我是Swift新手,目前正在使用子类化。我试图实现的是简单地通过继承存储的属性到现有的类,然后将现有的实例从类中复制到子类中。 我与MPMediaEntity想这一点,并子类这样说:Swift - 将MPMediaEntity实例复制到子类中
class MPMediaEntityWithMyString: MPMediaEntity{
var myString:String = ""
}
然后拿到MPMediaEntities列表我简单地做:
// Get all the songs in an array
let mediaItems = MPMediaQuery.songsQuery().items
// Go through each song, make a copy of it as MPMediaEntityWithMyString
// and modify the myString property
for song in mediaItems{
// This is where I stall. How do I copy the MPMediaEntity into the MPMediaEntityWithMyString? It moans about it not being convertible
var songCopy:MPMediaEntityWithMyString = song
songCopy.myString = "testing!"
println(songCopy.myString)
}
我在做什么这显然是错误的?