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深浅拷贝的区别:
深拷贝 拷贝 内容
浅拷贝 拷贝 地址
注:当对象str1在常量区时
①对不可变字符串NSString对象进行copy
NSString *str1 = @"Hello"; //str1 -- 常量区 NSLog(@"%p", str1);//0x100002048 //copy NSString *str2 = [str1 copy];//0x100002048 str2 -- 常量区 NSLog(@"%p", str2);//str2 与 str1都指向常量区,地址相同,引用计数为无穷大 NSLog(@"str2 retaincount = %lu", [str2 retainCount]);<span style="font-size:18px;">//18446744073709551615</span>②对不可变字符串NSString对象进行mutableCopy
//mutableCopy,深拷贝,拷贝内容,而且拷贝出来的是一个可变的对象 NSMutableString *str3 = [str1 mutableCopy]; NSLog(@"str3 retaincount = %lu", [str3 retainCount]);//1 [str3 appendString:@"world"];//对拷贝出来的对象进行操作 NSLog(@"str3 = %@", str3);注:当对象str1在堆区时
NSString *str1 = [NSString stringWithFormat:@"Frank"]; NSLog(@"str1 = %p, retaincount = %lu", str1, [str1 retainCount]);//1①对不可变字符串NSString对象进行copy
//copy, 浅拷贝, 拷贝 地址, 并且将原有对象的引用计数加1. NSString *str2 = [str1 copy];// str2与str1指向同一块堆区空间 NSLog(@"str2 = %p, retaincount = %lu", str2, [str2 retainCount]);//2②对不可变字符串NSString对象进行mutableCopy
//mutableCopy,深拷贝,拷贝内容,堆区开辟新的空间,并且拷贝出来的对象是可变的. NSMutableString *str3 = [str1 mutableCopy];//str3与str1指向不同的对象 [str3 appendString:@"lanou"]; NSLog(@"str3 = %p, retaincount = %lu", str3, [str3 retainCount]);//1可变字符串(NSMutableString)
//原有对象str1在堆区 NSMutableString *str1 = [[NSMutableString alloc] initWithFormat:@"Frank"]; NSLog(@"str1 = %p", str1);//0x10010b800 //copy 堆区中开辟新的空间,拷贝内容到新的空间上,但是拷贝出来的是不可变字符串对象. NSString *str2 = [str1 copy]; NSLog(@"str2 = %p, retaincount = %lu", str2, [str2 retainCount]);//1②对一个可变字符串NSMutableString对象mutableCopy
//mutableCopy 堆区中开辟新的空间,拷贝内容到新的空间上,但是拷贝出来的是可变字符串对象. NSMutableString *str3 = [str1 mutableCopy]; [str3 appendString:@"lanou"]; NSLog(@"str3 = %p, retaincount = %lu", str3, [str3 retainCount]);总结:
/** * 总结:拷贝是分为可变对象与不可变对象. 浅拷贝 --- 只拷贝对象地址,不会拷贝内容,不会开辟新的空间. 深拷贝 --- 拷贝内容,堆区开辟新的空间. 不可变对象: 1.copy 相当于retin, 原有对象引用计数加1,拷贝地址. 2.mutableCopy 复制出新的对象,并且对象是可变的,开呗内容. 可变对象: 1.copy 复制出新的对象,但是对象是不可变的,拷贝内容. 2.mutableCopy 复制出新的对象,但是对象是可变的,拷贝内容. */③.对一个自定义对象Copy和mutableCopy,需要服从<NSCopying, NSMutableCopying>协议,例如:
1.创建Person.h
@interface Person : NSObject <NSCopying, NSMutableCopying> @property (nonatomic, copy) NSString *name; //姓名 @property (nonatomic, copy) NSString *gender; //性别 @property (nonatomic) NSInteger age;//年龄 @end2.Person.m文件服从协议
@implementation Person - (id)copyWithZone:(NSZone *)zone { Person *newPerson = [[[self class] allocWithZone:zone] init]; newPerson.name = [self.name copy]; newPerson.gender = [self.gender copy]; newPerson.age = self.age; return newPerson; } - (id)mutableCopyWithZone:(NSZone *)zone { Person *newPerson = [[[self class] allocWithZone:zone] init]; newPerson.name = [self.name mutableCopy]; newPerson.gender = [self.gender mutableCopy]; newPerson.age = self.age; return newPerson; } - (void)dealloc { self.name = nil; self.gender = nil; [super dealloc]; } @end实现,对深浅拷贝分析
//Person copy 与 mutableCopy NSString *name = [NSString stringWithFormat:@"Wang"]; NSString *gender = [NSString stringWithFormat:@"Man"]; Person *per = [[Person alloc] init]; per.name = name; per.gender = gender; NSLog(@"per = %p", per);//0x10010b980 //per name = 0x100100560, gender = 0x100104ac0(拷贝前地址) NSLog(@"per name = %p, gender = %p", per.name, per.gender); Person *copyPerson = [per copy]; //copyPerson = 0x100500a90, retaincount = 1(拷贝后地址) NSLog(@"copyPerson = %p, retaincount = %lu", copyPerson, [copyPerson retainCount]); //(拷贝后内容地址不变,把地址拷贝过去) //copyPerson name = 0x100100560, gender = 0x100104ac0 NSLog(@"copyPerson name = %p, gender = %p", copyPerson.name, copyPerson.gender); Person *mutaCopyPerson = [per mutableCopy]; //copymutaCopyPersonPerson = 0x100401d50, retaincount = 1 NSLog(@"copymutaCopyPersonPerson = %p, retaincount = %lu", mutaCopyPerson, [mutaCopyPerson retainCount]); //(mutableCopy)地址不同,即拷贝是内容 //mutaCopyPerson name = 0x100401450, gender = 0x1004014e0 NSLog(@"mutaCopyPerson name = %p, gender = %p", mutaCopyPerson.name, mutaCopyPerson.gender);
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原文地址:http://blog.csdn.net/zfx5130/article/details/42970867