一写妥、拷貝對(duì)象的基本概念
拷貝一個(gè)對(duì)象的副本鸳粉，開(kāi)辟一塊新的內(nèi)存來(lái)存儲(chǔ)副本對(duì)象
二捌蚊、淺拷貝和深拷貝
1集畅、淺拷貝
淺拷貝就是對(duì)對(duì)象內(nèi)存地址的拷貝，讓目標(biāo)指針和源指針指向同一片內(nèi)存空間缅糟。
淺拷貝只是對(duì)對(duì)象的簡(jiǎn)單拷貝挺智，讓幾個(gè)指針共用一片內(nèi)存，當(dāng)內(nèi)存銷(xiāo)毀的時(shí)候窗宦，指向這片內(nèi)存的幾個(gè)指針需要重新定義才可以使用赦颇，不然會(huì)成為野指針。
在iOS中赴涵，使用retain媒怯，是一種更加保險(xiǎn)的淺拷貝。它讓幾個(gè)指針共用同一塊內(nèi)存空間髓窜。 由于引用計(jì)數(shù)的存在扇苞，不會(huì)輕易的銷(xiāo)毀內(nèi)存，達(dá)到更加簡(jiǎn)單使用的目的寄纵。
2鳖敷、深拷貝
深拷貝是指拷貝對(duì)象的具體內(nèi)容，而內(nèi)存地址是自主分配的程拭，拷貝結(jié)束之后哄陶，兩個(gè)對(duì)象雖然存的值是相同的，但是內(nèi)存地址不一樣哺壶，兩個(gè)對(duì)象也互不影響屋吨，互不干涉蜒谤。
三、協(xié)議
如果一個(gè)對(duì)象想具備拷貝的功能至扰，必須實(shí)現(xiàn)協(xié)議鳍徽。
NSObject自帶的常用的對(duì)象有：NSNumber、NSString敢课、NSArray阶祭、NSDictionary、NSMutableString直秆、NSMutableArray濒募、NSMutableDictionary
iOS提供了copy和mutableCopy方法，顧名思義圾结，copy就是復(fù)制了一個(gè)imutable的對(duì)象瑰剃，而mutableCopy就是復(fù)制了一個(gè)mutable的對(duì)象。
當(dāng)然在iOS中并不是所有的對(duì)象都支持copy和mutableCopy筝野，遵守NSCopying 協(xié)議的類(lèi)可以發(fā)送copy消息晌姚，遵守NSMutableCopying 協(xié)議的類(lèi)才可以發(fā)送mutableCopy消息。假如發(fā)送了一個(gè)沒(méi)有遵守上述兩協(xié)議而發(fā)送copy或者mutableCopy歇竟，那么就會(huì)發(fā)生異常挥唠。但是默認(rèn)的iOS類(lèi)并沒(méi)有遵守這兩個(gè)協(xié)議。如果想自定義copy就必須遵守NSCopying焕议，并且實(shí)現(xiàn)copyWithZone:方法宝磨，如果想自定義mutableCopy就必須遵守NSMutableCopying，并且實(shí)現(xiàn)mutableCopyWithZone:方法盅安。
四唤锉、copy和retain的區(qū)別
copy是創(chuàng)建一個(gè)對(duì)象，retain是創(chuàng)建一個(gè)指針宽堆。
copy屬性表示兩個(gè)對(duì)象內(nèi)容相同腌紧，新的對(duì)象引用計(jì)數(shù)為1 茸习，與舊有對(duì)象的引用計(jì)數(shù)無(wú)關(guān)畜隶，舊有對(duì)象沒(méi)有變化。copy減少對(duì)象對(duì)上下文的依賴号胚。
retain屬性表示兩個(gè)對(duì)象地址相同（建立一個(gè)指針籽慢，指針拷貝），內(nèi)容當(dāng)然相同猫胁，這個(gè)對(duì)象的引用計(jì)數(shù)+1箱亿。
也就是說(shuō)，retain 是指針拷貝（淺拷貝）弃秆，copy 是對(duì)象拷貝（深拷貝）届惋。
五髓帽、探究
#define MyLog(Comment, Obj) NSLog(@"注釋:%@_指針地址:%p_對(duì)象地址:%p_對(duì)象:%@_引用計(jì)數(shù):%ld", Comment, &Obj, Obj, Obj, [Obj retainCount]);
1、系統(tǒng)的非容器類(lèi)對(duì)象
（NSString脑豹，NSNumber等一類(lèi)的對(duì)象）
1.1郑藏、不可變對(duì)象
NSString *string = @"Hello";
MyLog(@"String", string);
NSString *copyString = [string copy];
MyLog(@"CopyString", copyString);
NSString *mutableCopyString = [string mutableCopy];
MyLog(@"MutableCopyString", mutableCopyString);
string = @"World";
MyLog(@"String", string);
MyLog(@"CopyString", copyString);
MyLog(@"MutableCopyString", mutableCopyString);
2019-12-17 14:13:05.888336+0800 CopyTest[5239:233232] 注釋:String_指針地址:0x7ffeee082a38_對(duì)象地址:0x101b7c050_對(duì)象:Hello_引用計(jì)數(shù):-1
2019-12-17 14:13:07.112412+0800 CopyTest[5239:233232] 注釋:CopyString_指針地址:0x7ffeee082a30_對(duì)象地址:0x101b7c050_對(duì)象:Hello_引用計(jì)數(shù):-1
2019-12-17 14:13:10.228491+0800 CopyTest[5239:233232] 注釋:MutableCopyString_指針地址:0x7ffeee082a28_對(duì)象地址:0x600003558990_對(duì)象:Hello_引用計(jì)數(shù):1
2019-12-17 14:13:16.821985+0800 CopyTest[5239:233232] 注釋:String_指針地址:0x7ffeee082a38_對(duì)象地址:0x101b7c0f0_對(duì)象:World_引用計(jì)數(shù):-1
2019-12-17 14:13:25.889237+0800 CopyTest[5239:233232] 注釋:CopyString_指針地址:0x7ffeee082a30_對(duì)象地址:0x101b7c050_對(duì)象:Hello_引用計(jì)數(shù):-1
2019-12-17 14:13:58.920537+0800 CopyTest[5239:233232] 注釋:MutableCopyString_指針地址:0x7ffeee082a28_對(duì)象地址:0x600003558990_對(duì)象:Hello_引用計(jì)數(shù):1
查看Log可發(fā)現(xiàn)，string和copyString指向的是同一塊內(nèi)存區(qū)域瘩欺。而mutableCopyString則是我們所說(shuō)的真正意義上的拷貝必盖，系統(tǒng)為其分配了新內(nèi)存，引用計(jì)數(shù)為1俱饿，指針?biāo)赶虻淖址畠?nèi)容和string所指的一樣歌粥。
1.2、可變對(duì)象
NSMutableString *mutableString = [NSMutableString stringWithFormat:@"Hello"];
MyLog(@"MutableString", mutableString);
NSString *copyMutableString = [mutableString copy];
MyLog(@"CopyMutableString", copyMutableString);
NSString *mutableCopyMutableString = [mutableString mutableCopy];
MyLog(@"MutableCopyMutableString", mutableCopyMutableString);
mutableString = [NSMutableString stringWithFormat:@"World"];
MyLog(@"MutableString", mutableString);
MyLog(@"CopyMutableString", copyMutableString);
MyLog(@"MutableCopyMutableString", mutableCopyMutableString);
2019-12-17 14:22:47.659570+0800 CopyTest[5512:258797] 注釋:MutableString_指針地址:0x7ffee358ea38_對(duì)象地址:0x600002204c00_對(duì)象:Hello_引用計(jì)數(shù):1
2019-12-17 14:22:49.269361+0800 CopyTest[5512:258797] 注釋:CopyMutableString_指針地址:0x7ffee358ea30_對(duì)象地址:0x8d16218c3feb7c2b_對(duì)象:Hello_引用計(jì)數(shù):-1
2019-12-17 14:22:53.712337+0800 CopyTest[5512:258797] 注釋:MutableCopyMutableString_指針地址:0x7ffee358ea28_對(duì)象地址:0x600002254000_對(duì)象:Hello_引用計(jì)數(shù):1
2019-12-17 14:22:58.449147+0800 CopyTest[5512:258797] 注釋:MutableString_指針地址:0x7ffee358ea38_對(duì)象地址:0x600002204ab0_對(duì)象:World_引用計(jì)數(shù):1
2019-12-17 14:23:06.121620+0800 CopyTest[5512:258797] 注釋:CopyMutableString_指針地址:0x7ffee358ea30_對(duì)象地址:0x8d16218c3feb7c2b_對(duì)象:Hello_引用計(jì)數(shù):-1
2019-12-17 14:23:09.417593+0800 CopyTest[5512:258797] 注釋:MutableCopyMutableString_指針地址:0x7ffee358ea28_對(duì)象地址:0x600002254000_對(duì)象:Hello_引用計(jì)數(shù):1
copy產(chǎn)生的對(duì)象是不可變的拍埠，mutableCopy產(chǎn)生的對(duì)象是可變的
對(duì)于系統(tǒng)的非容器類(lèi)對(duì)象失驶，我們可以認(rèn)為，如果對(duì)一不可變對(duì)象拷貝械拍，copy是指針拷貝（淺拷貝）突勇，mutableCopy就是對(duì)象拷貝（深拷貝）。如果是對(duì)可變對(duì)象拷貝坷虑，都是深拷貝甲馋，但是copy返回的對(duì)象是不可變的。
2迄损、系統(tǒng)的容器類(lèi)對(duì)象
（NSArray定躏，NSDictionary等一類(lèi)的對(duì)象， 對(duì)于容器類(lèi)本身芹敌，上面討論的結(jié)論也是適用的痊远，需要探討的是拷貝后容器內(nèi)對(duì)象的變化。）
2.1氏捞、不可變對(duì)象
NSObject *object = [[NSObject alloc] init];
NSArray *array = @[object];
MyLog(@"Array", array);
NSArray *copyArray = [array copy];
MyLog(@"CopyArray", copyArray);
NSMutableArray *mutableCopyArray = [array mutableCopy];
MyLog(@"MutableCopyArray", mutableCopyArray);
array = @[object, object];
MyLog(@"Array", array);
MyLog(@"CopyArray", copyArray);
MyLog(@"MutableCopyArray", mutableCopyArray);
2019-12-17 14:48:05.654817+0800 CopyTest[6223:303565] 注釋:Array_指針地址:0x7ffeee88ca10_對(duì)象地址:0x600001384c60_對(duì)象:(
"<NSObject: 0x600001384c50>"
)_引用計(jì)數(shù):1
2019-12-17 14:48:05.655102+0800 CopyTest[6223:303565] 注釋:CopyArray_指針地址:0x7ffeee88ca08_對(duì)象地址:0x600001384c60_對(duì)象:(
"<NSObject: 0x600001384c50>"
)_引用計(jì)數(shù):2
2019-12-17 14:48:05.655236+0800 CopyTest[6223:303565] 注釋:MutableCopyArray_指針地址:0x7ffeee88ca00_對(duì)象地址:0x600001fc5b60_對(duì)象:(
"<NSObject: 0x600001384c50>"
)_引用計(jì)數(shù):1
2019-12-17 14:48:05.655349+0800 CopyTest[6223:303565] 注釋:Array_指針地址:0x7ffeee88ca10_對(duì)象地址:0x600001191dc0_對(duì)象:(
"<NSObject: 0x600001384c50>",
"<NSObject: 0x600001384c50>"
)_引用計(jì)數(shù):1
2019-12-17 14:48:05.655451+0800 CopyTest[6223:303565] 注釋:CopyArray_指針地址:0x7ffeee88ca08_對(duì)象地址:0x600001384c60_對(duì)象:(
"<NSObject: 0x600001384c50>"
)_引用計(jì)數(shù):2
2019-12-17 14:48:05.655525+0800 CopyTest[6223:303565] 注釋:MutableCopyArray_指針地址:0x7ffeee88ca00_對(duì)象地址:0x600001fc5b60_對(duì)象:(
"<NSObject: 0x600001384c50>"
)_引用計(jì)數(shù):1
copyArray是指針拷貝碧聪，而mutableCopyArray是對(duì)象拷貝，mutableCopyArray還可以改變內(nèi)部的元素：刪除或添加液茎。但是注意的是逞姿，容器內(nèi)的元素內(nèi)容都是指針拷貝。
2.2捆等、可變對(duì)象
NSObject *object = [[NSObject alloc] init];
NSMutableArray *mutableArray = [NSMutableArray arrayWithObject:object];
MyLog(@"MutableArray", mutableArray);
NSArray *copyMutableArray = [mutableArray copy];
MyLog(@"CopyMutableArray", copyMutableArray);
NSMutableArray *mutableCopyMutableArray = [mutableArray mutableCopy];
MyLog(@"MutableCopyMutableArray", mutableCopyMutableArray);
[mutableArray addObject:object];
MyLog(@"MutableArray", mutableArray);
MyLog(@"CopyMutableArray", copyMutableArray);
MyLog(@"MutableCopyArray", mutableCopyMutableArray);
2019-12-17 14:53:20.011397+0800 CopyTest[6368:322462] 注釋:MutableArray_指針地址:0x7ffeed6b5a30_對(duì)象地址:0x6000021f9f20_對(duì)象:(
"<NSObject: 0x600002da7700>"
)_引用計(jì)數(shù):1
2019-12-17 14:53:26.402298+0800 CopyTest[6368:322462] 注釋:CopyMutableArray_指針地址:0x7ffeed6b5a28_對(duì)象地址:0x600002da7710_對(duì)象:(
"<NSObject: 0x600002da7700>"
)_引用計(jì)數(shù):1
2019-12-17 14:53:35.683280+0800 CopyTest[6368:322462] 注釋:MutableCopyMutableArray_指針地址:0x7ffeed6b5a20_對(duì)象地址:0x6000021e61f0_對(duì)象:(
"<NSObject: 0x600002da7700>"
)_引用計(jì)數(shù):1
2019-12-17 14:53:40.723298+0800 CopyTest[6368:322462] 注釋:MutableArray_指針地址:0x7ffeed6b5a30_對(duì)象地址:0x6000021f9f20_對(duì)象:(
"<NSObject: 0x600002da7700>",
"<NSObject: 0x600002da7700>"
)_引用計(jì)數(shù):1
2019-12-17 14:53:47.418461+0800 CopyTest[6368:322462] 注釋:CopyMutableArray_指針地址:0x7ffeed6b5a28_對(duì)象地址:0x600002da7710_對(duì)象:(
"<NSObject: 0x600002da7700>"
)_引用計(jì)數(shù):1
2019-12-17 14:53:50.173948+0800 CopyTest[6368:322462] 注釋:MutableCopyArray_指針地址:0x7ffeed6b5a20_對(duì)象地址:0x6000021e61f0_對(duì)象:(
"<NSObject: 0x600002da7700>"
)_引用計(jì)數(shù):1
由此可見(jiàn)滞造，對(duì)于容器而言，其元素對(duì)象始終是指針拷貝栋烤。如果需要元素對(duì)象也是對(duì)象拷貝谒养，就需要自己實(shí)現(xiàn)深拷貝。
