谓词中对象的字典属性的元素的键路径？
简而言之，我正在寻找正确的谓词格式来索引对象的字典属性。
我有一个 myObject 实例数组，每个实例都有一个属性 CPDictionary(NSMutableDictionary) extAttributes，我试图允许根据 extAttributes 中的值进行过滤。我定义我的谓词如下，
[CPPredicate predicateWithFormat:@"extAttributes[%K] like[c] %@",key,val]
我不确定正确的键路径是什么。阅读 NSPredicate 上的文档，似乎“extAttributes[%k]”可能是数组的索引，而不是字典。我尝试了几种替代方案，这是唯一一个不会出错的方案。检查结果对象时，谓词对象中的表达式似乎是正确的。然而，它没有达到预期的结果。
In short, I am looking for the correct predicate format to index into a dictionary attribute on an object.
I have an array of myObject instances, each with an attribute CPDictionary(NSMutableDictionary) extAttributes and I am trying to allow filtering based on values in extAttributes. I am defining my predicate as follows
[CPPredicate predicateWithFormat:@"extAttributes[%K] like[c] %@",key,val]
I am not sure what the correct key-path would be for this. Reading the documentation on NSPredicate it would seem that "extAttributes[%k]" might be an index into an array, not a dictionary. I have tried several alternatives and this is the only one that doesn't error. When inspecting the resulting objects, the expressions in the predicate object appear to be correct. However, it doesn't have the intended result.
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看起来您可能会混淆数组和字典引用。只需使用关键路径（点分隔的元素名称）来引用嵌套元素或对象属性，概念上是这样的：
话又说回来，我对卡布奇诺不太熟悉，所以我不确定他们是否已经完成了这里略有不同，但这就是 Cocoa 和 Cocoa touch 中的工作方式。
编辑
要动态计算密钥，您需要做的就是编写一个密钥路径字符串：
您现在可以按如下方式创建谓词：
编辑
Cocoa/Cocoa 中的等效代码触摸将是：
It looks like you might be confusing array and dictionary references. Just use a key path (dot-separated element names) to refer to nested elements or object properties, conceptually something like this:
Then again, I'm not all that familiar with Cappuccino, so I'm not sure if they've done something slightly different here, but this is the way it works in Cocoa and Cocoa touch.
EDIT
To compute the key dynamically, all you need to do is compose a key path string:
You can now create the predicate as follows:
EDIT
The equivalent code in Cocoa/Cocoa touch would be: