intro-to-objc2-0-pptx-100224025204-phpapp01

7/29/2019 intro-to-objc2-0-pptx-100224025204-phpapp01

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Introduc)ontoObjec)ve-C

JussiPohjolainen

TampereUniversityofAppliedSciences


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QUICKSTART


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Background

Objec)ve-CislayeredontopoftheClanguage

BasedonSmallTalk-80Designedinearly1980s

NeXTSoLwarelicensedObjec)ve-Cin1988 AppleComputeracquiredNeXTin1996 Today:na)velanguagefordevelopingMacOSX-andiPhone-apps


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ClassDeclara)on:MyPoint.h


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ClassImplementa)on:MyPoint.m


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TesttheClass:main.m


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Simplemakefile

MyPoint : MyPoint.m main.m

clang -fno-objc-arc -framework foundation

MyPoint.m main.m -o MyPoint

run :

./MyPoint

clean :

rm MyPoint


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CompilingandRunning

TB308POHJUS-L-2:point pohjus$ ls -altotal 32

drwxr-xr-x 6 pohjus staff 204 18 Tou 15:32 .

drwxr-xr-x 3 pohjus staff 102 18 Tou 14:52 ..

-rw-r--r--@ 1 pohjus staff 196 18 Tou 15:25 MyPoint.h

-rw-r--r--@ 1 pohjus staff 268 18 Tou 15:23 MyPoint.m

-rw-r--r--@ 1 pohjus staff 339 18 Tou 15:25 main.m

-rw-r--r--@ 1 pohjus staff 120 18 Tou 15:14 makefile

TB308POHJUS-L-2:point pohjus$ makeclang -fno-objc-arc -framework foundation MyPoint.m main.m -o MyPoint

TB308POHJUS-L-2:point pohjus$ make run./MyPoint

2009-05-18 15:32:46.339 MyPoint[8725:807] X = 0 and Y = 02009-05-18 15:32:46.341 MyPoint[8725:807] X = 8 and Y = 7

TB308POHJUS-L-2:point pohjus$


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Instan)a)nganObject

// Declare a pointer to the object

MyPoint* point;

// Allocate memory for the objectpoint = [MyPoint alloc];

// Initialize the object

point = [point init];


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Instan)a)nganObject:Oneiner

// Allocate and initialize the object

MyPoint* point1 = [[MyPoint alloc] init];


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Messages(Methods

- (void) setX: (int) n;!

methodtype:

+=classmethod

-=objectmethod

returntype selectorname

argumenttype

argument

name


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Messages,withTwoArguments

Declara=on

- (void) setXAndY: (int) x: (int) y

Usage

[object setXAndY: 5: 6];

Declara=on,be@erway

- (void) setX: (int) x andY: (int) yUsage

[object setX: 5 andY: 6];


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EXERCISES


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MEMORYMANAGEMENTANDOBJECT

LIFECYCLE


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MemoryHandlinginGeneral

WhenallocatesomethingitmustbereleasedMemoryconsump)on

InJava,garbagecollectortakescareoftherelease.Separatethreadlookingforobjectsthatcanbereleased

InObj-CandC/C++,programmerisresponsibleabouttherelease.


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AboutPointers

inta5;HoldsoneintegervalueTheintegerisstoredinsomememoryaddress

Where?Youcangetthememoryaddressbyusing&infrontofthevariable:&a


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ExampleofMemoryAddress

int main(int argc, char *argv[])

{

int a = 5;

// prints 5

NSLog(@"%i", a);// prints something like 0x7fff5fbff9cc

NSLog(@"%p", &a);return 0;

}


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Pointers

Pointerisavariablethatstoresmemoryaddress

inta;holdsintegervariable

int*b;holdsmemoryaddressthatpointstointegervalue

int*b&a;Nowbhasthememoryaddressofa


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ExampleaboutPointers

#import "MyPoint.h"


{

int a = 5;

// Store a's memory address to variable b

int *b = &a;

// prints 5

NSLog(@"%i", a);

// prints something like 0x7fff5fbff9cc

NSLog(@"%p", &a);

// prints something like 0x7fff5fbff9cc

NSLog(@"%p", b);

// prints 5

NSLog(@"%i", *b);

return 0;

}


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Whatistheresultnow?


{

int a = 5;

// Store a's memory address to variable b

int *b = &a;

if(b == &a)

{

NSLog(@"Do we go here?");

}

if(*b == a)

{

NSLog(@"What about here?");

}

return 0;

}


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Whatistheresultnow?


{

int a = 5;

int *b = &a;

*b = 10;

NSLog(@"%i", a);

return 0;}


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MemoryAreas

Memorycanbedividedintothreecategories1. Globalorsta)c2. Stack3. Heap


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Sta)c

Whensomethingisinsta)cmemory,it'sthereallthe)mewhenappisrunning

Sowhenstar)ngtheapp,thememoryisallocatedanwhentheappcloses,thememoryisdeallocated

Thevariableisstoredinthesamememoryaddressallthe)me.


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ExampleofSta)cMemory

int thisIsStoredInStaticMemory = 5;


{

static int thisIsAlsoStoredInStaticMemory = 10;

NSLog(@"My number = %i", thisIsStoredInStaticMemory);

NSLog(@"My number = %i", thisIsAlsoStoredInStaticMemory);

return 0;

}


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Stack-Memory

Stackmemoryareaisusuallysmall Ifyouputtoomuch"stuff"intostack,youmightgetstackoverflow

ocalvariablesarestoredinstack! Variablesarereleasedwhenoutofscope


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ExampleofStackMemory


{

int stack1 = 3;

NSLog(@"My number = %i", stack1);

if(YES){

int stack2 = 4;


// stack2 is released from memory now.}

// stack1 is released from memory now.return 0;

}


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ExampleofStackMemory


{

if(YES)

{

int stack2 = 4;}

// Does this work?


return 0;}


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Heap-Memory

Heapmemoryisthelargememoryareawherealmostalloftheobjectsgo.

Programmerisresponsibleforreleasingtheobjects!


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ExampleofHeap-memory

#import "MyPoint.h"


{

MyPoint* point = [MyPoint alloc];//...

[point release];

return 0;

}


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Crea)ngaObject

Thecrea)onofanobjectisdoneintwoparts 1Alloca)ngmemory

MyPoint* point = [MyPoint alloc];2Ini)alizeobjectstatepoint = [point init];

CombinedMyPoint* point = [[MyPoint alloc] init];

MyPoint* point = [MyPoint new];


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WhathappensinMemory?

Whathappensinhere?MyPoint* p = [MyPoint alloc];

Twothings!MyPoint* p;p = [MyPoint alloc];

pisinstackmemory!MyPointobjectisinheapmemory!


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Problem?

#import "MyPoint.h"


{

if(YES)

{MyPoint* point = [MyPoint alloc];

}

[point release];

return 0;

}


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Problem?

#import "MyPoint.h"


{

MyPoint* point = [MyPoint alloc];point = [MyPoint alloc];

[point release];

return 0;}


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init-method?

init-methodisimplementedinNSObject Youcanhoweverimplementyourowninit-method

- (id) initWithName: (NSString*) aName{

if(self = [super init])

{

name = aName;

}

return self;

}


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Otherinit-methods

ikeinJavaandC++,onecanhavemul)pleconstructors

InObj-C,onecanhavemul)pleinit-methods

- (id) init- (id) initWithX: (int) aX;- (id) initWithX: (int) aX andY: (int) aY


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DeallocingObjectandReferenceCount

Rulesaboutreferencecoun=ng Whenobjectiscreateditsreferencecountissetto1 Incremen)ngthereferencecount:

[point retain]; Decreasingreferencecount

[point release]; Whenreferencecountreachesto0,dealloca=ngoccurs

ARCwillsaveyoufromthis!


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ReferenceCountExample

#import

@interface Cat : NSObject

{

}

- (void) printMyRetainCount;

@end

@implementation Cat

- (void) printMyRetainCount

{NSLog(@"Retain count = %i", [self retainCount]);

}

@end


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{

Cat* myCat = [[Cat alloc] init];

[myCat printMyRetainCount]; // Retain count = 1

Cat* reference = myCat;

[reference retain];


[myCat release];


[myCat release]; // Deallocation

return 0;

}


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dealloc

Youcanimplementadeallocmethod(void) dealloc

{

// Some code

[super dealloc];

}


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#import


{

NSString* name;

}

- (void) setName: (NSString *) theName

@end

@implementation Cat


{name = theName;

}

@end


{

....

Cat* mirri = [[Cat alloc] init];

[mirri setName: someName];

// What happens now?[someName release];

}

Sincereferencecountis

0,dealloca)onoccurs.

Thismeans,thattheCat

doesnothaveaname

anymore.


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#import


{

NSString* name;

}


@end

@implementation Cat


{ [name release];name = theName;

[name retain];}

@end


{

....

Cat* mirri = [[Cat alloc] init];

[mirri setName: someName];

// What happens now?[someName release];

}

Sincereferencecountis

1,dealloca)ondoesnot

occurandtheCats)ll

hasit'sname.


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CopyingaObject

- (void)setName:(NSString *)theName

}

[name release];

name = [theName copy];}


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AutoreleasePool

EveryFounda)onprogrammustsetupautoreleasepoolfortheFounda)onobjects

Poolkeepstrackofyourobjectsforlaterrelease NSAutoreleasePool *pool = [[NSAutoreleasePoolalloc] init];

... [pool drain];


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MethodNames

Ifmethodnameincludesallocorcopy,itreturnsaobjectthatmustbereleased // Must be released NSObject* object = [[NSObject alloc] init]; // Must be released NSObject* copy = [object copy]; // Do not have to release NSMutableString* string = [NSMutableString string];

TheabovestringisreleasedinAutoreleasePool!


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Problem

// Programmer A code

[[someObject giveCat] eat];

// Programmer B code

- (Cat*) giveCat

{

// Must be released!


// But where? Should the programmer who calls this method be

// responsible for deallocation of the Cat? How does the programmer

// know this?return myCat;

}

..


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Solu)on

// Programmer A code

[[someObject giveCat] eat];

// Programmer B code

- (Cat*) giveCat

{



// But where? When autopool is drained!

[myCat autorelease];return myCat;

}


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DelayedRelease

Autoreleasemeans"sendreleasemessagelater".

ReleasemessageissentwhenAutoreleasePoolisreleased

AutoreleasePooliscreatedandreleasedinUIKitprogramsautoma=cally!

PooliscreatedatthebeginningofaneventcyclePoolisreleasedattheendofaneventcycle


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AutoreleasePools

Appoaded WaitforEvent Handleevent Exitapp

Eventloop

Pool

created

Pool

released


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AutoreleasePoolUsage

// Method

- (Cat*) giveCat

{



// But where? When autopool is drained!

[myCat autorelease];return myCat;

}

// Usage

Cat* someCat = [object giveCat];

// someCat will be released in some time, so if you want to hold it, use

// retain

[someCat retain];


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Rules

Ifmethodnamecontains"alloc","new"or"copy",youmustremembertouserelease

orautorelease

Example:alloc, newObject, mutableCopy Ifyouretain something,youmustuserelease orautorelease

InstanceVariables:retainorcopy autoreleasemeans"sendrelease later"


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Cat.h

#import


{

@privateNSString* name;

}

- (id) initWithName: (NSString*) aName;

- (void) setName: (NSString*) aName;

- (NSString*) getName;

- (void) dealloc;

@end


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Cat.m

#import "Cat.h"

@implementation Cat

- (id) initWithName: (NSString*) aName

{

if(self = [super init])

{

[self setName: aName];}

return self;

}

- (NSString*) getName

{

return name;

}

- (void) setName: (NSString*) aName

{

if(aName != name)

{

[name release];

name = aName;

[name retain];

}

}

- (void) dealloc

{

[name release];

[super dealloc];

}

@end


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main.m

#import "Cat.h"


{

NSAutoreleasePool *pool =[[NSAutoreleasePool alloc] init];

// Create the string

NSString* catName = [[NSStringalloc] initWithString: @"Jack"];

// Create cat with the string

Cat* cat = [[Cat alloc]initWithName: catName];

// Just testing. This does notdeallocate catName!

[catName release];

// Get the name

NSString* name = [cat getName];

// Print the name

NSLog(name);

// Release name and cat

[cat release];

[pool drain];

return 0;

}


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MANAGINGMEMORYWITHARC

ARCtotherescue!


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ARC?

ARC(Automa=cReferenceCoun=ng)Compilerdoesautoma/creferencecoun/ngbyexaminingthesourcecodeandthenaddtheretainandreleasemessagestoobjects

Notgarbagecollec)on,nobackgroundprocessofdealloca)onofobjects!

Insertsretainandreleasestatementsbasedonsomefixedrules

OSX10.7andiOS5forallfeatures


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Objectloseowners

// Scenario 1

Person* jack = [[Person alloc] init];

jack = [[Person alloc] init];

// Scenario 2

Person* tina = [[Person alloc] init];

tina = nil;

// Scenario 3

if(yes) {

Person* dave = [[Person alloc]init];}


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SomeFixedrules

Ifobjectisallocatedandlocaltomethod,releasestatementisaddedneartheendof

thatmethod

Ifallocatedobjectisclassa@ribute,releaseisaddedtodealloc Iftheobjectisreturnvalue,itgetsanautoreleasestatement


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Guidelines

Dontcall!retain, release, retainCount, autoreleaseor dealloc

Youmustuseautoreleasepoolsyntax YoumustenableARC

clang -fobjc-arc -framework foundationCar.m Motor.m main.m -o App


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makefile

MyPoint : Car.m Motor.m main.m

clang -fobjc-arc -framework foundation Car.m Motor.m main.m

-o App

run :

./App

clean :

rm App


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main.m


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motor.h


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motor.m


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car.h


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car.m


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PROPERTIES


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Objec)ve-C2.0:@property


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Objec)ve-C2.0:@synthesize


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Objec)ve-C2.0:DotSyntax


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Autosynthesize


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Autosynthesize


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PropertyDeclara)onAributes:

Writability

Youcandecorateapropertywithaributes,example:

@property (readonly) int x; readwrite

Indicatesthatthepropertyisread/write.Default readonly

OnlyreadGeneratesonlygeermethod


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SeerSeman)cs

assignSimpleseer.Default.

weakNon-owningrela)onshipwithanobject Ifobjectisdeallocated,thepropertyissettonil

strongOwningrela)onshipwithanobject

copySpecifiesthatacopyoftheobjectshouldbeusedforassignment


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SeerSeman)csExamples

// assignproperty = newValue;

// copyif (property != newValue)

{

[property release];

property = [newValue copy];

}


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Atomicity

nonatomicSpecifiesthataccessorarenon-atomic.

Proper)esareatomicbydefault:[_internal lock];id result = [[value retain] autorelease];[_internal unlock];return id;


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Car.h


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Motor.h


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Main.m


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Change!Car.h


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STRINGS


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AboutStrings

CStringchar * // Array of characters

NSStringObject,thatholdsarrayofUnicodecharactersIsimmutable,contentscannotbechangedaLerwards!

NSMutableStringStringthatcanbemodifiedaLerwards


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Formang

Formang NSString *string1 = [NSString stringWithFormat:@"A

string: %@, a float: %1.2f",@"string", 31415.9265]; // string1 is "A string: string, a float: 31415.93"

FormatSpecifiers?http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/

Strings/Articles/formatSpecifiers.html#//

apple_ref/doc/uid/TP40004265-SW1


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NSMutableString methods

NSMutableString inheritesNSString WithNSMutableString youcanmodifythestringwiththesemethods

appendFormat:appendString:deleteCharactersInRange:insertString:atIndex:replaceCharactersInRange:withString:replaceOccurrencesOfString:withString:options:range:setString:


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PROTOCOLS


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Protocols?

ComparedtoJava,protocolsareinterfaces Youdefinemethodsthatsomeobjectmustimplement


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UsingProtocols

// MyProtocolName.h

// Notice that the protocol inherites NSObject

// protocol!

@protocol MyProtocolName //Method declarations go here@end

// MyObject

@interface Class: NSObject


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ProtocolasVariable

InJavaMyInterface object = new MyObject();

InObj-Cid object = [[MyObjectalloc] init];

Asamethodargument(void) doSomethingWithThisObject:(id) aObject

IDisapredefinedpointertypeforanarbitraryobject


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FOUNDATIONCLASSES


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NSObject

NSObjectistherootclassofMostObj-Cclasses

Crea)ng,copying,dealloca)ngobjects


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Collec)ons

Array:OrderedCollec/ons Dic)onary:Collec/onsofKeysandValues Set:UnorderedCollec/onsofObjects CountedSets:UnorderedCollec/onofIndis/nctObjects

Enumera)on:TraversingaCollec/on'sElements

Mutableandimmutableversions!


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OtherClasses

NSNumber,wrapperforstandardnumbertypes

NSDate,NSCalendarDate

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