Dart & Flutter

Question 1

embed variable in string in D

Answer 1

‘«string» $«variable» «string»’

Question 2

statement in D

Answer 2

«statement»;

» always with semicolon

Question 3

entry point of D app

Answer 3

void main() {
  ...
}

» main function

Question 4

embed expression in string in D

Answer 4

‘«string» ${«expression»} «string»’

Question 5

multiline string in D

Answer 5

’’‘«multi line
string»’’’

””“«multi line
string»”””

Question 6

raw string in D

Answer 6

r’«raw string»’

» no special character treatment

Question 7

types in D

Answer 7

» void
» null
» dynamic
» bool
» int
» double
» String
» List (like Array in JS)
» Set (like unordered Array)
» Map (like Object in JS)

Question 8

comment in D

Answer 8

// «single line comment»

/* «multi line
comment» */

/// «single line documentation comment»

/** «multi line
documentation comment» **/

Question 9

declare variable in D

Answer 9

var «name»;
» reassignable

final «name»;
» runtime constant
» mutable
» not reassignable

const «name»;
» compile time constant
» not mutable
» not reassignable
» freezes data structures like Map and List

Question 10

declare class with fields in D
(f.ex. person)

Answer 10

class Person {
  String firstName, lastName, fullName;
  int age = 0;
}

Question 11

shuffle order of list in D

Answer 11

«list».shuffle();

Question 12

filter elements of list in D

Answer 12

«list».where((«element») => «check»);

Question 13

add element to list in D

Answer 13

«list».add(«element»);

Question 14

get part of list in D

Answer 14

«list».sublist(«start», «_end before»);

» returns a list object
» returns rest of original list if «_end before» is omitted

Question 15

remove specific elements from list in D

Answer 15

«list».removeWhere((«element») => «check»);

Question 16

import third party package in D

Answer 16

import ‘package:«package name»/«file name».dart’;

Question 17

import standard library in D

Answer 17

import ‘dart:«package name»’;

Question 18

import local file in D

Answer 18

import ‘«path»’;

Question 19

parse JSON in D

Answer 19

import ‘dart:convert’;

var «parsed json» = json.decode(«raw json»);

Question 20

access map values in D

Answer 20

«map»[«key»]

Question 21

import specific element of package in D

Answer 21

import «package» show «element»;

Question 22

create custom stateless widget in F

Answer 22

import ‘package:flutter/material.dart’;

class «name» extends StatelessWidget {
…
}

Question 23

create custom stateful widget in F

Answer 23

import ‘package:flutter/material.dart’;

class «name» extends StatefulWidget {
…
}

Question 24

show image from an URL in F

Answer 24

Image.network(«url»)

Question 25

set padding/margin widget in F

Answer 25

EdgeInsets
.only(_left: «val», _top: «val», _right: «val», _bottom: «val»)
.symmetric(_vertical: «val», _horizontal: «val»)
.fromLTRB(«val», «val», «val», «val»)
.all(«val»)
//.fromWindowPadding(«padding», «devicePixelRatio value»)

» val: double

Question 26

set border widget in F

Answer 26

Border(_top: «bs», _right: «bs», _bottom: «bs», _left: «bs»)
Border.symmetric(_vertical: «bs», _horizontal: «bs»)
Border.fromBorderSide(«bs»)
Border.all(_color: «color», _width: «width», _style: BorderStyle.«style»)

» bs: BorderSide
» style: solid or none

Question 27

set color widget by color code in F

Answer 27

Color(0̸xAARRGGBB)
Color.fromARGB(«alpha», «red», «green», «blue»)
Color.fromRGBO(«red», «green», «blue», «opacity»)

» 0̸x value must be 8 digits
» opacity: double

Question 28

use mixin in D

Answer 28

import ‘«path to mixin»’;

class «name» extends «class» with «mixin» {
…
}

» mixin: another _abstract class

Question 29

declare abstract class in D
(like interface in TS)

Answer 29

abstract class «name» {
  «_field»...
  «_constructor»...
  «_method»...
  «_abstract method»(«_type» «_prop»);
}

» cannot be instantiated
» abstract methods have to be implemented on »extends«

Question 30

implement class as an interface in D

Answer 30

class «name» implements «class» {
…
}

» inherits types only

Question 31

set default value for case that variable will be null in D

Answer 31

«variable to check» ?? «default value»

Question 32

arrow function in D

Answer 32

(«_type» «param», «_type2» «_param2») => {
…
return «value»;
}

» params always in brackets

Question 33

set border on container widget in F

Answer 33

Container(
  decoration: BoxDecoration(
    border: «Border»
  ),
),

Question 34

set border side widget in F

Answer 34

BorderSide(_color: «color», _width: «width», _style: BorderStyle.«style»))

» style: solid or none

Question 35

set border style widget in F

Answer 35

BorderStyle.«style»

» style: solid or none

Question 36

set color widget by material enum in F

Answer 36

Colors.«color»_[«intensity»]
Colors.«color»Accent[«intensity»]

» color: transparent, red, blue, grey etc.
» intensity: 100-900, default is 500
» accent intensity: 100, 400, 700, default is 200

Question 37

set color widget to black or white in F

Answer 37

Colors.«black|white»«_opacity»

» black opacity: 12, 26, 38, 45, 54, 87
» white opacity: 10, 12, 24, 30, 38, 54, 60, 70

Question 38

declare class with constructor in D
(f.ex. person)

Answer 38

class Person {
  String firstName, lastName, fullName;

Person(this.firstName, this.lastName) {
fullName = ‘$firstName $lastName’;
}
}

Question 39

declare class with named constructor in D
(f.ex. person)

Answer 39

class Person {
  String firstName, lastName, fullName;

  Person.dummy() {
    firstName = 'Bruce';
    lastName = 'Wayne';
    fullName = '$firstName $lastName';
  }
}

Question 40

declare class with method in D
(f.ex. person)

Answer 40

class Person {
  String name;

Person(this.name);

greet(String greeting) {
print(‘$greeting, $name’);
}
}

Question 41

declare class with getter and setter in D
(f.ex. person)

Answer 41

class Person {
  int birthYear;

  int get age => DateTime.now().year - birthYear;
  set age(int value) => birthYear = DateTime.now() - value; 
}

Question 42

inherit from other class in D

Answer 42

class «name» extends «class» {
…
}

» inherits types and implementations
» abstract methods have to be implemented now