列出一個類的所有子類

Question

我可以返回一個類的所有子類的列表嗎？例如：

class Mother { 

} 

class ChildFoo: Mother { 

} 

class ChildBar: Mother { 

} 

let motherSubclasses = ... // TODO 
print(motherSubclasses) // should to return [ChildFoo.self, ChildBar.self] 

Answer 1

令人驚訝的是Objective-C的運行時函數只是工作以及與斯威夫特班，即使他們不從NSObject子類。此外，Swift中的所有類似於從SwiftObject派生。 SwiftObject本身沒有超類。

首先，包裝結構來處理ObjC運行系統功能：

import Foundation 

struct ClassInfo : CustomStringConvertible, Equatable { 
    let classObject: AnyClass 
    let className: String 

    init?(_ classObject: AnyClass?) { 
     guard classObject != nil else { return nil } 

     self.classObject = classObject! 

     let cName = class_getName(classObject)! 
     self.className = String(cString: cName) 
    } 

    var superclassInfo: ClassInfo? { 
     let superclassObject: AnyClass? = class_getSuperclass(self.classObject) 
     return ClassInfo(superclassObject) 
    } 

    var description: String { 
     return self.className 
    } 

    static func ==(lhs: ClassInfo, rhs: ClassInfo) -> Bool { 
     return lhs.className == rhs.className 
    } 
} 

這裏是你如何使用它：

class Mother { } 
class ChildFoo: Mother { } 
class ChildBar: Mother { } 

class AnIrrelevantClass { } 

let motherClassInfo = ClassInfo(Mother.self)! 
var subclassList = [ClassInfo]() 

var count = UInt32(0) 
let classList = objc_copyClassList(&count)! 

for i in 0..<Int(count) { 
    if let classInfo = ClassInfo(classList[i]), 
     let superclassInfo = classInfo.superclassInfo, 
     superclassInfo == motherClassInfo 
    { 
     subclassList.append(classInfo) 
    } 
} 

print(subclassList) 

這隻能執行淺層搜索，所以它不會打掃孫子班，但你明白了。