正如标题所说，我正在尝试通过+=运算符将文本附加到隐式解包的可选字符串，这给了我'String!'isnotidenticalto'UInt8'让你明白我的意思:varmyString:String="Hello"myString+="world"//worksgreatvarmyOptionalString:String!="Foo"myOptionalString+="bar"//error:String!isnotidenticalto'UInt8'但是，如果我在作业有效时附加它varmyOptionalString:String!="Foo"myOptionalString=m