Wednesday, June 20, 2018

Dart: Variable

Welcome to the series post.
The is the first post about Dart

From today I am starting Dart language tutorial.
I already posted a brief introduction about dart and I also try to answer why you choose the dart programming. Check this Dart Introduction

In the previous post, I write about some important concept about dart. Before starting I recommend for taking a look.

Main method:
First, see the code:
void main(List<String> lists) {
}
In the code, you see that the parameter of the main method is a list of string. I think this is as usual of other programming languages. But most interesting part is that you can also create the main method without this parameter.
void main() {
}

So, That's so simple.
Now write a hello world program, to print something on the console, use print() function.
void main(List<String> lists) {
  print("Hello world");
}
Output:
Hello world

That's is the hello world program.
Now you can modify this program as yourself.

Variables:
Var:
To declare any variable you can use var keyword.
var v = 10;
you can put any type of data, like, Int, Double, String or anything
var string = "String";
var int = 10;
var double  = 30.0;
var boolean = false;

If you don't specify the value by default it considers as null
var value; //value is null

dynamic
You can use another keyword available name dynamic.
dynamic s = "s";
this dynamic type of variables can also hold any type of data, like var
dynamic string = "String";
dynamic int = 10;
dynamic double  = 30.0;
dynamic boolean = false;

You can also specify the data type of the data
String value;
int number;
double number2;
bool status;

Multiple variables:
You can also initialize multiple variables at the same time.
var a,b,c,d,e;
also, you can specify the value
var a1 = 10,b2 = 20,c2 = 30;

final and const:
If you need a variable that's value is not change after the declaration, use final keyword
final name = "Shudipto";
also the option for specific variables
final String type = "Student"; //explicitly

If you need runtime constant variables, then use const keyword
const value = 1000;
specific variable
const String data = "data:$value";

Lest see an example-
var foo = const [];
final bar = const [];
const baz = const [];
Here, [] create an empty list. and const[] creates an empty immutable list, it's denoted as (EIL)
In the above code,
foo => foo is currently an EIL.
bar => bar will always be an EIL.
baz => baz is a compile-time constant EIL.

It is possible to change the value of a non-final, non-const variable,
even if it used to have a const value.
foo = [];

It is not possible to change the value of a final or const variable.
// bar = []; // Unhandled exception.
// baz = []; // Unhandled exception.

that's it of the variable.

Comments:
single line comment: as usual like other languages. use '//'
//single line comment

multiline comment:
/*
* multi line comment
*/


That's the ending of today post.
Today in this article, I covered Hello world program and variable and Comments.

Thank you for reading.

Happy coding.

About Author:

I am Shudipto Trafder,
Since 2015, I write android code. I love to implement new ideas. I use java and also kotlin. Now I am learning Flutter. I love to learn new things and also love to share. And that is the main reason to run this blog.


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