问题
I want to use valueForKeyPath on my NSDictionary, but the problem is that one of the keys is a string that starts with the @ symbol. I have no control over the naming of the key.
I'm having problems trying to create the key path as I'm getting a format exception, even when trying to escape the @ symbol:
This works fine:
[[[dict objectForKey:@"key1"] objectForKey:@"@specialKey"] objectForKey:@"key3"]
However none of these work:
[dict valueForKeyPath:@"key1.@specialKey.key3"]
[dict valueForKeyPath:@"key1.@@specialKey.key3"]
Any ideas?
Thanks,
Mike
回答1:
you shouldn't be using @ signs with your key names if you want to use key value coding.
apple's guidelines for key names are as follows:
Keys must use ASCII encoding, begin with a lowercase letter, and may not contain whitespace.
You'll have to find a workaround to reformat the key string whereever you're getting your keys from to be KVC compliant.
回答2:
Just to update this old question a little...
The reason that these:
[dict valueForKeyPath:@"key1.@specialKey.key3"]
[dict valueForKeyPath:@"key1.@@specialKey.key3"]
...fail is that any "@" symbols in a key path are interpreted as being collection's operators as with:
[dict valueForKeyPath:@"key1.@sum.key3"] // returns the sum of all 'key3' values
[dict valueForKeyPath:@"key1.@avg.key3"] // returns the average of all 'key3' values
The nested key calls:
[[[dict objectForKey:@"key1"] objectForKey:@"@specialKey"] objectForKey:@"key3"]
... work because a single key is not processed as a key path.
回答3:
If you have no control over the naming, how about adding a category with a properly named key that simply returns/sets the weird key?
回答4:
I see that there are 2 ways
Swizzle
You can swizzle the valueForKeyPath on NSDictionary to remove the @ symbol, remember to account for @sum, @average, ...
Override if you're using Mantle
Override + (id)modelOfClass:(Class)modelClass fromJSONDictionary:(NSDictionary *)JSONDictionary on MTLJSONAdapter, traverse all the keys and remove the @ symbol
来源：https://stackoverflow.com/questions/1567850/using-valueforkeypath-on-nsdictionary-if-a-key-starts-the-symbol