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class Genre {
var name: String
init(name: String) { self.name = name }
}
class Classical : Genre {
}
class Pop : Genre {
}
var collection = [
Pop(name: "Hard Day's Night"),
Classical(name: "Canon in D"),
]
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The type of collection is inferred to be Genre
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Use is to check instance of.
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for song in collection {
if song is Classical {
print("\(song.name) is classical!")
} else if song is Pop {
print("\(song.name) is poppy!")
}
}
/*
Hard Day's Night is poppy!
Canon in D is classical!
*/
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# Downcasting
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as? returns an optional (if you aren't sure the cast will succeed)
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as throws a runtime error if the cast doesn't succeed
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for song in collection {
if let popSong = song as? Pop {
print("pop song")
} else if let classicalSong = song as? Classical {
print("classical song")
}
}
/*
pop song
classical song
*/
|
# AnyObject
|
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Tons of Cocoa APIs (dicts, arrays, etc.) return AnyObject, a generic
|
|
object wrapper. You have to use as to cast an AnyObject back to the
|
|
|
type you expect.
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AnyObject doesn't allow primitives--only class-based objects.
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var randomCollection: [AnyObject] = [
Pop(name: "Bishop Allen"),
Classical(name: "Bach"),
]
for item in randomCollection {
let songGenre = item as! Genre
print("\(songGenre.self)") // C11lldb_expr_03Pop (has 1 child) // C11lldb_expr_09Classical
print("\(songGenre.name)")
}
|
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Every item can also be downcasted in the for-loop
|
for item in randomCollection as! [Genre] {
print("\(item.name)")
}
/*
Bishop Allen
Bach
*/
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# Any
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Any allows primitives and class-based objects.
|
var groups = [Any]()
groups.append(1.0)
groups.append(1)
groups.append("string")
groups.append(Pop(name: "Long Winters"))
for item in groups {
switch item {
case let anInt as Int:
print("\(item) is an int")
case let aDouble as Double:
print("\(item) is a double")
case let aString as String:
print("\(item) is a string")
case let aGenre as Genre:
print("\(item) is a Genre")
default:
print("dunno")
}
}
/*
1.0 is a double
1 is an int
string is a string
C11lldb_expr_13Pop (has 1 child) is a Genre
*/
|