在 Swift 中，空数组文字是否分配零容量用于存储？

Question

let arr: [Int] = []

在这个实例中，Swift 是否没有分配任何缓冲区，因为数组文字是空的？

Answer 1

查看标准库的源代码，我们可以找到一个类，名为

__EmptyArrayStorage

。

/// Class used whose sole instance is used as storage for empty
/// arrays.  The instance is defined in the runtime and statically
/// initialized.  See stdlib/runtime/GlobalObjects.cpp for details.
/// Because it's statically referenced, it requires non-lazy realization
/// by the Objective-C runtime.
///
/// NOTE: older runtimes called this _EmptyArrayStorage. The two must
/// coexist, so it was renamed. The old name must not be used in the new
/// runtime.
@_fixed_layout
@usableFromInline
@_objc_non_lazy_realization
internal final class __EmptyArrayStorage
  : __ContiguousArrayStorageBase {

因此仍然分配了一部分堆来存储

__EmptyArrayStorage

的这个实例，但所有空 Swift 数组将共享相同的存储空间。