在嵌套的NSDictionary中替换NSNull的出现次数

Question

这个问题类似于这个问题,但这种方法只适用于字典的根目录下.

我想NSNull用空字符串替换任何出现的值,以便我可以将完整的字典保存到plist文件(如果我用NSNull添加它,文件将不会写入).

但是,我的词典里面嵌套了词典.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
    };
};

有没有办法找到NSNull所有字典中的每个值,包括嵌套字典......？

编辑: 将数据从一个JSON料绘制,所以我接收到的数据是动态的(我不希望有更新的应用在每次改变饲料).

Answer 1

对该方法的一个小修改可以使其递归:

@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,快速枚举现在开启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]);

呈现此结果:

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" = "";
    };

Answer 2

它适用于我,我使用嵌套循环来替换整个字典中包含NSArray的所有NULL和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];  
}