关于深拷贝、浅拷贝，请看上篇iOS – 深拷贝、浅拷贝探索验证

由上篇我们知道:

copy： 对NSArray是浅拷贝，NSMutableArray是深拷贝

mutableCopy： 始终是深拷贝

无论深浅拷贝，集合对象内元素都是浅拷贝

本篇主要探索

实现NSArray内元素的拷贝

通过本文你将知道

深拷贝NSArray

深拷贝NSArray内元素Person

深拷贝NSArray内元素Person的属性nickname

本文代码较多，建议一步步耐心跟着代码排查，会有不少收货

探索过程

1. 系统Api

我们发现系统系统了方法- (instancetype)initWithArray:(NSArray<ObjectType> *)array copyItems:(BOOL)flag
其中copyItems:(BOOL)flag表示是否拷贝元素，我们先代码测试一下

    NSString *str1 = @"hello world";
    NSMutableString *str2 = [NSMutableString stringWithString:@"hello world"];
    NSArray *array1 = [NSArray arrayWithObjects: str1, str2, nil];
    NSMutableArray *array2 = [[NSMutableArray alloc] initWithArray:array1 copyItems:true];

    NSLog(@"\n array1 = %p class = %@ \n", array1, [array1 class]);
    NSLog(@"\n array2 = %p class = %@ \n", array2, [array2 class]);

    NSLog(@"\n\n======== 元素是String ======== ");
    NSLog(@"\n obj0 = %p class = %@ \n", array1[0], [array1[0] class]);
    NSLog(@"\n obj0 = %p class = %@ \n", array2[0], [array2[0] class]);

    NSLog(@"\n\n======== 元素是mutableString ========");
    NSLog(@"\n obj0 = %p class = %@ \n", array1[1], [array1[1] class]);
    NSLog(@"\n obj0 = %p class = %@ \n", array2[1], [array2[1] class]);
复制代码

查看输出(为了下文对比，我对输出做了line标记)

2021-05-09 10:59:16.343163+0800 AlgorithmDemo[9904:51756] 
 array1 = 0x100607650 class = __NSArrayI  (line1)
 array2 = 0x1006074a0 class = __NSArrayM (line2)

======== 元素是String ======== 
 obj0 = 0x100008220 class = __NSCFConstantString (line3)
 obj0 = 0x100008220 class = __NSCFConstantString (line4)

======== 元素是mutableString ========
 obj0 = 0x100606330 class = __NSCFString (line5)
 obj0 = 0x100605430 class = __NSCFString (line6)
复制代码

根据输出我们对得出系统initWithArray : copyItems :方法如下结论

~~该方法对NSArray对象是深拷贝~~ (严格意义来说此处不能称为拷贝，是生成新对象) （line1 line2）
当数组内元素为不可变对象时，该方法对元素执行浅拷贝(line3 line4)
当数组内元素为可变对象时，该方法对元素执行深拷贝(line4 line5)

由此我们知道，当我们想深拷贝NSArray及其内部的元素时，用系统方法- (instancetype)initWithArray:(NSArray<ObjectType> *)array copyItems:(BOOL)flag是不行的

2. 归档

如果我们对Array执行归档再解档，结果会是什么样的呢，我们代码测试一下

    NSString *str1 = @"hello world";
    NSMutableString *str2 = [NSMutableString stringWithString:@"hello world"];
    NSArray *array1 = [NSArray arrayWithObjects: str1, str2, nil];
    NSMutableArray *array2 = [[NSMutableArray alloc] initWithArray:array1 copyItems:true];
    
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array1];
    NSMutableArray *array3 = [NSKeyedUnarchiver unarchiveObjectWithData:data];
    
    NSLog(@"\n array1 = %p class = %@ \n", array1, [array1 class]);
    NSLog(@"\n array2 = %p class = %@ \n", array2, [array2 class]);
    NSLog(@"\n array3 = %p class = %@ \n", array3, [array3 class]);
    
    NSLog(@"\n\n======== 元素是String ======== ");
    NSLog(@"\n obj0 = %p class = %@ \n", array1[0], [array1[0] class]);
    NSLog(@"\n obj0 = %p class = %@ \n", array2[0], [array2[0] class]);
    NSLog(@"\n obj0 = %p class = %@ \n", array3[0], [array3[0] class]);
    
    NSLog(@"\n\n======== 元素是mutableString ========");
    NSLog(@"\n obj0 = %p class = %@ \n", array1[1], [array1[1] class]);
    NSLog(@"\n obj0 = %p class = %@ \n", array2[1], [array2[1] class]);
    NSLog(@"\n obj0 = %p class = %@ \n", array3[1], [array3[1] class]);
复制代码

查看输出

2021-05-09 11:14:50.710409+0800 AlgorithmDemo[12261:67019] 
 array1 = 0x1006b9e40 class = __NSArrayI  (line1)
 array2 = 0x1006ba180 class = __NSArrayM  (line1)
 array3 = 0x1006b7410 class = __NSArrayI  (line1)

======== 元素是String ======== 
 obj0 = 0x100008220 class = __NSCFConstantString  (line1)
 obj0 = 0x100008220 class = __NSCFConstantString  (line1)
 obj0 = 0x1006b6d20 class = __NSCFString  (line1)

======== 元素是mutableString ========
 obj0 = 0x1006b9cb0 class = __NSCFString  (line1)
 obj0 = 0x1006ba0e0 class = __NSCFString  (line1)
 obj0 = 0x1006b70e0 class = __NSCFString  (line1)
复制代码

根据输出，我们很明显得出如下结论

对Array归档并解档后，会生成新的Array对象
Array对象内的不可变元素进行了深拷贝
Array对象内的可变元素进行了深拷贝

由此，我们得出对如下总结

只深拷贝NSArray对象，我们用mutableCopy就可以
只深拷贝NSMutableArray对象，我们用Copy或mutableCopy都可以
深拷贝Array对象及内部元素，我们可以通过归档的方法解决

3. 如果Array对象内元素是自定义对象呢

我们写一个person类测试一下

//
//  Person.h
//  AlgorithmDemo
//
//  Created by Ternence on 2021/5/9.
//

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property (nonatomic, copy) NSString *nickname;

@end
复制代码

测试代码如下

    Person *person = [[Person alloc] init];
    person.nickname = @"码代码的小马";
    
    NSMutableArray *array1 = [NSMutableArray arrayWithObjects:person, nil];
    
    NSArray *array2 = [array1 copy];
    NSMutableArray *array3 = [array1 mutableCopy];
    
    NSLog(@"\n array1 = %p class = %@", array1, [array1 class]);
    NSLog(@"\n array2 = %p class = %@", array2, [array2 class]);
    NSLog(@"\n array3 = %p class = %@", array3, [array3 class]);
    
    NSLog(@"\n\n======== 数组内元素 ======== ");
    NSLog(@"\n array1[0] = %p class = %@", array1[0], [array1[0] class]);
    NSLog(@"\n array2[0] = %p class = %@", array2[0], [array2[0] class]);
    NSLog(@"\n array3[0] = %p class = %@", array3[0], [array3[0] class]);
复制代码

查看输出

2021-05-09 11:33:47.241685+0800 AlgorithmDemo[17319:89117] 
 array1 = 0x102a04450 class = __NSArrayM
 array2 = 0x102a04550 class = __NSSingleObjectArrayI
 array3 = 0x102a04570 class = __NSArrayM

======== 数组内元素 ======== 
 array1[0] = 0x102a042c0 class = Person
 array2[0] = 0x102a042c0 class = Person
 array3[0] = 0x102a042c0 class = Person
复制代码

我们发现数组对象已经被深拷贝，但数组对象内的元素还是浅拷贝

是不是我们在定义Person类的时候没有重写方法呢？我们把改一下Person类的代码，并对NSMutableArray内元素进行copy

//
//  Person.m
//  AlgorithmDemo
//
//  Created by Ternence on 2021/5/9.
//

#import "Person.h"

@interface Person ()<NSCopying, NSMutableCopying>
@end

@implementation Person

- (id)copyWithZone:(NSZone *)zone {
    Person *person = [Person allocWithZone:zone];
    person.nickname = self.nickname;
    return person;
}

- (id)mutableCopyWithZone:(NSZone *)zone {
    Person *person = [Person allocWithZone:zone];
    person.nickname = self.nickname;
    return self;
}
@end
复制代码

测试代码

    Person *person = [[Person alloc] init];
    person.nickname = @"码代码的小马";
    
    NSMutableArray *array1 = [NSMutableArray arrayWithObjects:person, nil];
    
    NSArray *array2 = [array1 copy];
    NSMutableArray *array3 = [array1 mutableCopy];
    NSMutableArray *array4 = [[NSMutableArray alloc] initWithArray:array1 copyItems:true];
    NSMutableArray *array5 = [[NSMutableArray alloc] initWithObjects:[array1[0] copy], nil];

NSLog(@"\n array1 = %p class = %@", array1, [array1 class]);
    NSLog(@"\n array2 = %p class = %@", array2, [array2 class]);
    NSLog(@"\n array3 = %p class = %@", array3, [array3 class]);
    NSLog(@"\n array4 = %p class = %@", array4, [array4 class]);
    NSLog(@"\n array5 = %p class = %@", array5, [array5 class]);
    
    NSLog(@"\n\n======== 数组内元素 ======== ");
    NSLog(@"\n array1[0] = %p class = %@", array1[0], [array1[0] class]);
    NSLog(@"\n array2[0] = %p class = %@", array2[0], [array2[0] class]);
    NSLog(@"\n array3[0] = %p class = %@", array3[0], [array3[0] class]);
    
    NSLog(@"\n\n======== 数组内元素1 ========");
    Person *orgArrayObj = (Person *)array1[0];
    Person *newArrayObj = (Person *)array4[0];
    Person *newArrayObj5 = (Person *)array5[0];
    NSLog(@"\n array1[0] = %p class = %@ nickname = %p", orgArrayObj, [orgArrayObj class], orgArrayObj.nickname);
    NSLog(@"\n array4[0] = %p class = %@ nickname = %p", newArrayObj, [newArrayObj class], newArrayObj.nickname);
    NSLog(@"\n array5[0] = %p class = %@ nickname = %p", newArrayObj5, [newArrayObj5 class], newArrayObj5.nickname);
复制代码

继续查看打印结果

2021-05-09 12:10:28.436585+0800 AlgorithmDemo[23153:133313] 
 array1 = 0x1032043c0 class = __NSArrayM
 array2 = 0x1032044f0 class = __NSSingleObjectArrayI
 array3 = 0x103204510 class = __NSArrayM
 array4 = 0x103204690 class = __NSArrayM
 array5 = 0x1032046e0 class = __NSArrayM

======== 数组内元素 ======== 
 array1[0] = 0x103204880 class = Person
 array2[0] = 0x103204880 class = Person
 array3[0] = 0x103204880 class = Person

======== 数组内元素1 ========
 array1[0] = 0x103204880 class = Person nickname = 0x1000083a0
 array4[0] = 0x103204680 class = Person nickname = 0x1000083a0
 array5[0] = 0x1032046d0 class = Person nickname = 0x1000083a0
复制代码

我们再根据打印归纳总结一下
对于重写copyWithZone:、mutableCopyWithZone:的自定义对象

[array copy]、[array mutableCopy] 只深拷贝了array对象，元素是浅拷贝
initWithArray:array1 copyItems:生成了新的array，且array内元素person是深拷贝，但person的属性仍然是浅拷贝
我们分别用遍历copy array内自定义对象person生成新array的方法，自定义倒是深拷贝了，但自定义对象person的属性nickname仍然是浅拷贝

看到此处你可能会很绝望，我也很绝望…到底怎么样才能深拷贝array对象及其元素呢?

我们再试试归档的方法
先改一下person类

//
//  Person.m
//  AlgorithmDemo
//
//  Created by Ternence on 2021/5/9.
//

#import "Person.h"

@interface Person ()<NSCopying, NSMutableCopying, NSCoding>

@end

@implementation Person

- (id)copyWithZone:(NSZone *)zone {
    Person *person = [Person allocWithZone:zone];
    person.nickname = self.nickname;
    return person;
}

- (id)mutableCopyWithZone:(NSZone *)zone {
    Person *person = [Person allocWithZone:zone];
    person.nickname = self.nickname;
    return self;
}

- (instancetype)initWithCoder:(NSCoder *)coder {
    self.nickname = [coder decodeObjectForKey:@"nickname"];
    return  self;
}

- (void)encodeWithCoder:(NSCoder *)coder {
    [coder encodeObject:self.nickname forKey:@"nickname"];
}

@end

复制代码

再改写测试代码

    Person *person = [[Person alloc] init];
    person.nickname = @"码代码的小马";
    
    NSMutableArray *array1 = [NSMutableArray arrayWithObjects:person, nil];
    
    NSArray *array2 = [array1 copy];
    NSMutableArray *array3 = [array1 mutableCopy];
    NSMutableArray *array4 = [[NSMutableArray alloc] initWithArray:array1 copyItems:true];
    NSMutableArray *array5 = [[NSMutableArray alloc] initWithObjects:[array1[0] copy], nil];
    
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array1];
    NSMutableArray *array6 = [NSKeyedUnarchiver unarchiveObjectWithData:data];
    
    NSLog(@"\n array1 = %p class = %@", array1, [array1 class]);
    NSLog(@"\n array2 = %p class = %@", array2, [array2 class]);
    NSLog(@"\n array3 = %p class = %@", array3, [array3 class]);
    NSLog(@"\n array4 = %p class = %@", array4, [array4 class]);
    NSLog(@"\n array5 = %p class = %@", array5, [array5 class]);
    
    NSLog(@"\n\n======== 数组内元素 ======== ");
    NSLog(@"\n array1[0] = %p class = %@", array1[0], [array1[0] class]);
    NSLog(@"\n array2[0] = %p class = %@", array2[0], [array2[0] class]);
    NSLog(@"\n array3[0] = %p class = %@", array3[0], [array3[0] class]);
    
    NSLog(@"\n\n======== 数组内元素1 ========");
    Person *orgArrayObj = (Person *)array1[0];
    Person *newArrayObj = (Person *)array4[0];
    Person *newArrayObj5 = (Person *)array5[0];
    Person *newArrayObj6 = (Person *)array6[0];
    NSLog(@"\n array1[0] = %p class = %@ nickname = %p", orgArrayObj, [orgArrayObj class], orgArrayObj.nickname);
    NSLog(@"\n array4[0] = %p class = %@ nickname = %p", newArrayObj, [newArrayObj class], newArrayObj.nickname);
    NSLog(@"\n array5[0] = %p class = %@ nickname = %p", newArrayObj5, [newArrayObj5 class], newArrayObj5.nickname);
    NSLog(@"\n array6[0] = %p class = %@ nickname = %p", newArrayObj6, [newArrayObj6 class], newArrayObj6.nickname);
复制代码

再耐心查看一下打印

2021-05-09 12:15:28.206176+0800 AlgorithmDemo[23739:137444] 
 array1 = 0x10054bf80 class = __NSArrayM
 array2 = 0x10053f290 class = __NSSingleObjectArrayI
 array3 = 0x10054c0b0 class = __NSArrayM
 array4 = 0x10054c220 class = __NSArrayM
 array5 = 0x10054c250 class = __NSArrayM

======== 数组内元素 ======== 
 array1[0] = 0x10054b890 class = Person
 array2[0] = 0x10054b890 class = Person
 array3[0] = 0x10054b890 class = Person

======== 数组内元素1 ========
 array1[0] = 0x10054b890 class = Person nickname = 0x1000083a0
 array4[0] = 0x10053dc30 class = Person nickname = 0x1000083a0
 array5[0] = 0x10053de20 class = Person nickname = 0x1000083a0
 array6[0] = 0x10054d300 class = Person nickname = 0x100548f00
复制代码

是的，我们成功了,归解档后，array对象深拷贝了，array内的自定义对象person深拷贝了，自定义对象person的nickname也深拷贝了

我们来对Array的拷贝做个年终总结:

copy：对NSArray对象是浅拷贝，可NSMutableArray对象是深拷贝
mutableCopy：始终是深拷贝
copy、mutable对array内的元素是浅拷贝
initWithArray:array1 copyItems:生成了新的array，且array内元素person是深拷贝，但person的属性nickname仍然是浅拷贝
通过归解档的方式，可以实现对array 、array 内元素person、person属性nickname深拷贝