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浅复制：只复制指向对象的指针，而不复制引用对象本身。计数器+1 ,就像比如retain
深层复制：复制引用对象本身。计数器不变，产生新对象
retain：始终是浅复制。引用计数每次加一。返回对象是否可变与被复制的对象保持一致。
copy：对于可变对象为深复制，引用计数不改变;对于不可变对象是浅复制，引用计数每次加一。始终返回一个不可变对象。
mutableCopy：始终是深复制，引用计数不改变。始终返回一个可变对象。
#import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { NSMutableArray *array1=[NSMutableArray arrayWithObjects:@"two day", nil]; NSMutableArray *array2=[array1 copy]; NSArray *array3=[array2 copy]; NSArray *array4=[array2 retain]; NSMutableArray *array5=[array1 retain]; NSMutableArray *array6=[array1 mutableCopy]; NSArray *array7=[array2 mutableCopy]; NSLog(@"-------------"); NSLog(@"array1:%@ %p",array1, array1); NSLog(@"array2:%@ %p",array2, array2); NSLog(@"array3:%@ %p",array3, array3); NSLog(@"array4:%@ %p",array4, array4); NSLog(@"array5:%@ %p",array5, array5); NSLog(@"array6:%@ %p",array6, array6); NSLog(@"array7:%@ %p",array7, array7); NSLog(@"-------------"); return 0; }
2015-04-01 20:46:23.131 04-01-person[2204:165655] ------------- 2015-04-01 20:46:23.132 04-01-person[2204:165655] array1:( "two day" ) 0x100114570 2015-04-01 20:46:23.133 04-01-person[2204:165655] array2:( "two day" ) 0x100114700 2015-04-01 20:46:23.133 04-01-person[2204:165655] array3:( "two day" ) 0x100114700 2015-04-01 20:46:23.133 04-01-person[2204:165655] array4:( "two day" ) 0x100114700 2015-04-01 20:46:23.133 04-01-person[2204:165655] array5:( "two day" ) 0x100114570 2015-04-01 20:46:23.133 04-01-person[2204:165655] array6:( "two day" ) 0x1001150d0 2015-04-01 20:46:23.134 04-01-person[2204:165655] array7:( "two day" ) 0x100115b00 2015-04-01 20:46:23.134 04-01-person[2204:165655] ------------- Program ended with exit code: 0
数组类型转换：
1、不可变对象→可变对象的转换：
#import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { NSArray *array01=[NSArray arrayWithObjects:@"zhang",@"wang",@"li", nil]; NSMutableArray *array02=[array01 mutableCopy]; //mutableCopy始终返回一个可变对象 NSLog(@"array01: %@ %p",array01,array01); NSLog(@"array02: %@ %p",array02,array02); return 0; }
2015-04-01 21:00:28.218 04-01-person[2252:170414] array01: ( zhang, wang, li ) 0x100106c80 2015-04-01 21:00:28.220 04-01-person[2252:170414] array02: ( zhang, wang, li ) 0x1001076d0 Program ended with exit code: 0
2、可变对象→不可变对象的转换：
#import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { NSMutableArray *array1 = [NSMutableArray arrayWithObjects:@"zhang",@"wang",@"li", nil]; NSArray *array2=[array1 copy];//copy对于可变对象为深复制，引用计数不改变;对于不可变对象是浅复制，引用计数每次加一。始终返回一个不可变对象 NSLog(@"array1: %@ %p",array1,array1); NSLog(@"array2: %@ %p",array2,array2); return 0; }
2015-04-01 21:03:45.349 04-01-person[2263:171615] array1: ( zhang, wang, li ) 0x100112900 2015-04-01 21:03:45.350 04-01-person[2263:171615] array2: ( zhang, wang, li ) 0x1001133b0
3、可变对象→可变对象的转换（不同指针变量指向不同的内存地址）：
#import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { NSMutableArray *array1= [NSMutableArray arrayWithObjects:@"zhang",@"wang",@"li", nil]; NSMutableArray *array2=[array1 mutableCopy]; NSLog(@"array1: %@ %p",array1,array1); NSLog(@"array2: %@ %p",array2,array2); return 0; }
2015-04-01 20:57:41.732 04-01-person[2243:169571] array1: ( zhang, wang, li ) 0x100114570 2015-04-01 20:57:41.734 04-01-person[2243:169571] array2: ( zhang, wang, li ) 0x100115020 Program ended with exit code: 0
4、同类型对象之间的指针复制（不同指针变量指向同一块内存地址）：
#import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { NSArray *array1=[NSArray arrayWithObjects:@"one",@"two",@"three", nil]; NSArray *array2=[array1 copy]; NSLog(@"array1: %@ %p",array1,array1); NSLog(@"array2: %@ %p",array2,array2); return 0; }
2015-04-01 20:53:07.398 04-01-person[2217:167996] array1: ( one, two, three ) 0x1006069a0 2015-04-01 20:53:07.399 04-01-person[2217:167996] array2: ( one, two, three ) 0x1006069a0 Program ended with exit code: 0
当多个指针同时指向同一块内存区域，那么这些个指针同时拥有对该内存区的所有权。所有权的瓜分过程，这时候就要用到浅拷贝了。
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原文地址：http://www.cnblogs.com/hecheng0314/p/4385346.html
