是否有一种方法可以在swift中打印变量的运行时类型?例如:
var now = NSDate()
var soon = now.dateByAddingTimeInterval(5.0)
println("\(now.dynamicType)")
// Prints "(Metatype)"
println("\(now.dynamicType.description()")
// Prints "__NSDate" since objective-c Class objects have a "description" selector
println("\(soon.dynamicType.description()")
// Compile-time error since ImplicitlyUnwrappedOptional<NSDate> has no "description" method
在上面的例子中，我正在寻找一种方法来显示变量“soon”的类型是ImplicitlyUnwrappedOptional<NSDate>，或至少NSDate!
当前回答
Swift 3.0, Xcode 8
使用下面的代码，您可以向实例请求其类。你也可以比较两个实例，是否具有相同的类。
// CREATE pure SWIFT class
class MySwiftClass {
var someString : String = "default"
var someInt : Int = 5
}
// CREATE instances
let firstInstance = MySwiftClass()
let secondInstance = MySwiftClass()
secondInstance.someString = "Donald"
secondInstance.someInt = 24
// INSPECT instances
if type(of: firstInstance) === MySwiftClass.self {
print("SUCCESS with ===")
} else {
print("PROBLEM with ===")
}
if type(of: firstInstance) == MySwiftClass.self {
print("SUCCESS with ==")
} else {
print("PROBLEM with ==")
}
// COMPARE CLASS OF TWO INSTANCES
if type(of: firstInstance) === type(of: secondInstance) {
print("instances have equal class")
} else {
print("instances have NOT equal class")
}
其他回答
在Swift 3.0中，你可以使用type(of:)，因为dynamicType关键字已被删除。
斯威夫特3.0
let string = "Hello"
let stringArray = ["one", "two"]
let dictionary = ["key": 2]
print(type(of: string)) // "String"
// Get type name as a string
String(describing: type(of: string)) // "String"
String(describing: type(of: stringArray)) // "Array<String>"
String(describing: type(of: dictionary)) // "Dictionary<String, Int>"
// Get full type as a string
String(reflecting: type(of: string)) // "Swift.String"
String(reflecting: type(of: stringArray)) // "Swift.Array<Swift.String>"
String(reflecting: type(of: dictionary)) // "Swift.Dictionary<Swift.String, Swift.Int>"
Swift 3.0, Xcode 8
使用下面的代码，您可以向实例请求其类。你也可以比较两个实例，是否具有相同的类。
// CREATE pure SWIFT class
class MySwiftClass {
var someString : String = "default"
var someInt : Int = 5
}
// CREATE instances
let firstInstance = MySwiftClass()
let secondInstance = MySwiftClass()
secondInstance.someString = "Donald"
secondInstance.someInt = 24
// INSPECT instances
if type(of: firstInstance) === MySwiftClass.self {
print("SUCCESS with ===")
} else {
print("PROBLEM with ===")
}
if type(of: firstInstance) == MySwiftClass.self {
print("SUCCESS with ==")
} else {
print("PROBLEM with ==")
}
// COMPARE CLASS OF TWO INSTANCES
if type(of: firstInstance) === type(of: secondInstance) {
print("instances have equal class")
} else {
print("instances have NOT equal class")
}
Xcode 7.3.1, Swift 2.2:
字符串(instanceToPrint.self) .componentsSeparatedByString .last(“。”)
我目前的Xcode版本是6.0 (6A280e)。
import Foundation
class Person { var name: String; init(name: String) { self.name = name }}
class Patient: Person {}
class Doctor: Person {}
var variables:[Any] = [
5,
7.5,
true,
"maple",
Person(name:"Sarah"),
Patient(name:"Pat"),
Doctor(name:"Sandy")
]
for variable in variables {
let typeLongName = _stdlib_getDemangledTypeName(variable)
let tokens = split(typeLongName, { $0 == "." })
if let typeName = tokens.last {
println("Variable \(variable) is of Type \(typeName).")
}
}
输出:
Variable 5 is of Type Int.
Variable 7.5 is of Type Double.
Variable true is of Type Bool.
Variable maple is of Type String.
Variable Swift001.Person is of Type Person.
Variable Swift001.Patient is of Type Patient.
Variable Swift001.Doctor is of Type Doctor.
