将对象从一个NSMutableArray复制到另一个NSMutableArray(copy objects from one NSMutableArray to another NSMutableArray)

 我试图理解从一个NSMutableArray复制对象到另一个NSMutableArray。 请考虑以下两种情况：1 - 将原始文件复制到克隆，其中克隆中的更改将影响原始文件。 2 - 将原件复制到克隆，其中关闭的更改不会影响原件。 
 
 首先，我尝试使用以下代码首先生成场景＃1。 根据我的理解，当复制数组不使用'mutablecopy'时，克隆数组将只保存指向原始字符串对象的指针。 所以，如果我要将克隆的第一个元素更改为另一个对象，原始的第一个元素会改变得太对吗？ ......但这不是我得到的结果。 为什么？ 
 
 事实上，当我使用mutablecopy时 
 
[self.cloneArray addObject:[[self.originalArray objectAtIndex:i] mutableCopy]];
 
 我得到了相同的结果。 我很困惑。 
 
 ArrayClass.h 
 
@interface ArrayClass : NSObject {
    NSMutableArray *_originalArray;
    NSMutableArray *_cloneArray;
}

@property (nonatomic, retain) NSMutableArray *originalArray;
@property (nonatomic, retain) NSMutableArray *cloneArray;
 
 ArrayClass.m 
 
@synthesize originalArray = _originalArray;
@synthesize cloneArray = _cloneArray;

_originalArray = [[NSMutableArray alloc] initWithObjects: @"one", @"two", @"three", @"four", @"five", nil];
_cloneArray = [[NSMutableArray alloc] initWithCapacity:[self.originalArray count]];

for (int i=0; i<5; i++) {
    [self.cloneArray addObject:[self.originalArray objectAtIndex:i]];
}

// make change to the first element of the clone array
[self.cloneArray replaceObjectAtIndex:0 withObject:@"blah"];

for (int n=0; n<5; n++) {
    NSLog(@"Original:%@ --- Clone:%@", [self.originalArray objectAtIndex:n], [self.cloneArray objectAtIndex:n]);
}
 
 ... 
 
2011-03-27 03:23:16.637 StringTest[1751:207] Original:one --- Clone:blah
2011-03-27 03:23:16.638 StringTest[1751:207] Original:two --- Clone:two
2011-03-27 03:23:16.639 StringTest[1751:207] Original:three --- Clone:three
2011-03-27 03:23:16.642 StringTest[1751:207] Original:four --- Clone:four
2011-03-27 03:23:16.643 StringTest[1751:207] Original:five --- Clone:five

I am trying to understand copying objects from one NSMutableArray to another. Consider the following 2 scenarios: 1 - copying original to clone where changes in the clone will affect the original. 2 - copying original to clone where the changes in the close will NOT affect the original.
 
First, I am trying to produce scenario #1 first with the following code. From what I understand, when copying array not using 'mutablecopy', the clone array will just hold the pointer to the same string objects in the original. So if I were to change the first element of the clone to a different object, the first element of the original would change too right? ... but that's not the result I am getting. Why?
 
Matter of fact, when I use mutablecopy 
 
[self.cloneArray addObject:[[self.originalArray objectAtIndex:i] mutableCopy]];
 
I get the same result. I am confused.
 
ArrayClass.h
 
@interface ArrayClass : NSObject {
    NSMutableArray *_originalArray;
    NSMutableArray *_cloneArray;
}

@property (nonatomic, retain) NSMutableArray *originalArray;
@property (nonatomic, retain) NSMutableArray *cloneArray;
 
ArrayClass.m
 
@synthesize originalArray = _originalArray;
@synthesize cloneArray = _cloneArray;

_originalArray = [[NSMutableArray alloc] initWithObjects: @"one", @"two", @"three", @"four", @"five", nil];
_cloneArray = [[NSMutableArray alloc] initWithCapacity:[self.originalArray count]];

for (int i=0; i<5; i++) {
    [self.cloneArray addObject:[self.originalArray objectAtIndex:i]];
}

// make change to the first element of the clone array
[self.cloneArray replaceObjectAtIndex:0 withObject:@"blah"];

for (int n=0; n<5; n++) {
    NSLog(@"Original:%@ --- Clone:%@", [self.originalArray objectAtIndex:n], [self.cloneArray objectAtIndex:n]);
}
 
...
 
2011-03-27 03:23:16.637 StringTest[1751:207] Original:one --- Clone:blah
2011-03-27 03:23:16.638 StringTest[1751:207] Original:two --- Clone:two
2011-03-27 03:23:16.639 StringTest[1751:207] Original:three --- Clone:three
2011-03-27 03:23:16.642 StringTest[1751:207] Original:four --- Clone:four
2011-03-27 03:23:16.643 StringTest[1751:207] Original:five --- Clone:five

原文：https://stackoverflow.com/questions/5447853