objective-c copy mutableCopy 拷貝對象

原來不是所有的對象都支援 copy

隻有遵守NSCopying 協定的類才可以發送copy消息

隻有遵守NSMutableCopying 協定的類才可以發送mutableCopy消息

假如發送了一個沒有遵守上訴兩協定而發送 copy或者 mutableCopy,那麼就會發生異常

預設 nsobject沒有遵守這兩個協定

但是 copy和mutableCopy這兩個方法是nsobject定義的

如果想自定義一下copy 那麼就必須遵守NSCopying,并且實作 copyWithZone: 方法

如果想自定義一下mutableCopy 那麼就必須遵守NSMutableCopying,并且實作 mutableCopyWithZone: 方法

看了一下幾個遵守 NSCopying協定的基本上是一些基礎核心類

比如 NSString NSNumber

copy以後,就是傳回一個新的類,你要負責釋放掉,原先被拷貝的retaincount沒有+1 是以,不需要負責釋放

copy和mutableCopy 就是copy傳回後的是不能修改的對象, mutableCopy傳回後是可以修改的對象

下面是實作一個copyWithZone的例子

@interface BankAccount: NSObject <NSCopying>

{

double accountBalance;

long accountNumber;

}

-(void) setAccount: (long) y andBalance: (double) x;

-(double) getAccountBalance;

-(long) getAccountNumber;

-(void) setAccountBalance: (double) x;

-(void) setAccountNumber: (long) y;

-(void) displayAccountInfo;

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

@end

-(id) copyWithZone: (NSZone *) zone

{

BankAccount *accountCopy = [[BankAccount allocWithZone: zone] init];

[accountCopy setAccount: accountNumber andBalance: accountBalance];

return accountCopy;

}

深度拷貝和淺拷貝

上面的方法是淺拷貝,意思就是,隻是重新配置設定了BankAccount類的記憶體,并沒有對BankAccount的屬性重新配置設定記憶體

兩個BankAccount的屬性都是指向同一個地方的. 修改了其中一個BankAccount屬性,那麼另外一個BankAccount屬性

也會一起發生變化 

深度拷貝

深度拷貝這裡用到一個存檔功能,先把原先的存檔(其實就是序列化對象,然後存到一個檔案,等下可以反序列化出來指派給另外一個對象),然後存到另外的而一個對象中

NSKeyedArchiver 序列化類

NSKeyedUnarchiver 反序列化類

NSArray *myArray1;

NSArray *myArray2;

NSMutableString *tmpStr;

NSMutableString *string1;

NSMutableString *string2;

NSMutableString *string3;

NSData *buffer;

string1 = [NSMutableString stringWithString: @"Red"];

string2 = [NSMutableString stringWithString: @"Green"];

string3 = [NSMutableString stringWithString: @"Blue"];

myArray1 = [NSMutableArray arrayWithObjects: string1, string2, string3, nil];

buffer = [NSKeyedArchiver archivedDataWithRootObject: myArray1];

myArray2 = [NSKeyedUnarchiver unarchiveObjectWithData: buffer];

tmpStr = [myArray1 objectAtIndex: 0];

[tmpStr setString: @"Yellow"];

NSLog (@"First element of myArray1 = %@", [myArray1 objectAtIndex: 0]);

NSLog (@"First element of myArray2 = %@", [myArray2 objectAtIndex: 0]);

cocoa的屬性也有3種

protected - Access is allowed only by methods of the class and any subclasses. 預設是這個

private - Access is restricted to methods of the class. Access is not available to subclasses. 

public - Direct access available to methods of the class, subclasses and code in other module files and classes.

public的變量可以用 -> 操作符通路

參考位址:http://www.techotopia.com/index.php/Copying_Objects_in_Objective-C

http://wenku.baidu.com/view/12d6592fb4daa58da0114af0.html

http://www.techotopia.com/index.php/Objective-C_-_Data_Encapsulation,_Synthesized_Accessors_and_Dot_Notation

關于通路器的詳細文檔

http://cocoacast.com/?q=node/103