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1.2 Variables and Operators

Variables

var Property

When you want to initialize a variable, you can use var, this kind of initialization allows us set any type of data to this variable. Example:

var name = 'Alan',
var age = 31;

You cannot do this:

var name = 'Alan';
name = 21; // This is wrong

Once you create a variable with any type, this variable will keep that type of data in the whole program

Pre-defined variables

There is a way to define specificlly what type of data you want setting to each variable in the code.

int age = 31;
String name = "Alan"

Numeric

int n1 = 1;
double n2 = 1.5;

num n3 = 1;
num n4 = 1.5;

A double can be limited in decimals using toStringAsFixed() function.

double number1 = 22.998;
String numerWithTwoDecimals = (number1).toStringAsFixed(2);
// Result must be 22.99

String

String name = "Tux";
String lastname = "edo";

Concat:

String fullname = name + " " + lastname;

or

String fullname = "$name $lastname";

Booleans

bool light = false;
light = true;

Dynamic types

These are variables that could changes its value and type through the program excecution

dynamic example = "Hi, Im a example";
example = 23;

Fixed data types

They are fixed and cannot change its value through the program

final String example1 = "Alan"; // In compiling execution
const String example2 = "Alan2"; // In running execution

Both are unable to modify but one is using while the programm is running (const), by other way, final is a value defined in compilation time.

Convertions

We can convert from String to Integer or vice versa

String stringToNumber = "32";
int numberOk = int.parse(stringToNumber);

int numberToString = 32;
String stringOk = numberToString.toString();

String stringToDouble = "34.2";
double doubleOk = double.parse(stringToDouble);

Operators