探讨NSString和NSMutableString的内存问题以及copy和MutableCopy两个方法

 1 //main.m     
 2 #import <Foundation/Foundation.h>
 3 
 4 int main(int argc, const char * argv[]) {
 5     @autoreleasepool {
 6 
 7         NSMutableString *str1 = [[NSMutableString alloc]initWithCapacity:0];
 8         NSMutableString *str2;
 9         NSMutableString *str3;
10         NSMutableString *str4;
11         NSMutableString *str5;
12         NSMutableString *str6;
13         NSMutableString *str7;
14         
15         
16         NSLog(@"@\"a\" address = %p", @"aaa");
17         NSLog(@"change before:");
18         str1 = [NSMutableString stringWithString:@"aaa"];
19         
20         str2 = str1;
21         str3 = [NSMutableString stringWithString:str1];
22         str4 = [[NSMutableString alloc]initWithString:str1];
23         str5 = [[NSMutableString alloc]initWithCapacity:0];
24         [str5 setString:str1];
25         str6 = [str1 copy];
26         str7 = [str1 mutableCopy];
27         
28         NSLog(@"str1 = %@", str1);            //输出str1内容
29         NSLog(@"str1 address = %p", str1);    //输出str1内容所在的地址
30         NSLog(@"str2 = %@", str2);            //输出str2内容
31         NSLog(@"str2 address = %p", str2);    //输出str2内容所在的地址
32         NSLog(@"str3 = %@", str3);            //输出str3内容
33         NSLog(@"str3 address = %p", str3);       //输出str3内容所在的地址
34         NSLog(@"str4 = %@", str4);            //输出str4内容
35         NSLog(@"str4 address = %p", str4);   //输出str4内容所在的地址
36         NSLog(@"str5 = %@", str5);          //输出str5内容
37         NSLog(@"str5 address = %p", str5);   //输出str5内容所在的地址
38         NSLog(@"str6 = %@", str6);          //输出str6内容
39         NSLog(@"str6 address = %p", str6);   //输出str6内容所在的地址
40         NSLog(@"str7 = %@", str7);           //输出str7内容
41         NSLog(@"str7 address = %p", str7);    //输出str7内容所在的地址
42        
43         NSLog(@" ");
44         NSLog(@"@\"bbb\" address = %p", @"bbb");
45         NSLog(@"change after:");
46         [str1 setString:@"bbb"];
47         NSLog(@"str1 = %@", str1);            //输出修改后str1内容
48         NSLog(@"str1 address = %p", str1);    //输出修改后str1内容所在地址
49         NSLog(@"str2 = %@", str2);             //输出修改后str2内容
50         NSLog(@"str2 address = %p", str2);     //输出修改后str2内容所在地址
51         NSLog(@"str3 = %@", str3);            //输出修改后str3内容
52         NSLog(@"str3 address = %p", str3);     //输出修改后str3内容所在地址
53         NSLog(@"str4 = %@", str4);           //输出修改后str4内容
54         NSLog(@"str4 address = %p", str4);     //输出修改后str4内容所在地址
55         NSLog(@"str5 = %@", str5);           //输出修改后str5内容
56         NSLog(@"str5 address = %p", str5);   //输出修改后str5内容所在地址
57         NSLog(@"str6 = %@", str6);             //输出修改后str6内容
58         NSLog(@"str6 address = %p", str6);     //输出修改后str6内容所在地址
59         NSLog(@"str7 = %@", str7);             //输出修改后str7内容
60         NSLog(@"str7 address = %p", str7);     //输出修改后str7内容所在地址
61         
62     }
63     return 0;
64 }     

 1 //main.m
 2 
 3 #import <Foundation/Foundation.h>
 4 
 5 int main(int argc, const char * argv[]) {
 6     @autoreleasepool {
 7 
 8         NSString *str1 = @"a";
 9         NSMutableString *str2;
10         NSMutableString *str3;
11         
12         NSMutableString *str4 = [NSMutableString stringWithString:@"a"];
13         NSString *str5;
14         NSString *str6;
15  
16         //一个不可变字符串str1使用copy和MutableCopy创建两个新副本给2个可变字符串str2和str3
17         str2 = [str1 copy];
18         str3 = [str1 mutableCopy];
19         
20         //一个可变字符串str4使用copy和MutableCopy创建两个新副本给2个不可变字符串str5和str6
21         str5 = [str4 copy];
22         str6 = [str4 mutableCopy];
23         
24         NSLog(@"str1 address = %p", str1);
25         NSLog(@"str2 address = %p", str2);
26         NSLog(@"str3 address = %p", str3);
27         NSLog(@"str4 address = %p", str4);
28         NSLog(@"str5 address = %p", str5);
29         NSLog(@"str6 address = %p", str6);
30     
31     }
32     return 0;
33 }

1 //运行结果：
2 
3 2016-06-05 16:57:01.697 copyTest[2175:117425] str1 address = 0x100001050
4 2016-06-05 16:57:01.698 copyTest[2175:117425] str2 address = 0x100001050
5 2016-06-05 16:57:01.698 copyTest[2175:117425] str3 address = 0x100203980
6 2016-06-05 16:57:01.698 copyTest[2175:117425] str4 address = 0x1002037b0
7 2016-06-05 16:57:01.698 copyTest[2175:117425] str5 address = 0x6115
8 2016-06-05 16:57:01.698 copyTest[2175:117425] str6 address = 0x100203a70
9 Program ended with exit code: 0