Ios Swift类指针为?班级协议?
我有一门课,我们叫它什么课吧。SomeClass的实例具有指向SomeOtherClass的可选指针。通过这种方式,可以实例化SomeClass的实例,给定指向SomeOtherClass(或SomeOtherClass的子类)的指针,然后可以使用该指针动态创建属于SomeClass的SomeOtherClass的实例。EgIos Swift类指针为?班级协议?,ios,swift,class,casting,protocols,Ios,Swift,Class,Casting,Protocols,我有一门课,我们叫它什么课吧。SomeClass的实例具有指向SomeOtherClass的可选指针。通过这种方式,可以实例化SomeClass的实例,给定指向SomeOtherClass(或SomeOtherClass的子类)的指针,然后可以使用该指针动态创建属于SomeClass的SomeOtherClass的实例。Eg class SomeClass { var classPointer: SomeOtherClass.Type? } class SomeOtherClass {
class SomeClass {
var classPointer: SomeOtherClass.Type?
}
class SomeOtherClass {
}
到目前为止还不错。现在,我有一个协议——我们称之为SomeProtocol——我希望其他类遵守它。此协议中包含类函数:
protocol SomeProtocol {
static func someClassFunction()
}
extension SomeOtherClass : SomeProtocol {
class func someClassFunction() {
print("I am a class function being executed on SomeOtherClass")
}
}
正如预期的那样,我可以在其他类上调用此协议类函数,如下所示:
SomeOtherClass.someClassFunction() // Prints "I am a class function being executed on SomeOtherClass"
这是麻烦的部分。我想动态地确定SomeClass类指针的实例是否符合SomeProtocol,如果符合,则对其执行class函数。因此,我尝试使用as?:
// Create an instance of SomeClass and set it's classPointer to the SomeOtherClass class
let someInstance = SomeClass()
someInstance.classPointer = SomeOtherClass.self
// Check if the instance's classPointer class conforms to the SomeProtocol protocol
if let conformingClass = someInstance.classPointer as? SomeProtocol {
// If so, execute the class function in SomeProtocol on the instance's classPointer
conformingClass.someClassFunction() // Build fails "Static member someClassFunction cannot be used on instance of type SomeProtocol"
}
构建失败,错误为“someClassFunction的静态成员不能用于SomeProtocol类型的实例”
有没有办法完成我正在尝试的事情?目前,如果这不起作用,我只能想到这些替代方案(没有一个更可取,而且它们都相当粗糙):
-亚当啊哈!像往常一样,我一发布SO帖子,就会找出答案 对于那些想知道的人,您必须将类指针强制转换为协议的类型,而不是协议本身。该行:
if let conformingClass = someInstance.classPointer as? SomeProtocol {
需要更改为:
if let conformingClass = someInstance.classPointer as? SomeProtocol.Type {
然后,您将能够使用SomeProtocol中声明的类函数向conformingClass发送消息。完整的工作代码为:
class SomeClass {
var classPointer: SomeOtherClass.Type?
}
class SomeOtherClass {
}
protocol SomeProtocol {
static func someClassFunction()
}
extension SomeOtherClass : SomeProtocol {
class func someClassFunction() {
print("I am a class function being executed on SomeOtherClass")
}
}
// Create an instance of SomeClass and set it's classPointer to the SomeOtherClass class
let someInstance = SomeClass()
someInstance.classPointer = SomeOtherClass.self
// Check if the instance's classPointer class conforms to the SomeProtocol protocol
if let conformingClass = someInstance.classPointer as? SomeProtocol.Type {
// If so, execute the class function in SomeProtocol on the instance's classPointer
conformingClass.someClassFunction()
}
它是有效的:)
class SomeClass {
var classPointer: SomeOtherClass.Type?
}
class SomeOtherClass {
}
protocol SomeProtocol {
static func someClassFunction()
}
extension SomeOtherClass : SomeProtocol {
class func someClassFunction() {
print("I am a class function being executed on SomeOtherClass")
}
}
// Create an instance of SomeClass and set it's classPointer to the SomeOtherClass class
let someInstance = SomeClass()
someInstance.classPointer = SomeOtherClass.self
// Check if the instance's classPointer class conforms to the SomeProtocol protocol
if let conformingClass = someInstance.classPointer as? SomeProtocol.Type {
// If so, execute the class function in SomeProtocol on the instance's classPointer
conformingClass.someClassFunction()
}