从NSDictionary中提取键/值对

Question

是否有方便的方法从NSDictionary获取键/值对？

说我有一个NSDictionary，partyGuest，

{
   name = "jim";
   age = 28;
   occupation = "astronaut";
   favouriteMeal = 
      {
         starter = "fish head soup";
         mainCourse = "roast armadillo";
         dessert = "sugar plum fairy cakes";
      }
}

我希望获得一个键/值对，就像这样，

NSDictionary *guestFoodChoice = [partyGuest itemForKey:@"favouriteMeal"];

...并获得密钥和值，

   guestFoodChoice =
{
   favouriteMeal = 
      {
         starter = "fish head soup";
         mainCourse = "roast armadillo";
         dessert = "sugar plum fairy cakes";
      }
}

似乎应该有，但由于我看不到一个明显的方法，也许我错过了什么？

Answer 1

听起来你基本上想要在另一个字典中获得一个包含一些子集（可能只有一个）键值对的字典。如果这是正确的，键值编码方法dictionaryWithValuesForKeys:就是你想要的。

NSDictionary *guestFoodChoice = [partyGuest dictionaryWithValuesForKeys:[NSArray arrayWithObject:@"favouriteMeal"]];

Answer 2

See enumerateKeysAndObjectsUsingBlock:.

Answer 3

NSDictionary *guestFoodChoice = [NSDictionary dictionaryWithObjectsAndKeys:[partyGuest itemForKey:@"favouriteMeal"],@"favouriteMeal",nil];