Dart is an open-source, general-purpose, object-oriented programming language with C-style syntax developed by Google in 2011. The purpose of Dart programming is to create a frontend user interfaces for the web and mobile apps. It can also be used to build server and desktop applications.
void main(){
// code goes here
}There are different ways to initialize a variable in Dart. The straight forward and recommended way is by using the keyword var.
var personName = 'John Doe';
var personAge = 25;Based on the value assigned into a variable, Dart will automatically infer data type to that variable. In the above example, Dart will automatically give the type of String to personName and int to personAge.
After initializing a variable with certain type of data using var keyword, it is not possible to assign a different type of data in the same variable later.
Suppose if we try to assign personName = 123 we get the following error message
“A value of type ‘int’ can’t be assigned to a variable of type
String"
unlike var keyword we can fit in any data type to variables using Object and dynamic
Object and dynamic keywords are often understood as inter-changable.
Example:
// Using object
void main(){
Object objvar = "John Doe";
print(objvar);
objvar = 124;
print(objvar);
}// Using dynamic
void main(){
dynamic dynvar = "John Doe";
print(dynvar);
dynvar = 124;
print(dynvar);
}Here both keywords will give same output:
John Doe
124
Note!!!
Eventhough they show the same output, they are usually not interchangeable.
In Dart, dynamic and Object are both types that can hold values of any type. However, they have some key differences:
| dynamic | Object |
|---|---|
dynamic is a type that tells the Dart compiler to skip type checking at compile time. This means that the type of a dynamic variable can be determined at runtime. |
Object is a class in Dart's core library. It is the root of the Dart class hierarchy and is a supertype of all Dart types, meaning every class and data types are extended from Object. When you use Object, you still have to adhere to Dart's static typing rules, which means you have to perform explicit type conversions when necessary. |
There are several built-in data types, including:
int: used to store integers
double: used to store floating-point numbers
String: used to store text
bool: used to store true or false value
List: used to store ordered collections of objects
Map: used to store unordered collections of key-value pairs