NSDictionary Predicate filter on child objects

问题:

I'm trying to filter a response from Facebook's API, the JSON looks like this:

{ 
 "Data": [
  {  
    "first_name" : "Joe",
    "last_name" : "bloggs",
    "uuid" : "123"
  },
  {  
    "first_name" : "johnny",
    "last_name" : "appleseed",
    "uuid" : "321"
  }
 ]
}

I load this into a NSDictionary, accessing it like [[friendDictionary objectForKey:@"data"] allObjects]

I'm now trying to filter based on the first_name and last_name based on when someone inputs a name into a textfield. Here's what I have but its failing horribly:

  NSPredicate *filter = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"ANY.first_name beginswith[c] %@ OR ANY.last_name beginswith[c] %@", friendField.text, friendField.text]];
  NSLog(@"%@", [[[friendDictionary objectForKey:@"data"] allObjects] filteredArrayUsingPredicate:filter]);

Any help is greatly appreciated, thanks guys

回答1:

You are thinking too complicated.

• stringWithFormat within predicateWithFormat makes no sense here.
• No need for the "ANY" aggregate in the predicate, that is used with to-many-relationships in Core Data objects.
• [friendDictionary objectForKey:@"Data"] returns an array, allObjects is wrong here.
• The key is "Data", not "data".

That gives

NSPredicate *filter = [NSPredicate predicateWithFormat:@"first_name beginswith[c] %@ OR last_name beginswith[c] %@",
    friendField.text, friendField.text];
NSArray *filteredArray = [[friendDictionary objectForKey:@"Data"] filteredArrayUsingPredicate:filter];