Introduction - learn Dart

Dart by Google?

Dart 2 is statically typed.

With its combination of static and runtime checks, Dart has a sound type system, which guarantees that an expression of one type cannot produce a value of another type.

Even with type-safe Dart, you can annotate any variable with dynamic if you need the flexibility of a dynamic language. The dynamic type itself is static, but can contain any type at runtime. Of course, that removes many of the benefits of a type-safe language for that variable.

Every Dart app has a main() function. To display’s text, you can use the top-level print() function:

void main() {
print(‘Hello, World!’);
print(“hello world”);
}

output

** remember: single quote [‘ ’] or double quotes[“ ”] work same for print statements. When we use print() function, it generates a new-line every time.

Newline character(\n) – this character helps to generate new line in console or output screen.

void main(){
print(‘hey!!\n i am shimanta das’);
print(“hello”);
}

output

Tab character(\t) – generate tab between two characters.

void main(){
print(‘windows\tlinux’);
}

output

User input

User input means user can input via keyboard.

To take input from a user in Dart, you need to import the ‘dart:io’ library. The input is taken through the console using the .readLineSync() function. About ‘stdin’ Class: This class allows the user to read data from standard input in both synchronous and asynchronous ways.

Remember: you can’t take directly take Integer/double input instead of String input in Dart. For that after taking String variable input you need to typecast into integer/double and do whatever operations you want to do. This process also known as ‘typecasting’. You will learn about this later in the articles.

Note: The .runtimeType property is used to find out the runtime type of the object. The keyword var in Dart language lets a variable store any type of data. The .runtimeType property helps to find what kind of data is stored in the variable using var keyword.

Let’s work on taking String input…

Code 1:

import ‘dart:io’;

void main(){
String? str;
print(‘Enter Your String: ‘);
str = stdin.readLineSync();
print(‘your string: ‘);
print(str);
print(str.runtimeType);
}

output

Let’s work on taking integer input…

Code 2:

import ‘dart:io’;

void main(){
String? str;
// late -> values initialized later
late int a;

print(‘enter value: ‘);
str = stdin.readLineSync();

// converts string->integer explicitly(typecasting)
if (str!=null) {
a=int.parse(str);
}
print(‘a value ‘);
print(‘$a’);
print(‘variable A runtime-type: ‘);
print(a.runtimeType);
}

output

Let’s work on taking double input…

Code 3:

import ‘dart:io’;

void main(){
String? str;
late double val;

print(‘Enter Value: ‘);
str=stdin.readLineSync();

// implicit converts String->double
if (str!=null) {
val = double.parse(str);
}

print(‘double value is ‘);
print(val);
print(val.runtimeType);
}

output

Comments

Comments are those statements which are ignored by the interpreter in dart.

There are 2 types of comments –

Single-line
Multi-line

Single-line & multiline Comment

Let’s see the single-line & multi-line comment uses

void main(){
// single line comment

/*
multi line comment
line 1
line 2
line 3
*/
}

Comparison between Dart, Python, Java, C/C++

topic	Dart	C/C++	Python	Java
Learn	Easy	Moderate	easy	moderate
OOPS	All have but not so much control	All have & all controls	All have but not so much control	All have & all controls
Variables type	Static(default) & dynamic	Static	Dynamic	static
Modern application	Cross platforms application development with modern U.I	Cross platforms application development	Cross platforms application development	Cross platforms application development

Tools for dart development/coding…

You can use your own tool…

Windows – vs code, dart sdk

Linux – vs code, nano editor, dart sdk

Mac – vs code, dart sdk

Remember: if you want to online code compiler –

Dart-pad[recommended]: https://dartpad.dev/?

Jdoodle: https://www.jdoodle.com/execute-dart-online/

download notes

download code.zip