当范围是变量时，ruby数组子范围

Question

是否可以在ruby中将子范围应用于数组：

 > array = [4, 3, 2, 1]
 > array[0...2]
=> [4, 3]

如果[0...2]存储在变量中？我似乎无法获得一种语法来给我我想要的东西。如果有的话，取代以下<?>的是什么？

 > array = [4, 3, 2, 1]
 > range = [0...2]
 > array<?>
=> [4, 3]

Answer 1

是的，当然！这样做：

array = [4, 3, 2, 1]
exclusive_range = [0...2] # Will get 0th and 1st element of the array
inclusive_range = [0..2] # Will get 0th, 1st and 2nd element of the array
array[exclusive_range.first]
# => [4, 3]
array[inclusive_range.first] 
# => [4, 3, 2]

如果您想避免.first调用，可以将范围放在变量中（不在数组中）：

range = 0...2
array[range]
# => [4, 3]

Answer 2

请注意(0..2).size #=> 3。如果您想要返回[4,3]，则需要：

range = 0..1

您可以像这样使用它：

array[range]           #=> [4, 3]

或者像这样：

array.values_at *range #=> [4, 3]