问题描述
假设我有一个对象，其类型类似于NullableArray{Int64}-我怎么知道元素的类型为Int64(好吧，Nullable{Int64})却没有实际访问任何元素(即，可以在以下情况下完成此操作)该对象为空).有没有一种通用的方法可以从类型Type{SubType}的对象中找出SubType是什么?
Suppose I have an object which has a type like NullableArray{Int64} -- how do I know that the elements have type Int64 (well, Nullable{Int64}) without actually accessing any element (ie, it can be done when the object is empty). Is there a general way to figure out what SubType is from an object of type Type{SubType}?
糟糕，为了进一步扩展下面的公认答案，我意识到我正在做eltype(x)，但对于Nullables的示例，需要做eltype(eltype(x)).
Whoops, to expand on the accepted answer below I realized I was doing eltype(x) but needed to do eltype(eltype(x)) for the example of Nullables.
推荐答案
，您可以使用 eltype
you can use eltype
assert(eltype(collect(1:3)) == Int)
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