Programming Kotlin Applications Building Mobile and Server Side Applications with Kotlin 1st Edition by Brett Mclaughlin 1119696186 9781119696186

1 Objects All the Way Down

KOTLIN: A NEW PROGRAMMING LANGUAGE

WHAT IS KOTLIN?

KOTLIN IS OBJECT-ORIENTED

INTERLUDE: SET UP YOUR KOTLIN ENVIRONMENT

CREATING USEFUL OBJECTS

INITIALIZE AN OBJECT AND CHANGE A VARIABLE

2 It’s Hard to Break Kotlin

UPGRADE YOUR KOTLIN CLASS GAME

KOTLIN HAS A LARGE NUMBER OF TYPES

OVERRIDING PROPERTY ACCESSORS AND MUTATORS

CLASSES CAN HAVE CUSTOM BEHAVIOR

TYPE SAFETY CHANGES EVERYTHING

WRITING CODE IS RARELY LINEAR

3 Kotlin Is Extremely Classy

OBJECTS, CLASSES, AND KOTLIN

ALL CLASSES NEED AN EQUALS(X) METHOD

EVERY OBJECT INSTANCE NEEDS A UNIQUE HASHCODE()

SEARCHING (AND OTHER THINGS) DEPEND ON USEFUL AND FAST EQUALS(X) AND HASHCODE()

BASIC CLASS METHODS ARE REALLY IMPORTANT

4 Inheritance Matters

GOOD CLASSES ARE NOT ALWAYS COMPLEX CLASSES

CLASSES CAN DEFINE DEFAULT VALUES FOR PROPERTIES

SECONDARY CONSTRUCTORS PROVIDE ADDITIONAL CONSTRUCTION OPTIONS

HANDLE DEPENDENT VALUES WITH CUSTOM MUTATORS

NEED SPECIFICS? CONSIDER A SUBCLASS

YOUR SUBCLASS SHOULD BE DIFFERENT THAN YOUR SUPERCLASS

5 Lists and Sets and Maps, Oh My!

LISTS ARE JUST A COLLECTION OF THINGS

LISTS (AND COLLECTIONS) CAN BE TYPED

LISTS ARE ORDERED AND CAN REPEAT

SETS: UNORDERED BUT UNIQUE

MAPS: WHEN A SINGLE VALUE ISN’T ENOUGH

FILTER A COLLECTION BY … ANYTHING

COLLECTIONS: FOR PRIMITIVE AND CUSTOM TYPES

6 The Future (in Kotlin) Is Generic

GENERICS ALLOW DEFERRING OF A TYPE

GENERICS TRY TO INFER A TYPE WHEN POSSIBLE

COVARIANCE: A STUDY IN TYPES AND ASSIGNMENT

CONTRAVARIANCE: BUILDING CONSUMERS FROM GENERIC TYPES

UNSAFEVARIANCE: LEARNING THE RULES, THEN BREAKING THEM

TYPEPROJECTION LETS YOU DEAL WITH BASE CLASSES

7 Flying through Control Structures

CONTROL STRUCTURES ARE THE BREAD AND BUTTER OF PROGRAMMING

IF AND ELSE: THE GREAT DECISION POINT

WHEN IS KOTLIN’S VERSION OF SWITCH

FOR IS FOR LOOPING

USE WHILE TO EXECUTE UNTIL A CONDITION IS FALSE

DO … WHILE ALWAYS RUNS ONCE

GET OUT OF A LOOP IMMEDIATELY WITH BREAK

GO TO THE NEXT ITERATION IMMEDIATELY WITH CONTINUE

RETURN RETURNS

8 Data Classes

CLASSES IN THE REAL WORLD ARE VARIED BUT WELL EXPLORED

A DATA CLASS TAKES THE WORK OUT OF A CLASS FOCUSED ON DATA

DESTRUCTURING DATA THROUGH DECLARATIONS

YOU CAN “COPY” AN OBJECT OR MAKE A COPY OF AN OBJECT

DATA CLASSES REQUIRE SEVERAL THINGS FROM YOU

DATA CLASSES ADD SPECIAL BEHAVIOR TO GENERATED CODE

DATA CLASSES ARE BEST LEFT ALONE

9 Enums and Sealed, More Specialty Classes

STRINGS ARE TERRIBLE AS STATIC TYPE REPRESENTATIONS

COMPANION OBJECTS ARE SINGLE INSTANCE

ENUMS DEFINE CONSTANTS AND PROVIDE TYPE SAFETY

SEALED CLASSES ARE TYPE-SAFE CLASS HIERARCHIES

10 Functions and Functions and Functions

REVISITING THE SYNTAX OF A FUNCTION

FUNCTIONS FOLLOW FLEXIBLE RULES

FUNCTIONS IN KOTLIN HAVE SCOPE

FUNCTION LITERALS: LAMBDAS AND ANONYMOUS FUNCTIONS

LOTS OF FUNCTIONS, LOTS OF ROOM FOR PROBLEMS

11 Speaking Idiomatic Kotlin

SCOPE FUNCTIONS PROVIDE CONTEXT TO CODE

USE LET TO PROVIDE IMMEDIATE ACCESS TO AN INSTANCE

WITH IS A SCOPE FUNCTION FOR PROCESSING AN INSTANCE

RUN IS A CODE RUNNER AND SCOPE FUNCTION

APPLY HAS A CONTEXT OBJECT BUT NO RETURN VALUE

ALSO GIVES YOU AN INSTANCE … BUT OPERATES ON THE INSTANCE FIRST

SCOPE FUNCTIONS SUMMARY

12 Inheritance, One More Time, with Feeling

ABSTRACT CLASSES REQUIRE A LATER IMPLEMENTATION

INTERFACES DEFINE BEHAVIOR BUT HAVE NO BODY

DELEGATION OFFERS ANOTHER OPTION FOR EXTENDING BEHAVIOR

INHERITANCE REQUIRES FORETHOUGHT AND AFTERTHOUGHT

13 Kotlin: The Next Step

PROGRAMMING KOTLIN FOR ANDROID

KOTLIN AND JAVA ARE GREAT COMPANIONS

WHEN KOTLIN QUESTIONS STILL EXIST

NOW WHAT