enum {
   NSOrderedAscending = -1,
   NSOrderedSame,
   NSOrderedDescending
};
typedef NSInteger NSComparisonResult;

typedef struct _NSRange {
      NSUInteger location;   // start index
      NSUInteger length;     // location 위치부터의 길이 
} NSRange;

typedef double NSTimeInterval;

- (NSComparisonResult)compare:(NSString *)aString

- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

- (BOOL)isEqualToString:(NSString *)aString
 
- (BOOL)hasPrefix:(NSString *)aString

- (NSString *)stringByAppendingString:(NSString *)aString

- (NSString *)stringByAppendingFormat:(NSString *)format ...

- (NSString *)substringToIndex:(NSUInteger)anIndex

- (NSString *)substringFromIndex:(NSUInteger)anIndex

- (NSString *)substringWithRange:(NSRange)aRange

- (NSRange)rangeOfString:(NSString *)aString

- (NSRange)lineRangeForRange:(NSRange)aRange

- (NSString *)stringByReplacingCharactersInRange:(NSRange)range withString:(NSString *)replacement

- (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement

- (NSString *)capitalizedString

- (NSString *)lowercaseString

- (NSString *)uppercaseString

- (id)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding

- (const char *)cStringUsingEncoding:(NSStringEncoding)encoding

- (NSArray *)componentsSeparatedByCharactersInSet:(NSCharacterSet *)separator

- (NSArray *)componentsSeparatedByString:(NSString *)separator

- (void)performSelector:(SEL)aSelector withContext:(void*)context,... {
	if (context) {
		NSMethodSignature *signature = [self methodSignatureForSelector:aSelector];
		NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
		[invocation retainArguments];
		
		NSUInteger argumentCount = [signature numberOfArguments] - 2;
		
		[invocation setTarget:self];			// index 0
		[invocation setSelector:aSelector];	    // index 1
		
		va_list arguments;
		
		va_start(arguments, context);
		
		// 인자의 개수는 +2가 된 상태 
		NSUInteger i, count = argumentCount;
		void *currentValue = context;
		
		for (i = 0; i < count; i++) {
			[invocation setArgument:¤tValue atIndex:(i + 2)];
			currentValue = va_arg(arguments, void*); // 다음 인자 읽기 
		}
		
		va_end(arguments);
		
		NSThread *customWorkerThread = [NSThread currentThread];
		
		[invocation performSelector:@selector(invoke) onThread:customWorkerThread withObject:nil waitUntilDone:NO];
		
	} else {
		[self performSelectorInBackground:aSelector withObject:nil];
        
	}
}

// 호출할 메서드 
- (void)printArgument:(NSString*)arg1 andOther:(NSString*)arg2 andAnother:(NSString*)arg3 {
	NSLog(@"%@", [NSThread currentThread]);  
	NSLog(@"arg1: %@", arg1);
	NSLog(@"arg2: %@", arg2);
	NSLog(@"arg3: %@", arg3);
}

// 요렇게 호출할 수 있다. 깔끔하지 않는가? 
[self performSelector:@selector(printArgument:andOther:andAnother:) withContext:@"t1", @"t2", @"t3", nil];

#import "SuperClass.h"
@interface NewClass : SuperClass {
   int instanceVariable;
}
- method;
- methodWithParameter:param;

@end
@implementation NewClass

- method {
   return (nil);
}
- methodWithParameter:param {
   return (nil);
}

SpecificClass * specificObject;
id anyObject;

[object method];
[object methodWithParam:param];

objective-c에서는 메시지를 호출한다고 하기 보단, 객체에게 메세지를 보낸다고 한다. 

3. Naming Method

- valuePrepositionParameter:parameter
- objectForKey:key
- stringByAppendingString:string;
- numberFromString:string;

- (id)objectForKey:(id)aKey;
- (NSMenuItem)itemWithTag:(NSInteger)aTag;
- (unichar)characterAtIndex:(NSUInteger)index;
- (NSString*)stringByAddingPercentEscapeUsingEncoding:(NSStringEncoding)encoding;
- (void)runInNewThread;
- (void)addAttribute:(NSString*)name value:(id)value range:(NSRange)aRange;

SEL selector = @selector(fontWithFamily:traits:weight:size)

@interface RandomSequece : NSObject {
long long int seed;
}
+ (NSNumber*)number;
+ (NSNumber*)string;
- (NSNumber*)nextNumber;
- (NSString*)string;
@end
...
NSNumber *n = [RandomSequence number];
NSString *s = [RandomSequence string];

@interface Classy : NSObject {
   + (void)greeting;
+ (NSString*)salutation;
}
@end

@implementation
+ (void)greeting {
NSLog(@"%@, world!", [self salutation]);
 }
+ (NSString*)salutation {
NSLog(@"Greetings");
}
@end
@interface Classic : Classy
   + (NSString*)salutation;
@end
   + (NSString*)salutation {
     return (@"Hello");
}
@end
...
[Classy greeting];    // Logs "Greetings, world"
[Classic greeting];   // Logs "Hello, world!" 

@interface RandomSequence : NSObject {
long long seed;
}
- (id)init;
- (id)initWithSeed:(long long)startingSeed;
@end

@implementation RandomSequence
- (id)init {
self  = [super init];
if (self != nil) {  
   seed = 1;
}
return (self);
}
- (id)initWithSeed:(long long)startingSeed {
self = [super init];
if (self != nil) {
seed = startingSeed;
}
return (self);
}
@end
...
RandomSequence *r1 = [[RandomSequence alloc] init];
RandomSequence *r2 = [[RandomSequence alloc] initWithSeed:-43 ];
RandomSequence * r3 = [RandomSequence new];

- (void)finalize {
if (file != nil) {
[file close];
file = nil;
}
[super finalize]
}   

@interface NSData (ATOAuth) 
- (NSData*)dataByHmacSHA1EncryptingWithKey:(NSData*)key;
@end

#import "NSData+EOUtil.h"
#include <commoncrypto/commonhmac.h>

@implementation NSData (ATOAuth)

- (NSData*)dataByHmacSHA1EncryptingWithKey:(NSData*)key
{   
    void* buffer = malloc(CC_SHA1_DIGEST_LENGTH);
    CCHmac(kCCHmacAlgSHA1, [key bytes], [key length], [self bytes], [self length], buffer);
    return [NSData dataWithBytesNoCopy:buffer length:CC_SHA1_DIGEST_LENGTH freeWhenDone:YES];
}
@end