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») => «value» --------------- («_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