Objective c intro (1)

Overview  Objective-C is an object oriented language.  follows ANSI C style coding with methods from Smalltalk  Flexible almost everything is done at runtime. Dynamic Binding Dynamic Typing Dynamic Linking

Inventors  Objective-C was invented by two men, Brad Cox and Tom Love.  Both were introduced to Smalltalk at ITT in 1981  Cox thought something like Smalltalk would be very useful to application developers  Cox modified a C compiler and by 1983 he had a working Object-oriented extension to C called OOPC.

Development  Tom Love acquired a commercial copy of Smalltalk-80 while working for Schlumberger Research  With direct access Smalltalk, Love added more to OOPC making the final product, Objective-C.  In 1986 they release Objective-C through their company “Stepstone”

NeXT and NeXTSTEP  In 1988 Steve Jobs acquires Objective- C license for NeXT  Used Objective-C to build the NeXTSTEP Operating System  Objective-C made interface design for NeXTSTEP much easier  NeXTSTEP was derived from BSD Unix  In 1995 NeXT gets full rights to Objective-C from Stepstone

OPENSTEP API  Developed in 1993 by NeXT and Sun  An effort to make NeXTSTEP-like Objective-C implementation available to other platforms.  In order to be OS independent Removed dependency on Mach Kernel Made low-level data into classes  Paved the way for Mac OS X, GNUstep

Apple and Mac OS X  NeXT is taken over by Apple in 1996 and put Steve Jobs and his Objective-C libraries to work  Redesigned Mac OS to use objective-C similar to that of NeXTSTEP  Developed a collection of libraries named “Cocoa” to aid GUI development  Release Mac OS X (ten), which was radically different than OS 9, in March 2001

The Cocoa API  Developed by Apple from NeXTSTEP and OPENSTEP  Has a set of predefined classes and types such as NSnumber, NSstring, Nsdate, etc .  NS stands for NeXT-sun  Includes a root class NSObject where words like alloc, retain, and release come from

Dynamic Language  Almost everything is done at runtime  Uses dynamic typing, linking, and binding  This allows for greater flexibility  Minimizes RAM and CPU usage

To Import or Include?  C/C++’s #include will insert head.h into the code even if its been added before.  Obj-C’s #import checks if head.h has been imported beforehand. #import “head.h”

Objective-C  Is a SUPERSET of C

Primitive data types from C  int, short, long  float,double  char

Operators same as C  +  -  *  /  ++  --

Address and Pointers  Same as C  To get address of a variable i &i  Pointer int *addressofi = &I;

Conditionals and Loops  Same as C/C++  if / else if/ else  for  while  break  ontinue  do-while for(int i=0; i< 22; i++) { printf(“Checking i=“@dn”, i); if(i+90 == i*i) { break;}

for in loop  Introduced in Objective-C 2.0 (“fast enumeration”) for(Item_Type *item in Collection_of_Items) { //do whatever with the item Nslog(@” Looking now at %@”, item); } Note: %@ in the NSLog converts whatever is passed (in this case item) to a string

Functions  Same as C/C++  return_type functionName(type v1, type v2, ….) { //code of function } Example void showMeInfo(int age) { printf(“You are %d years old”, age); //or use NSLog() }

Global and static variables  Same as C/C++  Global variables defined at top of file  For static variables use keyword static before it static in CurrentYear = 2013;

Functions --- pass by reference  Same as C/C++ return_type functionName(type v1, type *v2, ….) { //code of function } Example – call above int v1 = 2; int v2 = 3; functionName(v1, &v2);

Main Funciton –like C++ #import <whatever/what.h> int main(int argc, const char *argv[]) { @autoreleasepool { //your code here******* //you can have C code if you wish or Objective-C return 0; } } NOTE: Latest version of Objective-C uses Automatic Reference Counting (kind of like automatic garbage collection) ----to handle getting rid of not needed items in memory (avoiding memory leaks). YEAH! AUTOMATIC! -----like Java this way @autoreleasepool in a needed annotation around your main block of code to “enable” this

IMPORTANT --- we are doing iOS applications NOT mac OS applications We will be doing iOS application that have a different framework called Model View Controller ---- But, for some examples to learn concepts of Objective-C we will show some basic main.m files with main functions that are not iOS programs!!! We will learn iOS soon!

Main Function –like C++ #import <whatever/what.h> int main(int argc, const char *argv[]) { @autoreleasepool { //takes care of “automatic release of not needed items //static method date with no parameters is invoked on NSDate class NSDate *now = [NSDate date]; //this will generate a new instance of NSDate with current time NSLog(@”The new date lives at %p”, now); //Objective-C function that is like printf to console double seconds = [now timeIntervalSince1970] //call timesInterrval* method on now object NSLog(@”It has been %f seconds since 1970”, seconds); NSDate *later = [now dateByAddingTimeInterval:100000]; //pass 100000 parameter to method NSLog(@”In 100,000 seconds will be %@”, later); //%@ means print as string return 0; } }

Non-GUI – text output  Two standard functions you see used  printf() – same as C ○ printf(“Hi Lynne”); //this is actual C code  NSLog() ○ NSLog(@”Hi Lynne”); //this is strictly Objective-C

Classes  Have both definition file and implementation file : classname.h and classname.m  Similar to how have .h and .cpp in C++

Declaring a class in ClassName.h#import <Cocoa/Cocoa.h> @interface ClassName : Parent { //class variables int age; NSString name; } // methods declared -(void)setAge:(int)number; -(void)setName:(NSString)n; -(int)getAge; -(NSString)getName; @end #import <standardimports.h> #import “local-your-otherfiles.h” @interface ClassName: Parent { //class variables } //methods -(return_type) methodName:(type)param1, (type) param2; @end

Declaring methods C++ syntax Objective-C syntax void function(int x, int y, char z); Object.function(x, y, z); -(void) method:(int)x, (int)y, (char)z; [Object function:x, y, z]; -(return type) function_name: (type) p1, (type) p2, ***;Apply function to Object passing parameters x,y,z

Whats this + and – stuff?  When declaring or implementing functions for a class, they must begin with a + or -  + indicates a “class method” that can only be used by the class itself. (they are like static methods in Java invoked on class itself)  - indicates “instance methods” to be used by the client program (public functions) –invoked on an object / class instance . (they are like regular methods in Java invoked on object)

Class Implementation File (ClassName.m) #import “ClassName.h” @implementation ClassName -(void)setAge:(int)number { age = number; } -(void)setName:(NSString)n { name = n; } -(int)getAge { return age; } -(NSString)getName { return name; } @end Remember our ClassName.h #import <Cocoa/Cocoa.h> @interface ClassName : Parent { //class variables int age; NSString name; } // methods declared -(void)setAge:(int)number; -(void)setName:(NSString)n; -(int)getAge; -(NSString)getName; @end

Class Declaration (Interface) #import <Cocoa/Cocoa.h> @interface Node : NSObject { Node *link; int contents; } +(id)new; -(void)setContent:(int)number; -(void)setLink:(Node*)next; -(int)getContent; -(Node*)getLink; @end Node.h Class is Node who’s parent is NSObject { class variables } +/- private/public methods of Class Class variables are private

Class Definition (Implementation) #import “Node.h” @implementation Node +(id)new { return [Node alloc];} -(void)setContent:(int)number {contents = number;} -(void)setLink:(Node*)next { [link autorelease]; link = [next retain]; } -(int)getContent {return contents;} -(Node*)getLink {return link;} @end Node.m Like your C++ .cpp file >>just give the methods here

Creating class instances ClassName *object = [[ClassName alloc] init]; ClassName *object = [[ClassName alloc] initWith* ];  NSString* myString = [[NSString alloc] init];  Nested method call. The first is the alloc method called on NSString itself. This is a relatively low-level call which reserves memory and instantiates an object. The second is a call to init on the new object. The init implementation usually does basic setup, such as creating instance variables. The details of that are unknown to you as a client of the class. In some cases, you may use a different version of init which takes input: ClassName *object = [ClassName method_to_create];  NSString* myString = [NSString string];  Some classes may define a special method that will in essence call alloc followed by some kind of init Creating an Object

Object ---invoking a method, the basics  Objective-C uses a Message Approach

Messages ---really weird (new) syntax  Almost every object manipulation is done by sending objects a message  Two words within a set of brackets, the object identifier and the message to send. Like C++ or Java’s Identifier.message() [Identifier message ]

Setting values for class variables of an object ---- THROUGH methods [object methodName]; [object setXXXMethod:value1]; [object setYYYYMethod:value2];

C++ VS. Objective-C  Adds OOP, metaprogramming and generic programming to C  Comes with a std library  Has numerous uses  Large and complex code for OOP  Only adds OOP to C  Has no standard library; is dependant on other libraries  Mostly used for application building  Simpler way of handling classes and objects

Keyword: id  The word ‘id’ indicates an identifier for an object much like a pointer in c++  This uses dynamic typing  For example, if Pen is a class… extern id Pen; id myPen; myPen = [Pen new ]; id work like pointers to objects.

Memory Allocation  Objects are created dynamically through the keyword, “alloc”  Objects are automatically deallocated in latest Objective-C through automatic reference counting

Automatic Reference Counting  Objective C uses ‘AUTOMATIC reference counting' as memory management  keeps an internal count of how many times an Object is 'needed'.  System makes sure that objects that are needed are not deleted, and when an object is not needed it is deleted.

iOS programs and @autoreleasepool  You will notice (later when you learn) your iOS applications are setup in Xcode (the IDE) with @autoreleasepool setup  This insures automatic release of unneeded items will take place for you.

linkList class #import "linkList.h" @implementation linkList +(id)new {return [linkList alloc];} -(void)insert:(int)value { id temp = [Node new]; [temp setContent:value]; [temp setLink:head]; head = [temp retain]; [temp release]; } -(void)append:(int)value { id last = [head getLink]; while ([last getLink] != nil) {last = [last getLink];} id temp = [Node new]; [temp setContent:value]; [last setLink:temp]; [temp release]; } -(void)remove { id temp = head; head = [head getLink]; [temp release]; } -(int)getValue { return [head getContent];} @end linkList.m Class linkList is child of previous Node class (not showing .h file for brevity)

Stack class (child of linkList) #import "linkList.h” @interface Stack : linkList {} +(id)new; -(void)push:(int)value; -(int)pop; @end #import "stack.h” @implementation Stack +(id)new {return [Stack alloc];} -(void)push:(int)value {[self insert:value];} -(int)pop { int ret = [self getValue]; //getValue metho of parent linkList [self remove]; //remove method of parent linkList return ret; } @end stack.h stack.m self is like the C++/Java word this. Remember alloc creates the object in memory

Example: main.m #import "stack.h” int main(){ Stack *s = [Stack new]; [s push:1]; [s push:2]; printf("%dt", [s pop]); [s push:3]; printf("%dt", [s pop]); printf("%dt", [s pop]); [s release]; return 0; } Run the program : 2 3 1 new is method defined in Stack class that simply that calls [Stack alloc] --- done for convinience Note only need to import “stack.h” because stack imports LinkList.h which imports Node.h which imports cocoa.h release is method to release this object s explicitly from memory

Primitive data types  int, short, long  float,double  char  BOOL = means boolean

NSInteger and NSUnteger NSInteger number; (Like long in C) NSUItneger another; (Like unsigned long in C) Objective-C data types that are 32-Bits on 32- Bit platforms and 64-bits on 64-bit platforms

NSString NSString *theMessage = @”hello world”; Number of characters in a string ○ NSUInteger charCount = [theMessage length]; Test if 2 strings equal ○ if([string_var_1 isEqual: string_var_2]) { //code for equal case }

String literal in Objective-C  Begins with the @ symbol  @”Lynne Grewe”; Some Examples NSString *myString = @”Hello World”; int len = [myString length]; OR int len = [@”Hello World” length]; OR NSString *myString = [[NSString alloc] initWithString:@”Hello World”]; int len = [myString length]; This is like “Lynne Grewe” in most other languages

Formatting Strings in output NSLog int a = 1; float b = 33.22; char c = ‘A’; NSLog(@”Integer %d Float: %f Char: %c”, a, b, c);

NSString ---not changeable  International (any language) strings using Unicode.  Compiler will create an NSString for you using @“foo” notation.  An NSString instance can not be modified! They are immutable.  Usual usage pattern is to send a message to an NSString and it will return you a new one.  self.display.text = [self.display.text stringByAppendingString:digit];  self.display.text = [NSString stringWithFormat:@“%g”, brain.operand]; // class method  Tons of utility functions available (case conversion, URLs, substrings, type conversions, etc.). Used throughout iOS instead of C language’s char * type.

NSMutableString ---changeable  Mutable version of NSString. Somewhat rarely used.  Can do some of the things NSString can do without creating a new one (i.e. in-place changes). NSMutableString *ms = [[NSMutableString alloc] initWithString:@“0.”]; NSMutableString *ms = [NSMutableString stringWithString:@“0.”]; // inherited from NSString [ms appendString:digit];

NSNumber  Object wrapper around primitive types like int, float, double, BOOL, etc. NSNumber *num = [NSNumber numberWithInt:36]; float f = [num floatValue]; // would return 36 as a float (i.e. will convert types)  Useful when you want to put multiple numeric primitive types in a collection (e.g. NSArray or NSDictionary).

NSValue  Generic object wrapper for other non- object data types. CGPoint point = CGPointMake(25.0, 15.0); // CGPoint is a C struct NSValue *pointObject = [NSValue valueWithCGPoint:point];

NSData  “Bag of bits.” Used to save/restore/transmit data throughout the iOS SDK.

NSDate  “Used to find out the time right now or to store past or future times/dates.  See also NSCalendar, NSDateFormatter, NSDateComponents.

NSArray – holds fixed array of points to objects NSArray *thearray = [NSArray arrayWithObjects:o1,o2,o3,o4, nil]; //get element [thearray objectAtIndex:0]; //element at index 0 Example NSDate *now = [NSDate date]; NSDate *tomorrow = [now dateByAddingTImeInterval:24.0*60.0*60.0]; //add a day NSDate *yesterday = [now dateByAddingTimeInterval:-24.0*60.0*60.0]; //minus a day //array of Dates NSArray *dateList = [NSArray arrayWithObjects:now, tomorrow, yesterday]; //get elements in array NSDate *first = [dateList objectAtIndex:0]; Methods are: count = gets number of items in array objectAtIndex:i = returns element i of array (starting from 0) Note: you can not add or remove a pointer from an NSArray ---fixed once created

NSArray – cycle through with for loop NSDate *now = [NSDate date]; NSDate *tomorrow = [now dateByAddingTImeInterval:24.0*60.0*60.0]; //add a day NSDate *yesterday = [now dateByAddingTimeInterval:-24.0*60.0*60.0]; //minus a day //array of Dates NSArray *dateList = [NSArray arrayWithObjects:now, tomorrow, yesterday]; //get elements in array NSDate *first = [dateList objectAtIndex:0]; NSUInteger dateCount = [dateList count]; for(int i=0; i<dateCount; i++) { NSDAte *d = [dateList objectAtIndex:i]; NSLog(@” Date is %@”, d); } Methods are: count = gets number of items in array objectAtIndex:i = returns element i of array (starting from 0)

NSArray – cycle through with for loop OPTION 2 NSDate *now = [NSDate date]; NSDate *tomorrow = [now dateByAddingTImeInterval:24.0*60.0*60.0]; //add a day NSDate *yesterday = [now dateByAddingTimeInterval:-24.0*60.0*60.0]; //minus a day //array of Dates NSArray *dateList = [NSArray arrayWithObjects:now, tomorrow, yesterday]; //get elements in array NSDate *first = [dateList objectAtIndex:0]; For(NSDate *d in dateList) { NSDAte *d = [dateList objectAtIndex:i]; NSLog(@” Date is %@”, d); } This is a “for in” loop --- convinient

NSMutableArray – changeable array of pointers to objects. NSMutableArray *thearray = [NSArray arrayWithObjects:o1,o2,o3,o4, nil]; //get element [thearray objectAtIndex:0]; //element at index 0 Example NSDate *now = [NSDate date]; NSDate *tomorrow = [now dateByAddingTImeInterval:24.0*60.0*60.0]; //add a day NSDate *yesterday = [now dateByAddingTimeInterval:-24.0*60.0*60.0]; //minus a day //array of Dates NSMutableArray *dateList = [NSMutableArray array]; //set elements [dateList addObject:now]; [dateList addObject:tomorrow]; [dateList addObject:yesterday]; Methods are: array = gets empty NSMutableArray addObject:obj = adds as next element the obj to array Note: you can add or remove a pointer from an NSMutableArray

NSMutableArray – adding element at Index location [arrayName insertObject:obj atIndex:i] Example -- put in at beginning of array [dateList insertObject:yesterday atIndex:0]

NSMutableArray – removing an element [arrayName removeObjectAtIndex:i] Example [dateList removeObjectAtIndex:0] //get rid of 1st element

NSDictionary  Immutable hash table. Look up objects using a key to get a value. + (id)dictionaryWithObjects:(NSArray *)values forKeys:(NSArray *)keys; + (id)dictionaryWithObjectsAndKeys:(id)firstObject, ...;  Creation example: NSDictionary *base = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:2], @“binary”, [NSNumber numberWithInt:16], @“hexadecimal”, nil];  Methods  - (int)count;  - (id)objectForKey:(id)key;  - (NSArray *)allKeys;  - (NSArray *)allValues;

NSMutableDictionary  Changeable + (id)dictionaryWithObjects:(NSArray *)values forKeys:(NSArray *)keys; + (id)dictionaryWithObjectsAndKeys:(id)firstObject, ...;  Creation : + (id)dictionary; //creates empty dictionary  Methods - (void)setObject:(id)anObject forKey:(id)key; - (void)removeObjectForKey:(id)key; - (void)removeAllObjects; - (void)addEntriesFromDictionary:(NSDictionary *)otherDictionary; see documentation (apple.com) for more details

NSMutableSet  Changeable version of NSSet  Methods - (void)addObject:(id)anObject; // does nothing if object that isEqual:anObject is already in - (void)removeObject:(id)anObject; - (void)unionSet:(NSSet *)otherSet; - (void)minusSet:(NSSet *)otherSet; - (void)intersectSet:(NSSet *)otherSet; see documentation (apple.com) for more details

Other useful Objective-C data classes  NSOrderedSet, NSMutableOrderedSet

Cycling through Collections classes ---- use for-in loop Example: NSArray of NSString NSArray *myArray = ...; for (NSString *string in myArray) { // no way for compiler to know what // myArray contains double value = [string doubleValue]; // crash HERE if string not an NSString }

NSSet example for-in loop Example: NSSet of id NSSet *mySet = ...; for (id obj in mySet) { // do something with obj, but make sure you //don’t send it a message it does not respond to if ([obj isKindOfClass:[NSString class]]) { // send NSString messages to obj with impunity } }

NSDictionary example for-in loop Example: NSDictionary NSDictionary *myDictionary = ...; for (id key in myDictionary) { // grab value associated with the current key id value = [myDictionary objectForKey:key]; // do something with value here *** }

Property list (plist)  A collection of collections  Specifically, it is any graph of objects containing only the following classes: ○ NSArray, NSDictionary, NSNumber, NSString, NSDate, NSData  Example1 : NSArray is a Property List if all its members are too --- NSArray of NSString is a Property List --- NSArray of NSArray as long as those NSArray’s members are Property Lists.  Example 2: NSDictionary is one only if all keys and values are too  Why define this term?  Because the SDK has a number of methods which operate on Property Lists.  Usually to read them from somewhere or write them out to somewhere.  [plist writeToFile:(NSString *)path atomically:(BOOL)]; // plist is NSArray or NSDictionary We will see this in practice later

NSUserDefaults  Lightweight storage of Property Lists.  an NSDictionary that persists between launches of your application.  Not a full-on database, so only store small things like user preferences.

NSUserDefaults continued  Read and write via a shared instance obtained via class method standardUserDefaults [[NSUserDefaults standardUserDefaults] setArray:rvArray forKey:@“RecentlyViewed”];  Methods (some) - (void)setDouble:(double)aDouble forKey:(NSString *)key; - (NSInteger)integerForKey:(NSString *)key; // NSInteger is a typedef to 32 or 64 bit int - (void)setObject:(id)obj forKey:(NSString *)key; // obj must be a Property List - (NSArray *)arrayForKey:(NSString *)key; // will return nil if value for key is not NSArray  Always remember to write the defaults out after each batch of changes! [[NSUserDefaults standardUserDefaults] synchronize];

CONCLUSION --- a note---Objective-C 2.0 – some features that were added  In October 2007, Apple Inc. releases Objective-C 2.0 for Mac OS 10.5 (Leopard)  Adds automatic garbage collection (ARC)  Instance Methods (public functions) are defined differently using @property ---see next lecture

Objective c intro (1)

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