Question

如果我有一个带有多个字典对象的NSArray（或可变数组）（每个字典都是Person），就像这样：

[
  { forename: chris, surname: smith, age: 22 }
  { forename: paul, surname: smith, age: 24 }
  { forename: dave, surname: jones, age: 21 }
  { forename: alan, surname: jones, age: 26 }
  { forename: cecil, surname: reeves, age: 32 }
  { forename: pablo, surname: sanchez, age: 42 }
]

我如何将它分成四个数组的数组，按姓氏（并在该名字中）排序，如下所示：

[
    [ 
      { forename: alan, surname: jones, age: 26 }
      { forename: dave, surname: jones, age: 21 }
    ]
    [  
      { forename: cecil, surname: reeves, age: 32 }
    ]
    [
      { forename: pablo, surname: sanchez, age: 42 }
    ]
    [ 
      { forename: chris, surname: smith, age: 22 }
      { forename: paul, surname: smith, age: 24 }
    ]
]

Answer 1

你可以使用键值编码和谓词来做一些非常整洁的东西......

//retrieve an array of the distinct surnames
NSArray * distinctSurnames = [peopleArray valueForKeyPath:@"@distinctUnionOfObjects.surname"];
//at this point, if you need the surnames in a specific order, you can do so here.

NSMutableArray * groupedPeople = [NSMutableArray array];

//for each of the surnames...
for (NSString * surname in distinctSurnames) {
  //create a predicate to only find people with this surname
  NSPredicate * filter = [NSPredicate predicateWithFormat:@"surname = %@", surname];
  //retrieve only the people with this surname and add them to the final array
  [groupedPeople addObject:[peopleArray filteredArrayUsingPredicate:filter]];
}

这适用于Person对象（可能更好）或字典，只要字典有@"surname"键或Person对象有{{1方法。

Answer 2

您应该使用专门的Person类，而不是NSDictionary。

您可以先将其分组到词典数组字典中，例如

NSMutableDictionary* result = [NSMutableDictionary dictionary];
for (Person* person in peopleArray) {
    NSString* surname = person.surname;
    NSMutableArray* surnameArray = [result objectForKey:surname];
    if (surnameArray == nil) {
        [result setObject:[NSMutableArray arrayWithObject:person]
                   forKey:surname]; 
    } else {
        [surnameArray addObject:person];
    }
}
return result;

如果你真的需要一个数组，你可以使用[result allValues]。

如果您需要排序数组，则需要手动对其进行排序：

NSArray* sortedSurnames = [[result allKeys] sortedArrayUsingSelector:@selector(compare:)];
return [result objectsForKeys:sortedSurnames notFoundMarker:[NSNull null]];

如何将NSDrray的NSArray转变为NSDictionarys的嵌套NSArray

2 个答案: