArea(23);
  print(area); //output: 92

  getPerimeter(12);

  getOptionalArea();
  getOptionalArea(89);
}

/* Output after execution:
main fn
92
12
16
24
Please provide length
89 
*/

4-classes.dart

class Students {
  var name = "sourabh";
  var age = 20;

  Students() {
    print("Hello!"); //output: Hello!
    name = "neha";
    age = 12;
  }

  void displayName() {
    print("My name is ${this.name}"); //output: My name is neha
  }
}

void main(List<String> args) {
  var student = Students();
  print(student); //output: Instance of 'Students'
  print(student.name); //output: neha
  print(student.age); //output: 12

  student.displayName();
}


/* Output after execution:
Hello!
Instance of 'Students'
neha
12
My name is neha
*/