Any decoupling approach has at least one disadvantage: What if the client code needs specific functionality provided by only one of the implementations?
任何去耦方法都至少有一个缺点：如果客户机代码仅需要一个实现所提供的特定功能，怎么办？
2
There is also at least one disadvantage of Scala’s constraints on constructors.
不过，这样也有至少一个缺点。
3
More recently, researchers have been looking at how family size might affect social skills -- with some evidence that onlies are at a disadvantage, at least early on.