您不能拥有类型为Adjustable的项目数组，因为Adjustable并不是真正的类型.这是一张蓝图，描述了一组类型，每个T的可能值中的一个.

You can't have an array of items of type Adjustable, because Adjustable isn't really a type. It's a blue print that describes a set of types, one per every possible value of T.

要解决此问题，您需要使用类型橡皮擦 https://medium.com/dunnhumby-data-science-engineering/swift-associated-type-design-patterns-6c56c5b0a73a

To get around this, you need to use a type eraser https://medium.com/dunnhumby-data-science-engineering/swift-associated-type-design-patterns-6c56c5b0a73a