objective-c中的深、浅拷贝

2019-11-14 19:20:09

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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;}

源代码

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") 0x1001145702015-04-01 20:46:23.133 04-01-person[2204:165655] array2:(    "two day") 0x1001147002015-04-01 20:46:23.133 04-01-person[2204:165655] array3:(    "two day") 0x1001147002015-04-01 20:46:23.133 04-01-person[2204:165655] array4:(    "two day") 0x1001147002015-04-01 20:46:23.133 04-01-person[2204:165655] array5:(    "two day") 0x1001145702015-04-01 20:46:23.133 04-01-person[2204:165655] array6:(    "two day") 0x1001150d02015-04-01 20:46:23.134 04-01-person[2204:165655] array7:(    "two day") 0x100115b002015-04-01 20:46:23.134 04-01-person[2204:165655] -------------PRogram ended with exit code: 0

运行结果

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;}

源代码

2015-04-01 21:00:28.218 04-01-person[2252:170414] array01: (    zhang,    wang,    li)  0x100106c802015-04-01 21:00:28.220 04-01-person[2252:170414] array02: (    zhang,    wang,    li)  0x1001076d0Program ended with exit code: 0

运行结果

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;}

源代码

2015-04-01 21:03:45.349 04-01-person[2263:171615] array1: (    zhang,    wang,    li)  0x1001129002015-04-01 21:03:45.350 04-01-person[2263:171615] array2: (    zhang,    wang,    li)  0x1001133b0

运行结果

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;}

源代码

2015-04-01 20:57:41.732 04-01-person[2243:169571] array1: (    zhang,    wang,    li)  0x1001145702015-04-01 20:57:41.734 04-01-person[2243:169571] array2: (    zhang,    wang,    li)  0x100115020Program ended with exit code: 0

运行结果

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;}

源代码

2015-04-01 20:53:07.398 04-01-person[2217:167996] array1: (    one,    two,    three)  0x1006069a02015-04-01 20:53:07.399 04-01-person[2217:167996] array2: (    one,    two,    three)  0x1006069a0Program ended with exit code: 0