我如何最容易找到一个三维数组在Cocoa？ [英] How can I most easily flatten a three-dimensional array in Cocoa?

问题描述

说我有一个这样的数组：

  NSArray * threeDimensionalArray = @ [
 @ [
 @ [@Peter，@Paul，@Mary]，@ [@Joe，@Jane] 
]，
 @ [
 @ @Alice，@Bob] 
] 
]; 
  

，我希望它成为：

  @ [@Peter，@Paul，@Mary，@Joe，@Jane，@Alice，@Bob] $ b $我如何最容易地创建这个扁平数组？
 
 >解决方案
键值编码（KVC）集合运算符 @unionOfArrays 使一级数组平坦化，因此应用它两次产生所需的结果。
 
 
 
集合运算符（ @count 除外）需要一个集合属性的关键路径，已经是数组（因此集合）本身，关键路径必须 self 。 
 
 
 
因此，我们需要将 @unionOfArrays 应用两次 self 键路径，产生以下KVC调用以展平3D数组：
  NSArray * flattenedArray = [threeDimensionalArray valueForKeyPath：@ @ unionOfArrays.self。@ unionOfArrays.self]; 
  
 
Say I have an array such as this:
NSArray *threeDimensionalArray = @[
 @[     
     @[ @"Peter", @"Paul", @"Mary" ], @[ @"Joe", @"Jane" ]
  ],
 @[
     @[ @"Alice", @"Bob" ]
  ]
];
and I want it to become:
@[ @"Peter", @"Paul", @"Mary", @"Joe", @"Jane", @"Alice", @"Bob" ]
How can I most easily create this flattened array?
解决方案
The key-value coding (KVC) collection operator @unionOfArrays flattens one level of arrays, so applying it twice produces the desired result.

Collection operators (other than @count) need a key path to a collection property, and since our objects are already arrays (and hence collections) in themselves, the key path will have to be self. 

We therefore need to  apply @unionOfArrays twice with the self key path, yielding the following KVC call to flatten a 3D array:
NSArray *flattenedArray = [threeDimensionalArray valueForKeyPath: @"@[e-mail]"];


                        
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