您可以简单地执行以下操作：

// this doesn't compile,but SomeClass is a class and it should work
class ClassA<T> where T: SomeClass
{
    // here,you get the classic:
    // Only non-nullable value type could be underlying of 'System.Nullable'
    // What this makes clear is that the compiler doesn't understand that
    // T is strictly a reference Type now
    public GenericType<T?> DoSomething()
    {
        thrown new NotImplementedException();
    }
}

您可以使用.filter进行此操作：

var reservedWords = ["var","if","for","switch","int","class"]
var varNames = ["if","var","identifier","thisIsAnIdentifier","b13","a","i","number_1","class"]

let newArray = varNames.filter {!reservedWords.contains($0)}

这是输出：

另一种方法是you use Sets，特别是Set.subtract（修改列表）或Set.subtracting（创建新列表）。由于集合是唯一的，因此它应该表现更好。

let employees: Set = ["Alicia","Bethany","Chris","Diana","Eric"]
let neighbors = ["Bethany","Eric","Forlani","Greta"]
let nonNeighbors = employees.subtracting(neighbors)
print(nonNeighbors)

  

“ [[” Chris“，” Diana“，” Alicia“]”