ios - 替换嵌套 NSDictionary 中出现的 NSNull

Question

这个问题类似于this question ，但是此方法仅适用于字典的根级别。

我正在寻找用空字符串替换任何出现的 NSNull 值，这样我就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'不写)。

但是，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
    };
};

有没有办法从所有字典(包括嵌套字典)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(我不想每次提要更改时都必须更新应用程序)。

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，快速枚举现在在 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" = "";
    };