@interface EOCPerson : NSObject

@property NSString *firstName;
@property NSString *lastName;
@end


@interface EOCPerson : NSObject

- (NSString*)firstName;
- (void)setFirstName:(NSString*)firstName;
- (NSString*)lastName;
- (void)setLastName:(NSString*)lastName;

@end

aPerson.firstName = @"Bob"; // Same as:
[aPerson setFirstName:@"Bob"];

NSString *lastName = aPerson.lastName; // Same as:
NSString *lastName = [aPerson lastName];

@interface EOCPerson : NSManagedObject
@property NSString *firstName;
@property NSString *lastName;
@end

@implementation EOCPerson
@dynamic firstName, lastName;
@end

- (id)initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName {
         if ((self = [super init])) {
            _firstName = [firstName copy];
            _lastName = [lastName copy];
        }
       return self;
}

- (BOOL)isEqualToPerson:(EOCPerson*)otherPerson {
     //先比较对象类型，然后比较每个属性
     if (self == object) return YES;
     if (![_firstName isEqualToString:otherPerson.firstName])
         return NO;
     if (![_lastName isEqualToString:otherPerson.lastName])
         return NO;
     if (_age != otherPerson.age)
         return NO;
     return YES;
}

- (BOOL)isEqual:(id)object {
    //如果对象所属类型相同，就调用自己编写的判定方法，如果不同，调用父类的isEqual:方法
     if ([self class] == [object class]) {    
         return [self isEqualToPerson:(EOCPerson*)object];
    } else {    
         return [super isEqual:object];
    }
}

id returnValue = [someObject messageName:parameter];

void objc_msgSend(id self, SEL cmd, ...)

id returnValue = objc_msgSend(someObject,@selector(messageName:),parameter);

#import <Foundation/Foundation.h>

@interface EOCAutoDictionary : NSObject
@property (nonatomic, strong) NSString *string;
@property (nonatomic, strong) NSNumber *number;
@property (nonatomic, strong) NSDate *date;
@property (nonatomic, strong) id opaqueObject;
@end

#import "EOCAutoDictionary.h"
#import <objc/runtime.h>
@interface EOCAutoDictionary ()
@property (nonatomic, strong) NSMutableDictionary *backingStore;
@end

@implementation EOCAutoDictionary

@dynamic string, number, date, opaqueObject;

- (id)init {
 if ((self = [super init])) {
    _backingStore = [NSMutableDictionary new];
}
   return self;
}

+ (BOOL)resolveInstanceMethod:(SEL)selector {
     NSString *selectorString = NSStringFromSelector(selector);
     if ([selectorString hasPrefix:@"set"]) {
         class_addMethod(self,selector,(IMP)autoDictionarySetter, "v@:@");
     } else {
         class_addMethod(self,selector,(IMP)autoDictionaryGetter, "@@:");
    }
     return YES;
}

id autoDictionaryGetter(id self, SEL _cmd) {

     // Get the backing store from the object
     EOCAutoDictionary *typedSelf = (EOCAutoDictionary*)self;
     NSMutableDictionary *backingStore = typedSelf.backingStore;

     // The key is simply the selector name
     NSString *key = NSStringFromSelector(_cmd);

     // Return the value
     return [backingStore objectForKey:key];
}

复制代码

void autoDictionarySetter(id self, SEL _cmd, id value) {
     // Get the backing store from the object
     EOCAutoDictionary *typedSelf = (EOCAutoDictionary*)self;
     NSMutableDictionary *backingStore = typedSelf.backingStore;

     /** The selector will be for example, "setOpaqueObject:".
     * We need to remove the "set", ":" and lowercase the first
     * letter of the remainder.
     */
     NSString *selectorString = NSStringFromSelector(_cmd);
     NSMutableString *key = [selectorString mutableCopy];

     // Remove the ':' at the end
    [key deleteCharactersInRange:NSMakeRange(key.length - 1, 1)];

     // Remove the 'set' prefix
    [key deleteCharactersInRange:NSMakeRange(0, 3)];

     // Lowercase the first character
     NSString *lowercaseFirstChar = [[key substringToIndex:1] lowercaseString];
    [key replaceCharactersInRange:NSMakeRange(0, 1) withString:lowercaseFirstChar];

     if (value) {
       [backingStore setObject:value forKey:key];
    } else {
        [backingStore removeObjectForKey:key];        
    }
}

typedef struct objc_class *Class;
    struct objc_class {
         Class isa;
         Class super_class;
         const char *name;
         long version;
         long info;
         long instance_size;
         struct objc_ivar_list *ivars;
         struct objc_method_list **methodLists;
         struct objc_cache *cache;
         struct objc_protocol_list *protocols;
};

- (NSString*)commaSeparatedStringFromObjects:(NSArray*)array {
         NSMutableString *string = [NSMutableString new];
             for (id object in array) {
                    if ([object isKindOfClass:[NSString class]]) {
                            [string appendFormat:@"%@,", object];
                    } else if ([object isKindOfClass:[NSNumber class]]) {
                            [string appendFormat:@"%d,", [object intValue]];
                    } else if ([object isKindOfClass:[NSData class]]) {
                           NSString *base64Encoded = /* base64 encoded data */;
                            [string appendFormat:@"%@,", base64Encoded];
                    } else {
                            // Type not supported
                    }
              }
             return string;
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

- (BOOL)doSomething:(NSError**)error

NSError *error = nil;
BOOL ret = [object doSomething:&error];

if (error) {
    // There was an error
}

 // EOCErrors.h
    extern NSString *const EOCErrorDomain;
    
    //定义错误码
    typedef NS_ENUM(NSUInteger, EOCError) {
    
        EOCErrorUnknown = –1,
        EOCErrorInternalInconsistency = 100,
        EOCErrorGeneralFault = 105,
        EOCErrorBadInput = 500,
    };

    // EOCErrors.m
    NSString *const EOCErrorDomain = @"EOCErrorDomain"; //定义错误范围

- (id)copyWithZone:(NSZone*)zone

- (id)copyWithZone:(NSZone*)zone {
     EOCPerson *copy = [[[self class] allocWithZone:zone] initWithFirstName:_firstName  andLastName:_lastName];
    copy->_friends = [_friends mutableCopy];
     return copy;
}

- (id)mutableCopyWithZone:(NSZone*)zone；

-[NSMutableArray copy] => NSArray
-[NSArray mutableCopy] => NSMutableArray

- (id)initWithSet:(NSArray*)array copyItems:(BOOL)copyItems;

- (id)deepCopy {
       EOCPerson *copy = [[[self class] alloc] initWithFirstName:_firstName andLastName:_lastName];
        copy->_friends = [[NSMutableSet alloc] initWithSet:_friends copyItems:YES];
        return copy;
}

- (NSString*)stringValue {
     NSString *str = [[NSString alloc] initWithFormat:@"I am this: %@", self];
     return [str autorelease];
}

if ([self shouldLogMessage]) {
     NSString *message = [[NSString alloc] initWithFormat:@"I am object, %p", self];
     NSLog(@"message = %@", message);
      [message release]; ///< Added by ARC
}

void (^block)();

if ( /* some condition */ ) {
    block = ^{
     NSLog(@"Block A");
    };

} else {
    block = ^{
     NSLog(@"Block B");
    };
}

block();

void (^block)();

if ( /* some condition */ ) {
    block = [^{
         NSLog(@"Block A");
   } copy];
} else {
    block = [^{
         NSLog(@"Block B");
    } copy];
}

block();

void (^block)() = ^{
     NSLog(@"This is a block");
};

// EOCPerson.h
#import <Foundation/Foundation.h>

@class EOCEmployer;

@interface EOCPerson : NSObject

@property (nonatomic, copy) NSString *firstName;
@property (nonatomic, copy) NSString *lastName;
@property (nonatomic, strong) EOCEmployer *employer;//将EOCEmployer作为属性

@end

// EOCPerson.m
#import "EOCEmployer.h"

NSNumber *intNumber = @1;
NSNumber *floatNumber = @2.5f;

NSArray *animals =[NSArray arrayWithObjects:@"cat", @"dog",@"mouse", @"badger", nil];
Dictionary *dict = @{@"animal":@"tiger",@"phone":@"iPhone 6"};

NSString *cat = animals[0];
NSString *iphone = dict[@"phone"];

//header file
extern NSString *const NotificationString;

//implementation file
NSString *const  NotificationString = @"Finish Download";

typedef NS_ENUM(NSUInteger, EOCConnectionState) {
  EOCConnectionStateDisconnected,
  EOCConnectionStateConnecting,
  EOCConnectionStateConnected,
};

@interface EOCPerson : NSObject

@property (nonatomic, copy, readonly) NSString *firstName;
@property (nonatomic, copy, readonly) NSString *lastName;
@property (nonatomic, strong, readonly) NSSet *friends //向外公开的不可变集合

- (id)initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName;
- (void)addFriend:(EOCPerson*)person;
- (void)removeFriend:(EOCPerson*)person;

@end

@interface EOCPerson ()

@property (nonatomic, copy, readwrite) NSString *firstName;
@property (nonatomic, copy, readwrite) NSString *lastName;

@end

@implementation EOCPerson {
     NSMutableSet *_internalFriends;  //实现文件里的可变集合
}

- (NSSet*)friends {
     return [_internalFriends copy]; //get方法返回的永远是可变set的不可变型
}

- (void)addFriend:(EOCPerson*)person {
    [_internalFriends addObject:person]; //在外部增加集合元素的操作
    //do something when add element
}

- (void)removeFriend:(EOCPerson*)person {
    [_internalFriends removeObject:person]; //在外部移除元素的操作
    //do something when remove element
}

- (id)initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName {

     if ((self = [super init])) {
        _firstName = firstName;
        _lastName = lastName;
        _internalFriends = [NSMutableSet new];
    }
 return self;
} 

- (NSSet*)friends {
    return [_internalFriends copy];
}

//方法定义
- (id)initWithSize:(float)width :(float)height;

//方法调用
EOCRectangle *aRectangle =[[EOCRectangle alloc] initWithSize:5.0f :10.0f];

//方法定义
- (id)initWithWidth:(float)width height:(float)height;

//方法调用
EOCRectangle *aRectangle =[[EOCRectangle alloc] initWithWidth:5.0f height:10.0f];

- hasPrefix:

#import <Foundation/Foundation.h>

@interface EOCObject : NSObject

- (void)publicMethod;

@end


@implementation EOCObject

- (void)publicMethod {
 /* ... */
}

- (void)p_privateMethod {
 /* ... */
}

@end

NSData *data = /* data obtained from network */;

if ([_delegate respondsToSelector: @selector(networkFetcher:didReceiveData:)])
{
        [_delegate networkFetcher:self didReceiveData:data];
}

NSData *data = /* data obtained from network */;

if ( (_delegate) && ([_delegate respondsToSelector: @selector(networkFetcher:didReceiveData:)]))
{
        [_delegate networkFetcher:self didReceiveData:data];
}

#import <Foundation/Foundation.h>

@interface EOCPerson : NSObject

@property (nonatomic, copy, readonly) NSString *firstName;
@property (nonatomic, copy, readonly) NSString *lastName;
@property (nonatomic, strong, readonly) NSArray *friends;

- (id)initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName;

/* Friendship methods */
- (void)addFriend:(EOCPerson*)person;
- (void)removeFriend:(EOCPerson*)person;
- (BOOL)isFriendsWith:(EOCPerson*)person;


/* Work methods */
- (void)performDaysWork;
- (void)takeVacationFromWork;


/* Play methods */
- (void)goToTheCinema;
- (void)goToSportsGame;
@end

#import <Foundation/Foundation.h>
@interface EOCPerson : NSObject
@property (nonatomic, copy, readonly) NSString *firstName;
@property (nonatomic, copy, readonly) NSString *lastName;
@property (nonatomic, strong, readonly) NSArray *friends;

- (id)initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName;

@end

@interface EOCPerson (Friendship)

- (void)addFriend:(EOCPerson*)person;
- (void)removeFriend:(EOCPerson*)person;
- (BOOL)isFriendsWith:(EOCPerson*)person;

@end

@interface EOCPerson (Work)

- (void)performDaysWork;
- (void)takeVacationFromWork;

@end

@interface EOCPerson (Play)

- (void)goToTheCinema;
- (void)goToSportsGame;

@end

// EOCPerson+Friendship.h
#import "EOCPerson.h"


@interface EOCPerson (Friendship)

- (void)addFriend:(EOCPerson*)person;
- (void)removeFriend:(EOCPerson*)person;
- (BOOL)isFriendsWith:(EOCPerson*)person;

@end


// EOCPerson+Friendship.m
#import "EOCPerson+Friendship.h"


@implementation EOCPerson (Friendship)

- (void)addFriend:(EOCPerson*)person {
 /* ... */
}

- (void)removeFriend:(EOCPerson*)person {
 /* ... */
}

- (BOOL)isFriendsWith:(EOCPerson*)person {
 /* ... */
}

@end

@interface NSString (ABC_HTTP)

// Encode a string with URL encoding
- (NSString*)abc_urlEncodedString;

// Decode a URL encoded string
- (NSString*)abc_urlDecodedString;

@end

- (void)dealloc {
     CFRelease(coreFoundationObject);
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

NSArray *anArray = /* ... */;
for (int i = 0; i < anArray.count; i++) {
   id object = anArray[i];
   // Do something with 'object'
}

// Dictionary
NSDictionary *aDictionary = /* ... */;
NSArray *keys = [aDictionary allKeys];
for (int i = 0; i < keys.count; i++) {
   id key = keys[i];
   id value = aDictionary[key];
   // Do something with 'key' and 'value'
}

// Set
NSSet *aSet = /* ... */;
NSArray *objects = [aSet allObjects];
for (int i = 0; i < objects.count; i++) {
   id object = objects[i];
   // Do something with 'object'
}

NSArray *anArray = /* ... */;
for (id object in anArray) {
 // Do something with 'object'
}

// Dictionary
NSDictionary *aDictionary = /* ... */;
for (id key in aDictionary) {
 id value = aDictionary[key];
 // Do something with 'key' and 'value'

}


NSSet *aSet = /* ... */;
for (id object in aSet) {
 // Do something with 'object'
}

NSArray *anArray = /* ... */;
[anArray enumerateObjectsUsingBlock:^(id object, NSUInteger idx, BOOL *stop){
   // Do something with 'object'
   if (shouldStop) {
      *stop = YES; //使迭代停止
  }

}];


“// Dictionary
NSDictionary *aDictionary = /* ... */;
[aDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id object, BOOL *stop){
     // Do something with 'key' and 'object'
     if (shouldStop) {
        *stop = YES;
    }
}];


// Set
NSSet *aSet = /* ... */;
[aSet enumerateObjectsUsingBlock:^(id object, BOOL *stop){
     // Do something with 'object'
     if (shouldStop) {
        *stop = YES;
    }

for (NSString *key in aDictionary) {
         NSString *object = (NSString*)aDictionary[key];
        // Do something with 'key' and 'object'
}

NSDictionary *aDictionary = /* ... */;

    [aDictionary enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *obj, BOOL *stop){

             // Do something with 'key' and 'obj'

}];

// Network fetcher class
typedef void(^EOCNetworkFetcherCompletionHandler)(NSData *data);

@interface EOCNetworkFetcher : NSObject

- (id)initWithURL:(NSURL*)url;
- (void)startWithCompletionHandler:(EOCNetworkFetcherCompletionHandler)handler;

@end

// Class that uses the network fetcher and caches results
@interface EOCClass : NSObject
@end

@implementation EOCClass {
     NSCache *_cache;
}

- (id)init {

     if ((self = [super init])) {
    _cache = [NSCache new];

     // Cache a maximum of 100 URLs
    _cache.countLimit = 100;


     /**
     * The size in bytes of data is used as the cost,
     * so this sets a cost limit of 5MB.
     */
    _cache.totalCostLimit = 5 * 1024 * 1024;
    }
 return self;
}



- (void)downloadDataForURL:(NSURL*)url { 

     NSData *cachedData = [_cache objectForKey:url];

     if (cachedData) {

         // Cache hit：存在缓存，读取
        [self useData:cachedData];

    } else {

         // Cache miss：没有缓存，下载
         EOCNetworkFetcher *fetcher = [[EOCNetworkFetcher alloc] initWithURL:url];      

        [fetcher startWithCompletionHandler:^(NSData *data){
         [_cache setObject:data forKey:url cost:data.length];    
        [self useData:data];
        }];
    }
}
@end

- (void)downloadDataForURL:(NSURL*)url { 

      NSPurgeableData *cachedData = [_cache objectForKey:url];

      if (cachedData) {         

            // 如果存在缓存，需要调用beginContentAccess方法
            [cacheData beginContentAccess];

             // Use the cached data
            [self useData:cachedData];

             // 使用后，调用endContentAccess
            [cacheData endContentAccess];


        } else {

                 //没有缓存
                 EOCNetworkFetcher *fetcher = [[EOCNetworkFetcher alloc] initWithURL:url];    

                  [fetcher startWithCompletionHandler:^(NSData *data){                         NSPurgeableData *purgeableData = [NSPurgeableData dataWithData:data];
                         [_cache setObject:purgeableData forKey:url cost:purgeableData.length];

                          // Don't need to beginContentAccess as it begins            
                          // with access already marked
                           // Use the retrieved data
                            [self useData:data];

                             // Mark that the data may be purged now
                            [purgeableData endContentAccess];

            }];
      }
}

+(void)load;

+(void)initialize;

#import <Foundation/Foundation.h>

@interface EOCBaseClass : NSObject
@end

@implementation EOCBaseClass
+ (void)initialize {
 NSLog(@"%@ initialize", self);
}
@end

@interface EOCSubClass : EOCBaseClass
@end

@implementation EOCSubClass
@end

EOCBaseClass initialize
EOCSubClass initialize

+ (void)initialize {
   if (self == [EOCBaseClass class]) {
       NSLog(@"%@ initialized", self);
    }
}

#import <Foundation/Foundation.h>

@interface EOCClass : NSObject
- (void)startPolling;
- (void)stopPolling;
@end


@implementation EOCClass {
     NSTimer *_pollTimer;
}


- (id)init {
     return [super init];
}


- (void)dealloc {
    [_pollTimer invalidate];
}


- (void)stopPolling {

    [_pollTimer invalidate];
    _pollTimer = nil;
}


- (void)startPolling {
   _pollTimer = [NSTimer scheduledTimerWithTimeInterval:5.0
                                                 target:self
                                               selector:@selector(p_doPoll)
                                               userInfo:nil
                                                repeats:YES];
}

- (void)p_doPoll {
    // Poll the resource
}

@end

#import <Foundation/Foundation.h>

@interface NSTimer (EOCBlocksSupport)

+ (NSTimer*)eoc_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
                                         block:(void(^)())block
                                         repeats:(BOOL)repeats;
@end



@implementation NSTimer (EOCBlocksSupport)

+ (NSTimer*)eoc_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
                                         block:(void(^)())block
                                        repeats:(BOOL)repeats
{
             return [self scheduledTimerWithTimeInterval:interval
                                                  target:self
                                                selector:@selector(eoc_blockInvoke:)
                                                userInfo:[block copy]
                                                 repeats:repeats];

}


+ (void)eoc_blockInvoke:(NSTimer*)timer {
     void (^block)() = timer.userInfo;
         if (block) {
             block();
        }
}
@end

- (void)startPolling {

         __weak EOCClass *weakSelf = self;    
         _pollTimer = [NSTimer eoc_scheduledTimerWithTimeInterval:5.0 block:^{

               EOCClass *strongSelf = weakSelf;
               [strongSelf p_doPoll];
          }

                                                          repeats:YES];
}

+ (UIButton *)buttonWithType:(UIButtonType)type;

//EOCEmployee.h

typedef NS_ENUM(NSUInteger, EOCEmployeeType) {
    EOCEmployeeTypeDeveloper,
    EOCEmployeeTypeDesigner,
    EOCEmployeeTypeFinance,
};

@interface EOCEmployee : NSObject

@property (copy) NSString *name;
@property NSUInteger salary;


// Helper for creating Employee objects
+ (EOCEmployee*)employeeWithType:(EOCEmployeeType)type;

// Make Employees do their respective day's work
- (void)doADaysWork;

@end


//EOCEmployee.m

@implementation EOCEmployee

+ (EOCEmployee*)employeeWithType:(EOCEmployeeType)type {
     switch (type) {
         case EOCEmployeeTypeDeveloper:
            return [EOCEmployeeDeveloper new];
         break; 

        case EOCEmployeeTypeDesigner:
             return [EOCEmployeeDesigner new];
         break;

        case EOCEmployeeTypeFinance:
             return [EOCEmployeeFinance new];
         break;
    }
}

- (void)doADaysWork {
 // 需要子类来实现
}

@end

@interface EOCEmployeeDeveloper : EOCEmployee
@end

@implementation EOCEmployeeDeveloper

- (void)doADaysWork {
    [self writeCode];
}

@end

#import <objc/runtime.h>
static void *EOCMyAlertViewKey = "EOCMyAlertViewKey";

- (void)askUserAQuestion {

         UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Question"
                                                         message:@"What do you want to do?"
                                                        delegate:self
                                               cancelButtonTitle:@"Cancel"
                                               otherButtonTitles:@"Continue", nil];

         void (^block)(NSInteger) = ^(NSInteger buttonIndex){

                     if (buttonIndex == 0) {
                            [self doCancel];
                     } else {
                            [self doContinue];
                    }
         };

         //将alert和block关联在了一起
         objc_setAssociatedObject(alert,EOCMyAlertViewKey,block, OBJC_ASSOCIATION_COPY);
         [alert show];
}

// UIAlertViewDelegate protocol method
- (void)alertView:(UIAlertView*)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
     //alert取出关联的block
      void (^block)(NSInteger) = objc_getAssociatedObject(alertView, EOCMyAlertViewKey)
     //给block传入index值
      block(buttonIndex);
}

Method originalMethod = class_getInstanceMethod([NSString class], @selector(lowercaseString));
Method swappedMethod = class_getInstanceMethod([NSString class],@selector(uppercaseString));

method_exchangeImplementations(originalMethod, swappedMethod);

@interface NSString (EOCMyAdditions)
- (NSString*)eoc_myLowercaseString;
@end


@implementation NSString (EOCMyAdditions)

- (NSString*)eoc_myLowercaseString {
     NSString *lowercase = [self eoc_myLowercaseString];//eoc_myLowercaseString方法会在将来方法调换后执行lowercaseString的方法
     NSLog(@"%@ => %@", self, lowercase);//输出语句，便于调试
     return lowercase;
}
@end

Method originalMethod =
 class_getInstanceMethod([NSString class],
 @selector(lowercaseString));
Method swappedMethod =
 class_getInstanceMethod([NSString class],
 @selector(eoc_myLowercaseString));

method_exchangeImplementations(originalMethod, swappedMethod);

“NSString *string = @"ThIs iS tHe StRiNg";
NSString *lowercaseString = [string lowercaseString];
// Output: ThIs iS tHe StRiNg => this is the string”

   //全能初始化方法
    - (id)initWithWidth:(float)width andHeight:(float)height
    {
         if ((self = [super init])) {
            _width = width;
            _height = height;
        }
        return self;
    }
    
    //init方法也调用了全能初始化方法
    - (id)init {
         return [self initWithWidth:5.0f andHeight:10.0f];
    }

- (id)initWithDimension: (float)dimension{
    return [super initWithWidth:dimension andHeight:dimension];
}

- (id)initWithWidth:(float)width andHeight:(float)height
{
    float dimension = MAX(width, height);
    return [self initWithDimension:dimension];
}

- (id)init{
    return [self initWithDimension:5.0f];
}

// Initializer from NSCoding
- (id)initWithCoder:(NSCoder*)decoder {

     // Call through to super's designated initializer
         if ((self = [super init])) {
            _width = [decoder decodeFloatForKey:@"width"];
            _height = [decoder decodeFloatForKey:@"height"];
        }
     return self;
}

// Initializer from NSCoding
- (id)initWithCoder:(NSCoder*)decoder {

 // Call through to super's designated initializer
      if ((self = [super initWithCoder:decoder])) {
     // EOCSquare's specific initializer
    }
     return self;
}

object = <EOCPerson: 0x7fd9a1600600>

- (NSString*)description {
     return [NSString stringWithFormat:@"<%@: %p, %@ %@>", [self class], self, firstName, lastName];
}

- (NSString*)description {
     return [NSString stringWithFormat:@"<%@: %p, %@>",[self class],self,
   
    @{    @"title":_title,
       @"latitude":@(_latitude),
      @"longitude":@(_longitude)}
    ];
}

location = <EOCLocation: 0x7f98f2e01d20, {

    latitude = "51.506";
   longitude = 0;
       title = London;
}>

@property (nonatomic, weak) id <EOCDelegate> delegate;

- (void)setObject:(id)object forKey:(id<NSCopying>)key;

@try {
     EOCSomeClass *object = [[EOCSomeClass alloc] init];
      [object doSomethingThatMayThrow];
      [object release];
}

@catch (...) {
         NSLog(@"Whoops, there was an error. Oh well...");
}

EOCSomeClass *object;
@try {
    object = [[EOCSomeClass alloc] init];
    [object doSomethingThatMayThrow];
}

@catch (...) {
     NSLog(@"Whoops, there was an error. Oh well...");
}

@finally {
    [object release];
}

@try {
     EOCSomeClass *object = [[EOCSomeClass alloc] init];
     [object doSomethingThatMayThrow];
}

@catch (...) {
 NSLog(@"Whoops, there was an error. Oh well...");
}

@interface EOCClassA : NSObject
@property (nonatomic, strong) EOCClassB *other;
@end


@interface EOCClassB : NSObject
@property (nonatomic, strong) EOCClassA *other;
@end

//EOCClassB.m
//第一种弱引用：unsafe_unretained
@property (nonatomic, unsafe_unretained) EOCClassA *other;


//第二种弱引用：weak
@property (nonatomic, weak) EOCClassA *other;

for (int i = 0; i < 100000; i++) {
      [self doSomethingWithInt:i];
}

NSArray *databaseRecords = /* ... */;
NSMutableArray *people = [NSMutableArray new];
for (NSDictionary *record in databaseRecords) {
     @autoreleasepool {
             EOCPerson *person = [[EOCPerson alloc] initWithRecord:record];
            [people addObject:person];
      }
}

int (^variableName)(BOOL flag, int value) =^(BOOL flag, int value){
     // Implementation
     return someInt;
}

EOCSomeBlock block = ^(BOOL flag, int value){
     // Implementation
};

- (void)startWithCompletionHandler: (void(^)(NSData *data, NSError *error))completion;

typedef void(^EOCCompletionHandler)(NSData *data, NSError *error);
- (void)startWithCompletionHandler:(EOCCompletionHandler)completion;”

- (void)fetchFooData {

     NSURL *url = [[NSURL alloc] initWithString:@"http://www.example.com/foo.dat"];
    _fooFetcher = [[EOCNetworkFetcher alloc] initWithURL:url];
    _fooFetcher.delegate = self;
    [_fooFetcher start];

}

- (void)fetchBarData {

     NSURL *url = [[NSURL alloc] initWithString: @"http://www.example.com/bar.dat"];
    _barFetcher = [[EOCNetworkFetcher alloc] initWithURL:url];
    _barFetcher.delegate = self;
    [_barFetcher start];

}

- (void)networkFetcher:(EOCNetworkFetcher*)networkFetcher didFinishWithData:(NSData*)data
{   //判断下载器类型
     if (networkFetcher == _fooFetcher) {
        _fetchedFooData = data;
        _fooFetcher = nil;

    } else if (networkFetcher == _barFetcher) {
        _fetchedBarData = data;
        _barFetcher = nil;
    }
}

- (void)fetchFooData {

     NSURL *url = [[NSURL alloc] initWithString:@"http://www.example.com/foo.dat"];
     EOCNetworkFetcher *fetcher =
     [[EOCNetworkFetcher alloc] initWithURL:url];
     [fetcher startWithCompletionHandler:^(NSData *data){
            _fetchedFooData = data;
   }];

}

- (void)fetchBarData {

     NSURL *url = [[NSURL alloc] initWithString: @"http://www.example.com/bar.dat"];
     EOCNetworkFetcher *fetcher =[[EOCNetworkFetcher alloc] initWithURL:url];
    [fetcher startWithCompletionHandler:^(NSData *data){
            _fetchedBarData = data;
    }];
} 

“#import <Foundation/Foundation.h>

@class EOCNetworkFetcher;
typedef void(^EOCNetworkFetcherCompletionHandler)(NSData *data);
typedef void(^EOCNetworkFetcherErrorHandler)(NSError *error);


@interface EOCNetworkFetcher : NSObject

- (id)initWithURL:(NSURL*)url;
- (void)startWithCompletionHandler: (EOCNetworkFetcherCompletionHandler)completion failureHandler: (EOCNetworkFetcherErrorHandler)failure;

@end



EOCNetworkFetcher *fetcher =[[EOCNetworkFetcher alloc] initWithURL:url];
[fetcher startWithCompletionHander:^(NSData *data){
     // Handle success
}

 failureHandler:^(NSError *error){
 // Handle failure
}];

“#import <Foundation/Foundation.h>


@class EOCNetworkFetcher;
typedef void(^EOCNetworkFetcherCompletionHandler)(NSData *data, NSError *error);

@interface EOCNetworkFetcher : NSObject

- (id)initWithURL:(NSURL*)url;
- (void)startWithCompletionHandler:

(EOCNetworkFetcherCompletionHandler)completion;

@end



EOCNetworkFetcher *fetcher =[[EOCNetworkFetcher alloc] initWithURL:url];

[fetcher startWithCompletionHander:

^(NSData *data, NSError *error){

if (error) {

     // Handle failure

} else {

     // Handle success

}
}];

@implementation EOCClass {

     EOCNetworkFetcher *_networkFetcher;
     NSData *_fetchedData;

}


- (void)downloadData {

     NSURL *url = [[NSURL alloc] initWithString:@"http://www.example.com/something.dat"];
    _networkFetcher =[[EOCNetworkFetcher alloc] initWithURL:url];

    [_networkFetcher startWithCompletionHandler:^(NSData *data){

             NSLog(@"Request URL %@ finished", _networkFetcher.url);
            _fetchedData = data;

    }];

}

- (void)downloadData {

     NSURL *url = [[NSURL alloc] initWithString:@"http://www.example.com/something.dat"];
    _networkFetcher =[[EOCNetworkFetcher alloc] initWithURL:url];
    [_networkFetcher startWithCompletionHandler:^(NSData *data){

             NSLog(@"Request URL %@ finished", _networkFetcher.url);
            _fetchedData = data;
            _networkFetcher = nil;

    }];

}

_syncQueue = dispatch_queue_create("com.effectiveobjectivec.syncQueue", NULL);

//读取字符串
- (NSString*)someString {

         __block NSString *localSomeString;
         dispatch_sync(_syncQueue, ^{
            localSomeString = _someString;
        });
         return localSomeString;

}

//设置字符串
- (void)setSomeString:(NSString*)someString {

     dispatch_sync(_syncQueue, ^{
        _someString = someString;
    });
}

_syncQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

//读取字符串
- (NSString*)someString {

     __block NSString *localSomeString;
     dispatch_sync(_syncQueue, ^{
        localSomeString = _someString;
    });
     return localSomeString;
}


//设置字符串
- (void)setSomeString:(NSString*)someString {

     dispatch_barrier_async(_syncQueue, ^{
        _someString = someString;
    });

}

// 使用 performSelector:withObject:afterDelay:
[self performSelector:@selector(doSomething) withObject:nil afterDelay:5.0];


// 使用 dispatch_after
dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5.0 * NSEC_PER_SEC));
dispatch_after(time, dispatch_get_main_queue(), ^(void){
    [self doSomething];
});

// 使用 performSelectorOnMainThread:withObject:waitUntilDone:
[self performSelectorOnMainThread:@selector(doSomething) withObject:nil waitUntilDone:NO];


// 使用 dispatch_async
// (or if waitUntilDone is YES, then dispatch_sync)
dispatch_async(dispatch_get_main_queue(), ^{
        [self doSomething];
});

//一个优先级低的并发队列
dispatch_queue_t lowPriorityQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0);

//一个优先级高的并发队列
dispatch_queue_t highPriorityQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);

//创建dispatch_group
dispatch_group_t dispatchGroup = dispatch_group_create();

//将优先级低的队列放入dispatch_group
for (id object in lowPriorityObjects) {
 dispatch_group_async(dispatchGroup,lowPriorityQueue,^{ [object performTask]; });
}

//将优先级高的队列放入dispatch_group
for (id object in highPriorityObjects) {
 dispatch_group_async(dispatchGroup,highPriorityQueue,^{ [object performTask]; });
}

//dispatch_group里的任务都结束后调用块中的代码
dispatch_queue_t notifyQueue = dispatch_get_main_queue();
dispatch_group_notify(dispatchGroup,notifyQueue,^{
     // Continue processing after completing tasks
});

+ (id)sharedInstance {

     static EOCClass *sharedInstance = nil;
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{
            sharedInstance = [[self alloc] init];
    });
     return sharedInstance;
}

NSArray *anNSArray = @[@1, @2, @3, @4, @5];
CFArrayRef aCFArray = (__bridge CFArrayRef)anNSArray;
NSLog(@"Size of array = %li", CFArrayGetCount(aCFArray));