通常需要實現(xiàn)對模型的拷貝都需要先實現(xiàn)NSCopying、 NSMutableCopying協(xié)議，在這里我一直有個誤區(qū)，以為實現(xiàn)了copying協(xié)議，數(shù)組使用拷貝操作都會對數(shù)組內(nèi)實現(xiàn)copy協(xié)議的對象進行拷貝。

創(chuàng)建兩個model并實現(xiàn)copying協(xié)議

// Dog.h
@interface Dog : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy) NSString *name;

@end

// Dog.m
@implementation Dog

- (nonnull id)copyWithZone:(nullable NSZone *)zone {
    Dog *copy = [[Dog allocWithZone:zone]init];
    copy.name = self.name;
    return copy;
}

- (id)mutableCopyWithZone:(NSZone *)zone {
    Dog *copy = [[Dog allocWithZone:zone]init];
    copy.name = self.name;
    return copy;
}

@end

// Person.h
#import "Dog.h"

@interface Person : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) NSInteger age;
@property (nonatomic, copy) Dog *dog;

@end

// Person.m
@implementation Person

- (nonnull id)copyWithZone:(nullable NSZone *)zone {
    Person *copy = [[Person allocWithZone:zone]init];
    copy.name = self.name;
    copy.age = self.age;
    copy.dog = [self.dog copy];
    return copy;
}

- (id)mutableCopyWithZone:(NSZone *)zone {
    Person *copy = [[Person allocWithZone:zone]init];
    copy.name = self.name;
    copy.age = self.age;
    copy.dog = [self.dog copy];
    return copy;
}

@end 

對模型數(shù)組使用mutablCopy操作并不是深拷貝

NSMutableArray <Person *>*dataSourceAry = [NSMutableArray new];

for (int i = 0; i < 2; i++) {
    Dog *dog = [[Dog alloc]init];
    dog.name = @"拉不拉多不多就拉倒";
    
    Person *item = [[Person alloc]init];
    item.name = @"杰克";
    item.age = 18;
    item.dog = [dog copy];
    [dataSourceAry addObject:item];
}

NSArray <Person *>*array = [dataSourceAry mutableCopy];
NSLog(@"<dataSourceAry: %@>", dataSourceAry);
NSLog(@"<array: %@>", array);


[array enumerateObjectsUsingBlock:^(Person *obj, NSUInteger idx, BOOL * _Nonnull stop) {
    obj.name = @"肉絲";
}];

NSLog(@"dataSourceAry[0].name = %@", dataSourceAry[0].name);
NSLog(@"array[0].name = %@", array[0].name);

/** 打印結(jié)果
 <dataSourceAry: ("<Person: 0x60000043ec00>", "<Person: 0x60000043e9c0>")>
 <array: ("<Person: 0x60000043ec00>","<Person: 0x60000043e9c0>")>
 dataSourceAry[0].name = 肉絲
 array[0].name = 肉絲
 */

可以從打印的結(jié)果看出，數(shù)組內(nèi)元素的內(nèi)存地址是相同的，所以出現(xiàn)了修改拷貝后數(shù)組的第一個元素，導(dǎo)致原數(shù)組的第一個元素也發(fā)生了同樣的改變。雖然兩個數(shù)組的內(nèi)存地址不一樣，但是內(nèi)部元素內(nèi)存地址還是同一地址，不是我們想要的結(jié)果。

實現(xiàn)模型數(shù)組深拷貝的方法

1、最笨的方法就是通過遍歷逐個拷貝元素

NSMutableArray *array = [NSMutableArray array];
for (Person *person in dataSourceAry) {
    [array addObject:[person copy]];
}

2、也有人使用歸檔解檔實現(xiàn)數(shù)組內(nèi)部元素拷貝

3、這么好用的一個方法現(xiàn)在才發(fā)現(xiàn)（推薦）

- (instancetype)initWithArray:(NSArray<ObjectType> *)array copyItems:(BOOL)flag 

NSArray <Person *>*deepCopyAry = [[NSArray alloc]initWithArray:dataSourceAry copyItems:YES];
NSLog(@"<dataSourceAry: %@>", dataSourceAry);
NSLog(@"<deepCopyAry: %@>", deepCopyAry);
    
[deepCopyAry enumerateObjectsUsingBlock:^(Person *obj, NSUInteger idx, BOOL * _Nonnull stop) {
    obj.name = @"弗蘭克";
    obj.dog.name = @"弗蘭克的dog";
}];

NSLog(@"dataSourceAry[0].name = %@", dataSourceAry[0].name);
NSLog(@"deepCopyAry[0].name = %@", deepCopyAry[0].name);
    
NSLog(@"dataSourceAry[0].dog.name = %@", dataSourceAry[0].dog.name);
NSLog(@"deepCopyAry[0].dog.name = %@", deepCopyAry[0].dog.name);
    
/** 打印結(jié)果
<dataSourceAry: ("<Person: 0x604000427680>", "<Person: 0x604000425220>")>
<deepCopyAry: ("<Person: 0x60000042cb80>", "<Person: 0x60000042cae0>")>
 
dataSourceAry[0].name = 肉絲
deepCopyAry[0].name = 弗蘭克
 
dataSourceAry[0].dog.name = 拉不拉多不多就拉倒
deepCopyAry[0].dog.name = 弗蘭克的dog
 */

總結(jié)

1、模型數(shù)組內(nèi)元素中模型必須要實現(xiàn)copying協(xié)議，模型內(nèi)如果有嵌套模型，也需要實現(xiàn)copying協(xié)議，否則執(zhí)行對對象拷貝操作會出現(xiàn)崩潰；
2、使用- (instancetype)initWithArray:(NSArray<ObjectType> *)array copyItems:(BOOL)flag實現(xiàn)模型數(shù)組拷貝；