问题:有没有一种方法可以使用现有的 Objective-C 方法来对 NSDictionary 或 NSArray 进行完整的深层复制,而它们本身也有嵌套的字典或数组?
那是我读到的问题可能是当它遇到嵌套字典或数组时,它只复制指向嵌套项目的指针,而不是真正复制该项目。
背景:作为我的一个例子,我尝试使用 NSUserDefaults 加载/保存以下配置,并且在加载时需要将从 NSUserDefault 获取的不可变副本转换为可变副本,然后再进行更改。
- 项目(NSDictionary)
- 项目(NSDictionary)
- aString: NSString
- aString2:NSString
- 日期:NSDate
- aDate2:NSDate
- aBool: BOOL
- aTI1:NSTimeInterval
- aTI2:NSTimeInterval
- 关键字 (NSArray)
- 关键字:NSString
- 关键字:NSString
- 项目(NSDictionary)
最佳答案
几年前,我出于完全相同的原因编写了一些类别方法,将整个用户默认树转换为可变的。它们就在这里——使用它们需要您自担风险! :-)
//
// SPDeepCopy.h
//
// Created by Sherm Pendley on 3/15/09.
//
#import <Cocoa/Cocoa.h>
// Deep -copy and -mutableCopy methods for NSArray and NSDictionary
@interface NSArray (SPDeepCopy)
- (NSArray*) deepCopy;
- (NSMutableArray*) mutableDeepCopy;
@end
@interface NSDictionary (SPDeepCopy)
- (NSDictionary*) deepCopy;
- (NSMutableDictionary*) mutableDeepCopy;
@end
<小时/>
//
// SPDeepCopy.m
//
// Created by Sherm Pendley on 3/15/09.
//
#import "SPDeepCopy.h"
@implementation NSArray (SPDeepCopy)
- (NSArray*) deepCopy {
unsigned int count = [self count];
id cArray[count];
for (unsigned int i = 0; i < count; ++i) {
id obj = [self objectAtIndex:i];
if ([obj respondsToSelector:@selector(deepCopy)])
cArray[i] = [obj deepCopy];
else
cArray[i] = [obj copy];
}
NSArray *ret = [[NSArray arrayWithObjects:cArray count:count] retain];
// The newly-created array retained these, so now we need to balance the above copies
for (unsigned int i = 0; i < count; ++i)
[cArray[i] release];
return ret;
}
- (NSMutableArray*) mutableDeepCopy {
unsigned int count = [self count];
id cArray[count];
for (unsigned int i = 0; i < count; ++i) {
id obj = [self objectAtIndex:i];
// Try to do a deep mutable copy, if this object supports it
if ([obj respondsToSelector:@selector(mutableDeepCopy)])
cArray[i] = [obj mutableDeepCopy];
// Then try a shallow mutable copy, if the object supports that
else if ([obj respondsToSelector:@selector(mutableCopyWithZone:)])
cArray[i] = [obj mutableCopy];
// Next try to do a deep copy
else if ([obj respondsToSelector:@selector(deepCopy)])
cArray[i] = [obj deepCopy];
// If all else fails, fall back to an ordinary copy
else
cArray[i] = [obj copy];
}
NSMutableArray *ret = [[NSMutableArray arrayWithObjects:cArray count:count] retain];
// The newly-created array retained these, so now we need to balance the above copies
for (unsigned int i = 0; i < count; ++i)
[cArray[i] release];
return ret;
}
@end
@implementation NSDictionary (SPDeepCopy)
- (NSDictionary*) deepCopy {
unsigned int count = [self count];
id cObjects[count];
id cKeys[count];
NSEnumerator *e = [self keyEnumerator];
unsigned int i = 0;
id thisKey;
while ((thisKey = [e nextObject]) != nil) {
id obj = [self objectForKey:thisKey];
if ([obj respondsToSelector:@selector(deepCopy)])
cObjects[i] = [obj deepCopy];
else
cObjects[i] = [obj copy];
if ([thisKey respondsToSelector:@selector(deepCopy)])
cKeys[i] = [thisKey deepCopy];
else
cKeys[i] = [thisKey copy];
++i;
}
NSDictionary *ret = [[NSDictionary dictionaryWithObjects:cObjects forKeys:cKeys count:count] retain];
// The newly-created dictionary retained these, so now we need to balance the above copies
for (unsigned int i = 0; i < count; ++i) {
[cObjects[i] release];
[cKeys[i] release];
}
return ret;
}
- (NSMutableDictionary*) mutableDeepCopy {
unsigned int count = [self count];
id cObjects[count];
id cKeys[count];
NSEnumerator *e = [self keyEnumerator];
unsigned int i = 0;
id thisKey;
while ((thisKey = [e nextObject]) != nil) {
id obj = [self objectForKey:thisKey];
// Try to do a deep mutable copy, if this object supports it
if ([obj respondsToSelector:@selector(mutableDeepCopy)])
cObjects[i] = [obj mutableDeepCopy];
// Then try a shallow mutable copy, if the object supports that
else if ([obj respondsToSelector:@selector(mutableCopyWithZone:)])
cObjects[i] = [obj mutableCopy];
// Next try to do a deep copy
else if ([obj respondsToSelector:@selector(deepCopy)])
cObjects[i] = [obj deepCopy];
// If all else fails, fall back to an ordinary copy
else
cObjects[i] = [obj copy];
// I don't think mutable keys make much sense, so just do an ordinary copy
if ([thisKey respondsToSelector:@selector(deepCopy)])
cKeys[i] = [thisKey deepCopy];
else
cKeys[i] = [thisKey copy];
++i;
}
NSMutableDictionary *ret = [[NSMutableDictionary dictionaryWithObjects:cObjects forKeys:cKeys count:count] retain];
// The newly-created dictionary retained these, so now we need to balance the above copies
for (unsigned int i = 0; i < count; ++i) {
[cObjects[i] release];
[cKeys[i] release];
}
return ret;
}
@end
关于iphone - 如何对具有嵌套数组/字典的 NSArray 和 NSDictionary 进行真正的深度复制?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5453481/