Glancing essential features of Dart, before stepping into Flutter

Kuala Lumpur
Wonyoung Choi
Lead Mobile Developer, OCBC Bank
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Glancing essential features
of Dart, before stepping
into Flutter

“Flutter is an open source framework by
Google for building beautiful, natively
compiled, multi-platform applications
from a single codebase.”

“But, This is not about Flutter.”

● Basic Syntax
● Object-Oriented Programming
● Functional Programming
● Asynchronous Programming

Variable / Constant
● int / double / String / bool
● Nullable / Non-nullable
● var - type inferring
dynamic - works like ‘Any’
● const - compile time
final - runtime
int attendees = 300;
double ticketPrice = 30.0;
String gdgChapter = "Kuala Lumpur”;
bool isHappy = true;

Variable / Constant
final - runtime
double? rotiTelur = null;
rotiTelur ??= 3.5;

Variable / Constant
final - runtime
var speakerName = "Toru";
speakerName = “Jecelyn";
dynamic month = "Dec";
month = 12;

Variable / Constant
final - runtime
final int year = 2022;
const String google = "Google";
final nextYear = 2023;
const myPhone = "Google Pixel 7 Pro";

Data Structures
● List: a basic collection like array
● Map: key-value pair
● Set: another basic collection, but not
allowing duplicated elements
List<String> btsMembers = [
"Jin",
"Suga",
"J-Hope",
"RM",
"Jimin",
"V",
"Jungkook"
];
btsMembers.add("Toru");
btsMembers.remove(“Toru");

Data Structures
Map<String, String> idols = {
"JYP": "TWICE",
“HYBE": "BTS",
"YG": "BLACKPINK"
};
idols["Starship"] = "IVE";
// What will happen?
print(idols["GDG"]);

Data Structures
final Set<String> blackPink = {
"Jisoo",
"Jennie",
"Rose",
"Lisa"
};
blackPink.add("Jisoo");
// What will happen?
print(blackPink);

Loop and condition
● if-else
● for loop
● while loop & do-while
● switch - with enum / given value

Method in Dart
● Return Type + Method name + Parameters
● named parameters with {}
● required keyword in parameters with {}
● optional parameters with []

Method in Dart
● Return Type + Method name + Parameters
● named parameters with {}
● required keyword in parameters with {}
● optional parameters with []
ReturnType methodName(ParameterType name) {
// Do whatever you want
}

Left Aligned Title
String namedParameter({
String first = "", String second = "", String third = ""
}) {
return "$first, $second, $third";
}
namedParameter(first: “Toru", second: “Android", third: "SG");

Left Aligned Title
String requiredParameter({
required String? first, required String? second
}) => "$first, $second";
To be nullable or with default value

String neitherRequiredAndNamed(
String first, String second
) => "$first, $second”;
neitherRequiredAndNamed("first", "second");

optionalParameter(String first, [String? second]) =>
"$first, $second”;
optionalParameter("first");
To be nullable or with default value

Class
● Constructor
● Private class
● Getter / Setter - additional properties
● Inheritance
● Abstract class / interface
class Employee {
String employeeName;
String employeeAddr;
// default constructor
Employee(
this.employeeName,
this.employeeAddr
);
// named constructor
Employee.initialize({
String? name, String? addr
}): employeeName = name ?? "",
employeeAddr = addr ?? "" {
// Do something
}
}

Class
● Constructor
● Private class
● Inheritance
class ImmutableEmployee {
final String employeeName;
final String employeeAddr;
// constant constructor,
// it means an immutable object will be created
const ImmutableEmployee(
this.employeeName,
this.employeeAddr
);
}
ImmutableEmployee ie =
const ImmutableEmployee(
"Toru", “Kuala Lumpur”
);

Class
class _GDGChapter {
final String chapterName;
final List<String> chapterMembers;
String country;
_GDGChapter(
this.chapterName,
this.chapterMembers,
this.country
);
}
● Constructor
● Private class
● Inheritance

Class
// getter
String get firstMember {
return chapterMembers[0];
}
// setter
set countryName(String countryName) => {
country = countryName;
print(country);
}
var gdgkl = _GDGChapter(...);
gdgkl.firstMember;
gdgkl.countryName = "Malaysia";
● Constructor
● Private class
● Inheritance

Class
class Idol {
String name;
int count;
Idol({
required this.name,
required this.count
});
void sayName() {
print('We are $name.');
}
void sayMembersCount() {
print('$name has $count members!');
}
}
● Constructor
● Private class
● Inheritance

Class
class BoyGroup extends Idol {
BoyGroup(
String name,
int count,
): super(
name: name,
count: count
);
sayBoyGroup() {
print('We are a boygroup!');
}
}
class GirlGroup extends Idol {
GirlGroup(
String name,
int count,
) : super(
name: name,
count: count
);
sayGirlGroup() {
print('We are a girlgroup!');
}
}
● Constructor
● Private class
● Inheritance

Class
abstract class IdolInterface {
String name;
IdolInterface(this.name);
void sayName();
}
class BoyGroup implements IdolInterface {
@override String name;
BoyGroup(this.name);
@override void sayName() {
print('We are $name.');
}
}
● Constructor
● Private class
● Inheritance
Abstract class works as an interface

Functional Programming in Dart
● Function as the first-order object
● Transforming from collections and map
● map()
● where()
● reduce()
Passed as a parameter,
Returned from a function,
Assigned into a variable.

void main() {
var f = greeting;
f('Hello KL');
greeting2("KL peeps,", (str)=>{print("Selamat Pagi, $str")});
}
greeting(String text) {
print('$text, we are GDG');
}
greeting2(String text, Function callback) {
callback(text);
}

● map()
● where()
● reduce()
final List<String> btsMembers = [
"Jin",
"Suga",
"J-Hope",
"RM",
"Jimin",
"V",
"Jungkook"
];
var btsSet = btsMembers.toSet();
var btsMap = btsMembers.asMap();

● map()
● where()
● reduce()
var btsSet = btsMembers.toSet();
var btsSet2 = Set.from(btsMembers);
var btsMap = btsMembers.asMap();

● map()
● where()
● reduce()
final List<String> blackPink = [
"Jisoo",
"Jennie",
"Rose",
"Lisa"
];
final newBP = blackPink.map((x) {
return 'BlackPink, $x';
}); // returns Iterable
print(newBP);

● map()
● where()
● reduce()
final List<String> blackPink = [
"Jisoo",
"Jennie",
"Rose",
"Lisa"
];
final newBP = blackPink.map((x) =>
‘BlackPink, $x’); // arrow function
print(newBP);

● map()
● where()
● reduce()
Map<String, String> idols = {
"JYP": "TWICE",
"HYBE": "BTS",
"YG": "BLACKPINK",
"Starship": "IVE"
};
final result = idols.map((k, v) =>
MapEntry(
'Enter corp $k', 'Idol $v’
)
);

● map()
● where()
● reduce()
List<Map<String, String>> gdg = [
{
'name': 'Toru',
'domain': 'Android'
},
{
'name': 'Hassan',
'domain': 'Android',
},
{
'name': 'Jecelyn',
'domain': 'Web',
},
{
'name': 'Vin',
'domain': 'Web',
}
];
final web = gdg.where((x) => x['domain'] == 'Web');
print(web.toList());

● map()
● where()
● reduce()
List<int> numbers = [1, 3, 5, 7, 9];
final result = numbers.reduce((prev, next) =>
prev + next
);
print(result); // result is 25
Must return the same type with parameters

● map()
● where()
● reduce()

Methods for FP are cascadable!

final list = ['Nasi Lemak', 'Roti Canai', 'CKT'];
var result =
list.map({ ... }).take(2).toList();

Asynchronous Programming
● Future - obtaining a value in the future.
● async, await - running code sequentially.
Future<String> futureStr = Future.value('GDG');
Future<int> futureInt = Future.value(100);

void main() {
print("Start");
Future.delayed(
Duration(seconds: 2), (){
print(["Toru", "Hassan", "Jecelyn"]);
});
print("End");
}
// Prints Start immediately
// Prints End immediately
// Prints the array 2 seconds later.

Future<List<String>> fetchSpeakers(String domain) async {
print("Start");
List<String> result = [];
await Future.delayed(
const Duration(seconds: 2), () {
print("Fetched");
if (domain == 'Android') {
result = ["Toru", "Hassan"];
} else {
result = ["Jecelyn", "Shang Yi"];
}
}
);
print("End");
return result;
}
void main() async {
final and = await fetchSpeakers('Android');
print("result: $and");
final other = await fetchSpeakers();
print("result: $other");
}
Use await, to call a method returning Future
Asynchronous!

How could we use Dart in more Dart way?

Thank you!
@TORU_0239
TORU0239
Linkedin: toruchoi

Glancing essential features of Dart, before stepping into Flutter

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