NSMutableString * city = [NSMutableString stringWithString:@"北京"];
//复制可变副本
NSMutableString * cityCopy = [city mutableCopy];
//修改副本
[cityCopy replaceCharactersInRange:NSMakeRange(0, 2) withString:@"临沧"];
//输出看到原字符串没有改变 当前的改变
NSLog(@"原来的city是%@，现在的cityCopy是%@",city,cityCopy);
NSString * str =@"测试的字符串";
NSMutableString * strCopy = [str mutableCopy];
//增加字符串
[strCopy appendString:@"再加一段字符串"];
NSLog(@"strCopy是是%@",strCopy);
//为可变字符串返回一个不可变副本
NSMutableString * cityCopy2 = [city copy];
//由于city是不可变的下面的代码是错误的
[cityCopy2 appendString:@"这样是错的"];报错信息3.对象拷贝
对于自定义的对象我们需要实现NSCopying和NSMutableCopying@interface Person : NSObject @property(nonatomic,strong)NSMutableString *name; @property(nonatomic,assign)int age; @end
#import "Person.h"
@interface Person()<NSCopying>
@end
@implementation Person
- (id)copyWithZone:(NSZone *)zone{
Person * person = [[[self class] allocWithZone:zone] init];
person.name = self.name;
person.age = self.age;
return person;
}
@end#import <Foundation/Foundation.h>
#import "Person.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person * person = [Person new];
person.name = [NSMutableString stringWithString:@"小明"];
person.age = 20;
Person * personCopy = [person copy];//复制副本
personCopy.name = [NSMutableString stringWithString:@"小强"];
personCopy.age =23;
NSLog(@"person的名字是%@",person.name);
NSLog(@"person的n年龄是%d",person.age);
NSLog(@"personCopy的名字是%@",personCopy.name);
NSLog(@"personCopy的年龄是%d",personCopy.age);
// 2015-05-05 17:38:43.980 copyDemo[531:303] person的名字是小明
// 2015-05-05 17:38:43.981 copyDemo[531:303] person的n年龄是20
// 2015-05-05 17:38:43.981 copyDemo[531:303] personCopy的名字是小强
// 2015-05-05 17:38:43.982 copyDemo[531:303] personCopy的年龄是23
}
return 0;
}
4.浅拷贝
其他不变修改main函数 Person * person = [Person new];
person.name = [NSMutableString stringWithString:@"小明"];
person.age = 20;
Person * personCopy = [person copy];//复制副本
[personCopy.name replaceCharactersInRange:NSMakeRange(0,2) withString:@"变了嘛"];
personCopy.age =23;
NSLog(@"person的名字是%@",person.name);
NSLog(@"person的n年龄是%d",person.age);
NSLog(@"personCopy的名字是%@",personCopy.name);
NSLog(@"personCopy的年龄是%d",personCopy.age);打印出来的是2015-05-05 17:54:05.350 copyDemo[563:303] personCopy的年龄是23
一开始我也很迷惑。差距只有一句代码而已。不过还是有差别的。 person.name = self.name;
person.age = self.age; name是一个指针变量，存放的只是字符串地而已。所以说修改了拷贝的name，原来的name也会发生改变，使用personCopy.name = [NSMutableString stringWithString:@"小强"];这句代码的话其实是直接重新赋值，指向了另外一个字符串指针，所以拷贝的对象修改了。原来的并没有改变。但是并不代表拷贝的时候不指向一个字符串。只是后来被修改了。5.深拷贝
将copyWithZone方法里面的修改
person.name = [self.name mutableCopy];
person.age = self.age;这样就实现了深复制。6.setetr方法的复制
修改如下代码@property(nonatomic,copy)NSMutableString *name;修改main
Person * person = [Person new];
person.name = [NSMutableString stringWithString:@"小明"];
//下面这行代码会报错的。
[person.name appendString:@"会报错了"];name的属性使用了copy指示符的话其实相当于setNmame方法里面- (void)setName(NSString *)name{
name ＝ [name copy];
}是对参数的一个不可变拷贝原文：http://blog.csdn.net/zhouzhoujianquan/article/details/45506187