swift語言點評十九-類型轉化與檢查
1、oc比較：
-(BOOL) isKindOfClass: classObj判斷是否是這個類或者這個類的子類的實例
-(BOOL) isMemberOfClass: classObj 判斷是否是這個類的實例
2、is 類型檢查
Use the type check operator (is) to check whether an instance is of a certain subclass type.
3、 (as? or as!) 類型轉化
Use the conditional form of the type cast operator (as?) when you are not sure if the downcast will succeed.
Use the forced form of the type cast operator (as!) only when you are sure that the downcast will always succeed.
確信與不確信轉化。
4、Type Casting for Any and AnyObject
Swift provides two special types for working with nonspecific types:
-
Anycan represent an instance of any type at all, including function types. -
AnyObjectcan represent an instance of any class type.
To discover the specific type of a constant or variable that is known only to be of type Any or AnyObject, you can use an is or as pattern in a switch statement’s cases. The
The Any type represents values of any type, including optional types. Swift gives you a warning if you use an optional value where a value of type Any
Anyvalue, you can use the as operator to explicitly cast the optional to Any, as shown below.
let optionalNumber: Int? = 3things.append(optionalNumber) // Warningthings.append(optionalNumber as Any) // No warning
swift語言點評十九-類型轉化與檢查