替换嵌套 NSDictionary 中出现的 NSNull
Posted
技术标签:
【中文标题】替换嵌套 NSDictionary 中出现的 NSNull【英文标题】：Replace occurrences of NSNull in nested NSDictionary 【发布时间】：2012-08-31 10:49:07 【问题描述】：这个问题类似于this question，但是这个方法只适用于字典的根级别。
我希望用空字符串替换任何出现的NSNull 值，以便我可以将完整的字典保存到 plist 文件中（如果我将它与 NSNull 一起添加，文件将不会写入）。
然而，我的字典里面有嵌套的字典。像这样：
"dictKeyName" =
innerStrKeyName = "This is a string in a dictionary";
innerNullKeyName = "<null>";
innerDictKeyName =
"innerDictStrKeyName" = "This is a string in a Dictionary in another Dictionary";
"innerDictNullKeyName" = "<null>";
;
;
如果我使用：
@interface NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings;
@end
@implementation NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings
const NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:self];
const id nul = [NSNull null];
const NSString *blank = @"";
for(NSString *key in replaced)
const id object = [self objectForKey:key];
if(object == nul)
[replaced setObject:blank forKey:key];
return [NSDictionary dictionaryWithDictionary:replaced];
@end
我得到这样的东西：
"dictKeyName" =
innerStrKeyName = "This is a string in a dictionary";
innerNullKeyName = ""; <-- this value has changed
innerDictKeyName =
"innerDictStrKeyName" = "This is a string in a Dictionary in another Dictionary";
"innerDictNullKeyName" = "<null>"; <-- this value hasn't changed
;
;
有没有办法从包括嵌套字典在内的所有字典中找到每个 NSNull 值...？
编辑： 数据是从 JSON 提要中提取的，因此我收到的数据是动态的（我不想在每次提要更改时都更新应用程序）。
【问题讨论】：
另外你真的应该发布实际代码 "对该方法稍加修改即可使其递归：
@interface NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings;
@end
@implementation NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings
const NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary: self];
const id nul = [NSNull null];
const NSString *blank = @"";
for (NSString *key in self)
const id object = [self objectForKey: key];
if (object == nul)
[replaced setObject: blank forKey: key];
else if ([object isKindOfClass: [NSDictionary class]])
[replaced setObject: [(NSDictionary *) object dictionaryByReplacingNullsWithStrings] forKey: key];
return [NSDictionary dictionaryWithDictionary: replaced];
请注意，快速枚举现在位于 self 而不是 replaced
使用上面的代码，这个例子：
NSMutableDictionary *dic1 = [NSMutableDictionary dictionary];
[dic1 setObject: @"string 1" forKey: @"key1.1"];
[dic1 setObject: [NSNull null] forKey: @"key1.2"];
NSMutableDictionary *dic2 = [NSMutableDictionary dictionary];
[dic2 setObject: @"string 2" forKey: @"key2.1"];
[dic2 setObject: [NSNull null] forKey: @"key2.2"];
[dic1 setObject: dic2 forKey: @"key1.3"];
NSLog(@"%@", dic1);
NSLog(@"%@", [dic1 dictionaryByReplacingNullsWithStrings]);
呈现这个结果：
2012-09-01 08:30:16.210 Test[57731:c07]
"key1.1" = "string 1";
"key1.2" = "<null>";
"key1.3" =
"key2.1" = "string 2";
"key2.2" = "<null>";
;
2012-09-01 08:30:16.212 Test[57731:c07]
"key1.1" = "string 1";
"key1.2" = "";
"key1.3" =
"key2.1" = "string 2";
"key2.2" = "";
;
【讨论】：
真的吗？我在其输出中添加了一个使用示例。 最后一行是多余的；改为return replaced; 就足够了。
如果对象是NSArray怎么办？
如何处理嵌套的 json 字符串，见这篇文章***.com/questions/48009583/…
即使当前实现有效，我也会使用 for (NSString *key in [self allKeys]) - 因为它的可读性较差，而且您需要深入挖掘才能知道快速枚举over NSDictionary 枚举键。 （可以是值，或对，或其他任何东西。【参考方案2】：
它对我有用，我使用嵌套循环将包括 NSArray 在内的整个字典中的所有 NULL 替换为 nil。
- (NSDictionary *) dictionaryByReplacingNullsWithNil:(NSDictionary*)sourceDictionary
NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:sourceDictionary];
const id nul = [NSNull null];
for(NSString *key in replaced)
const id object = [sourceDictionary objectForKey:key];
if(object == nul)
[replaced setValue:nil forKey:key];
return [NSDictionary dictionaryWithDictionary:replaced];
-(NSDictionary *) nestedDictionaryByReplacingNullsWithNil:(NSDictionary*)sourceDictionary
NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:sourceDictionary];
const id nul = [NSNull null];
const NSString *blank = @"";
[sourceDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id object, BOOL *stop)
object = [sourceDictionary objectForKey:key];
if([object isKindOfClass:[NSDictionary class]])
NSDictionary *innerDict = object;
[replaced setObject:[self nestedDictionaryByReplacingNullsWithNil:innerDict] forKey:key];
else if([object isKindOfClass:[NSArray class]])
NSMutableArray *nullFreeRecords = [NSMutableArray array];
for (id record in object)
if([record isKindOfClass:[NSDictionary class]])
NSDictionary *nullFreeRecord = [self nestedDictionaryByReplacingNullsWithNil:record];
[nullFreeRecords addObject:nullFreeRecord];
[replaced setObject:nullFreeRecords forKey:key];
else
if(object == nul)
[replaced setObject:blank forKey:key];
];
return [NSDictionary dictionaryWithDictionary:replaced];
【讨论】：
这个实现比公认的更有用，因为它考虑了数组 此实现不会考虑包含非字典数据（例如字符串或数组）的数组。它将返回一个空数组 对不起...但是 [someMutableDictionary setValue:nil forKey @"someKey"] 不会在字典中引入 nil - 这会立即崩溃。相反，它完全删除了键/值对。我不确定这是否能很好地满足 OP 的需求【参考方案3】：如果有人在 swift 1.2 中需要这个，这里是 sn-p：
class func removeNullsFromDictionary(origin:[String:AnyObject]) -> [String:AnyObject]
var destination:[String:AnyObject] = [:]
for key in origin.keys
if origin[key] != nil && !(origin[key] is NSNull)
if origin[key] is [String:AnyObject]
destination[key] = self.removeNullsFromDictionary(origin[key] as! [String:AnyObject])
else if origin[key] is [AnyObject]
let orgArray = origin[key] as! [AnyObject]
var destArray: [AnyObject] = []
for item in orgArray
if item is [String:AnyObject]
destArray.append(self.removeNullsFromDictionary(item as! [String:AnyObject]))
else
destArray.append(item)
destination[key] = destArray
else
destination[key] = origin[key]
else
destination[key] = ""
return destination
【讨论】：
有效，但您忘记了循环结束时的 destination[key] = destArray @Danilo，感谢您的评论，我编辑了 sn-p【参考方案4】：以下方法适用于任意数量的嵌套字典数组：
- (NSMutableDictionary *)dictionaryByReplacingNullsWithStrings:(NSDictionary *)jobList
NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:jobList];
const id nul = [NSNull null];
const NSString *blank = @"";
for (NSString *key in [replaced allKeys])
id object = [replaced objectForKey:key];
if (object == nul)
[replaced setObject:blank
forKey:key];
else
if ([object isKindOfClass:[NSDictionary class]])
[replaced setObject:[self replaceNullInNested:object]
forKey:key];
else
if ([object isKindOfClass:[NSArray class]])
NSMutableArray *dc = [[NSMutableArray alloc] init];
for (NSDictionary *tempDict in object)
[dc addObject:[self dictionaryByReplacingNullsWithStrings:tempDict]];
[replaced setObject:dc
forKey:key];
return replaced;
- (NSMutableDictionary *)replaceNullInNested:(NSDictionary *)targetDict
// make it to be NSMutableDictionary in case that it is nsdictionary
NSMutableDictionary *m = [targetDict mutableCopy];
NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:m];
const id nul = [NSNull null];
const NSString *blank = @"";
for (NSString *key in [replaced allKeys])
const id object = [replaced objectForKey:key];
if (object == nul)
[replaced setObject:blank
forKey:key];
else
if ([object isKindOfClass:[NSArray class]])
// NSLog(@"found null inside and key is %@", key);
// make it to be able to set value by create a new one
NSMutableArray *a = [object mutableCopy];
for (int i = 0; i < [a count]; i++)
for (NSString *subKey in [[a objectAtIndex:i] allKeys])
if ([[object objectAtIndex:i] valueForKey:subKey] == nul)
[[object objectAtIndex:i] setValue:blank
forKey:subKey];
// replace the updated one with old one
[replaced setObject:a
forKey:key];
return replaced;
我根据需要的功能使用了上述修改方法：
//调用方法
NSMutableDictionary *sortedDict = [[NSMutableDictionary alloc] init];
for (NSString *key in jobList)
NSMutableArray *tempArray = [[NSMutableArray alloc] init];
for (NSDictionary *tempDict in [jobList objectForKey:key])
[tempArray addObject:[self dictionaryByReplacingNullsWithStrings:tempDict]];
[sortedDict setObject:tempArray forKey:key];
【讨论】：
【参考方案5】：这段代码
@interface NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings;
@end
Monkey 补丁 NSDictionary - 这意味着您可以调用 dictionaryByReplace... 不仅在根目录上，而且在任何嵌套字典上都可以。
从设计的角度来看，我真的不同意这一点，但它确实解决了你的问题。
【讨论】：
这个我知道，但是我的数据是动态的，所以我不想每次更新字典都重新发布代码。 检查对象是否为字典，并替换为调用方法的结果。【参考方案6】：试试这个：
@interface NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings;
-(NSDictionary *) nestedDictionaryByReplacingNullsWithStrings;
@end
@implementation NSDictionary (JRAdditions)
- (NSDictionary *) dictionaryByReplacingNullsWithStrings
const NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:self];
const id nul = [NSNull null];
const NSString *blank = @"";
for(NSString *key in replaced)
const id object = [self objectForKey:key];
if(object == nul)
[replaced setObject:blank forKey:key];
return [NSDictionary dictionaryWithDictionary:replaced];
-(NSDictionary *) nestedDictionaryByReplacingNullsWithStrings
const NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary:self];
const id nul = [NSNull null];
const NSString *blank = @"";
for(id *item in replaced)
const id object = [self objectForKey:key];
if([object isKindofClass:[NSDictionary class]])
NSDictionary *innerDict = object;
[replaced setObject:[innerDict dictionaryByReplacingNullsWithStrings] forKey:key];
else
if(object == nul)
[replaced setObject:blank forKey:key];
return [NSDictionary dictionaryWithDictionary:replaced];
【讨论】：
【参考方案7】：此解决方案适用于数组和字典，也适用于嵌套数组和字典等（递归）。
- (NSDictionary *)writableDictionary:(NSDictionary *)dictionary
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:dictionary];
for (id key in mutableDictionary.allKeys)
id value = mutableDictionary[key];
mutableDictionary[key] = [self writableValue:value];
return mutableDictionary;
- (NSArray *)writableArray:(NSArray *)array
NSMutableArray *mutableArray = [NSMutableArray arrayWithArray:array];
for (int i = 0; i < mutableArray.count; ++i)
id value = mutableArray[i];
mutableArray[i] = [self writableValue:value];
return mutableArray;
- (id)writableValue:(id)value
if ([value isKindOfClass:[NSNull class]])
value = @"";
else if ([value isKindOfClass:[NSDictionary class]])
value = [self writableDictionary:value];
else if ([value isKindOfClass:[NSArray class]])
value = [self writableArray:value];
return value;
【讨论】：
【参考方案8】：如果您的字典中有数组，上述答案不适合这种情况。看看这个
+(NSMutableDictionary*)getValuesWithOutNull:(NSDictionary
*)yourDictionary
NSMutableDictionary *replaced = [NSMutableDictionary
dictionaryWithDictionary: yourDictionary];
id nul = [NSNull null];
NSString *blank = @"";
for (NSString *key in yourDictionary)
const id object = [yourDictionary objectForKey: key];
if (object == nul)
[replaced setObject: blank forKey: key];
else if ([object isKindOfClass: [NSDictionary class]])
[replaced setObject:[self getValuesWithOutNull:object]
forKey:key];
else if([object isKindOfClass: [NSArray class]])
NSMutableArray *array = [NSMutableArray
arrayWithArray:object];
for(int i = 0 ;i < array.count;i++)
NSDictionary *dict = [array objectAtIndex:i];
[array replaceObjectAtIndex:i withObject:[self
getValuesWithOutNull:dict]];
[replaced setObject:array forKey:key];
return replaced;
【讨论】：
以上是关于替换嵌套 NSDictionary 中出现的 NSNull的主要内容，如果未能解决你的问题，请参考以下文章
PHP json_encode() 与空 NSDictionary
如何在 PLIST 中访问嵌套的 NSDictionary？
IOS 中NSDictionary 与 Dictionary 有啥区别
从 CoreData 在 NSDictionary 中制作嵌套 JSON