Swift 1.2 / XCode 6.4
我有以下代码:
public protocol MapShape : AnyObject
{
func isEqualTo(other : MapShape) -> Bool
}
我尝试遵循该协议的通用类
public class MapMulti<T:MapShape>
{
let items : [T]
init(items : [T])
{
self.items = items
}
}
extension MapMulti : Equatable {}
public func ==<T:MapShape>(lhs: MapMulti<T>, rhs: MapMulti<T>) -> Bool
{
return true //simplify code
}
extension MapMulti : MapShape {
public func isEqualTo(other: MapShape) -> Bool {
if (object_getClassName(other) == object_getClassName(self))
{
return self == other as! MapMulti
}
return false
}
}
当我尝试使用以下内容进行构建失败时:
0 swift 0x000000010a3da2b8 llvm::sys::PrintStackTrace(__sFILE*) + 40
1 swift 0x000000010a3da794 SignalHandler(int) + 452
2 libsystem_platform.dylib 0x00007fff95704f1a _sigtramp + 26
3 libsystem_platform.dylib 0x00007fff55f3c832 _sigtramp + 3229841714
4 swift 0x0000000109d0112b swift::irgen::emitCategoryData(swift::irgen::IRGenModule&, swift::ExtensionDecl*) + 1819
5 swift 0x0000000109d09432 swift::irgen::IRGenModule::emitExtension(swift::ExtensionDecl*) + 514
6 swift 0x0000000109d061a4 swift::irgen::IRGenModule::emitSourceFile(swift::SourceFile&, unsigned int) + 100
7 swift 0x0000000109d87c77 performIRGeneration(swift::IRGenOptions&, swift::Module*, swift::SILModule*, llvm::StringRef, llvm::LLVMContext&, swift::SourceFile*, unsigned int) + 2151
8 swift 0x0000000109d88693 swift::performIRGeneration(swift::IRGenOptions&, swift::SourceFile&, swift::SILModule*, llvm::StringRef, llvm::LLVMContext&, unsigned int) + 51
9 swift 0x0000000109cc4087 frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 6647
10 swift 0x0000000109cc24e6 main + 1814
11 libdyld.dylib 0x00007fff998e75c9 start + 1
12 libdyld.dylib 0x0000000000000069 start + 1718717089
Stack dump:
1. While emitting IR for source file /<PROJECT>/MyProject/MapMulti.swift
导致失败的部分是尝试符合MapShape协议的扩展,如果我评论它编译它。
此外,我认为我的泛型理解中的某些内容是错误的。当我尝试这个时:
let multipoint : MapMulti<MapShape> = MapMulti<MapPoint>(items: [P1,P2,P3])
它表示 MapMulti(MapPoint)无法转换为MapMulti(MapShape)
即使MapPoint符合MapShape,我也可以这样做:
let shape : MapShape = MapPoint()
相反,我必须这样做:我不喜欢。
let multiShape : MapMulti<MapShape> = MapMulti<MapShape>(items: [P1,P2,P3])
请,需要帮助!!!
编辑:添加了MapPoint实施
public class MapPoint : MapShape{
let lat : Double
let long : Double
init (lat : Double, long : Double)
{
self.lat = lat
self.long = long
}
}
extension MapPoint : Equatable{}
public func ==(lhs: MapPoint, rhs: MapPoint) -> Bool
{
return lhs.long == rhs.long && lhs.lat == rhs.lat
}
extension MapPoint : MapShape
{
public func isEqualTo(other: MapShape) -> Bool {
if (object_getClassName(other) == object_getClassName(self))
{
return self == other as! MapPoint
}
return false
}
}
答案 0 :(得分:7)
我对您的代码做了一些小改动,现在就编译了
public protocol MapShape // Removed the : AnyObject
{
func isEqualTo(other : MapShape) -> Bool
}
public class MapMulti<T:MapShape>
{
let items : [T]
init(items : [T])
{
self.items = items
}
}
extension MapMulti : Equatable {}
public func ==<T:MapShape>(lhs: MapMulti<T>, rhs: MapMulti<T>) -> Bool
{
return true //simplify code
}
现在,如果您只是想知道两个元素是否是同一个类的实例,那么下一个更改就会起作用:
extension MapMulti : MapShape {
public func isEqualTo(other: MapShape) -> Bool {
// You can compare against dynamic class here
return self.dynamicType == other.dynamicType
}
}
在这个已回答的问题中有一个非常好的解释和dynamicType示例:Identifying a subclass with Swift Generics works with custom class but not with UITapGestureRecognizer
我希望它有所帮助