Is there a way to print the runtime type of a variable in swift? For example:
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
In the example above, I'm looking for a way to show that the variable "soon" is of type ImplicitlyUnwrappedOptional<NSDate>, or at least NSDate!.
Update September 2016
Swift 3.0: Use type(of:), e.g. type(of: someThing) (since the dynamicType keyword has been removed)
Update October 2015:
I updated the examples below to the new Swift 2.0 syntax (e.g. println was replaced with print, toString() is now String()).
From the Xcode 6.3 release notes:
#nschum points out in the comments that the Xcode 6.3 release notes show another way:
Type values now print as the full demangled type name when used with
println or string interpolation.
import Foundation
class PureSwiftClass { }
var myvar0 = NSString() // Objective-C class
var myvar1 = PureSwiftClass()
var myvar2 = 42
var myvar3 = "Hans"
print( "String(myvar0.dynamicType) -> \(myvar0.dynamicType)")
print( "String(myvar1.dynamicType) -> \(myvar1.dynamicType)")
print( "String(myvar2.dynamicType) -> \(myvar2.dynamicType)")
print( "String(myvar3.dynamicType) -> \(myvar3.dynamicType)")
print( "String(Int.self) -> \(Int.self)")
print( "String((Int?).self -> \((Int?).self)")
print( "String(NSString.self) -> \(NSString.self)")
print( "String(Array<String>.self) -> \(Array<String>.self)")
Which outputs:
String(myvar0.dynamicType) -> __NSCFConstantString
String(myvar1.dynamicType) -> PureSwiftClass
String(myvar2.dynamicType) -> Int
String(myvar3.dynamicType) -> String
String(Int.self) -> Int
String((Int?).self -> Optional<Int>
String(NSString.self) -> NSString
String(Array<String>.self) -> Array<String>
Update for Xcode 6.3:
You can use the _stdlib_getDemangledTypeName():
print( "TypeName0 = \(_stdlib_getDemangledTypeName(myvar0))")
print( "TypeName1 = \(_stdlib_getDemangledTypeName(myvar1))")
print( "TypeName2 = \(_stdlib_getDemangledTypeName(myvar2))")
print( "TypeName3 = \(_stdlib_getDemangledTypeName(myvar3))")
and get this as output:
TypeName0 = NSString
TypeName1 = __lldb_expr_26.PureSwiftClass
TypeName2 = Swift.Int
TypeName3 = Swift.String
Original answer:
Prior to Xcode 6.3 _stdlib_getTypeName got the mangled type name of a variable. Ewan Swick's blog entry helps to decipher these strings:
e.g. _TtSi stands for Swift's internal Int type.
Mike Ash has a great blog entry covering the same topic.
Edit: A new toString function has been introduced in Swift 1.2 (Xcode 6.3).
You can now print the demangled type of any type using .self and any instance using .dynamicType:
struct Box<T> {}
toString("foo".dynamicType) // Swift.String
toString([1, 23, 456].dynamicType) // Swift.Array<Swift.Int>
toString((7 as NSNumber).dynamicType) // __NSCFNumber
toString((Bool?).self) // Swift.Optional<Swift.Bool>
toString(Box<SinkOf<Character>>.self) // __lldb_expr_1.Box<Swift.SinkOf<Swift.Character>>
toString(NSStream.self) // NSStream
Try calling YourClass.self and yourObject.dynamicType.
Reference: https://devforums.apple.com/thread/227425.
Swift 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>"
Is this what you're looking for?
println("\(object_getClassName(now))");
It prints "__NSDate"
UPDATE: Please note this no longer seems to work as of Beta05
My current Xcode is Version 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).")
}
}
Output:
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.
As of Xcode 6.3 with Swift 1.2, you can simply convert type values into the full demangled String.
toString(Int) // "Swift.Int"
toString(Int.Type) // "Swift.Int.Type"
toString((10).dynamicType) // "Swift.Int"
println(Bool.self) // "Swift.Bool"
println([UTF8].self) // "Swift.Array<Swift.UTF8>"
println((Int, String).self) // "(Swift.Int, Swift.String)"
println((String?()).dynamicType)// "Swift.Optional<Swift.String>"
println(NSDate) // "NSDate"
println(NSDate.Type) // "NSDate.Type"
println(WKWebView) // "WKWebView"
toString(MyClass) // "[Module Name].MyClass"
toString(MyClass().dynamicType) // "[Module Name].MyClass"
You can still access the class, through className (which returns a String).
There are actually several ways to get the class, for example classForArchiver, classForCoder, classForKeyedArchiver (all return AnyClass!).
You can't get the type of a primitive (a primitive is not a class).
Example:
var ivar = [:]
ivar.className // __NSDictionaryI
var i = 1
i.className // error: 'Int' does not have a member named 'className'
If you want to get the type of a primitive, you have to use bridgeToObjectiveC(). Example:
var i = 1
i.bridgeToObjectiveC().className // __NSCFNumber
You can use reflect to get information about object.
For example name of object class:
var classname = reflect(now).summary
Xcode 8 Swift 3.0 use type(of:)
let className = "\(type(of: instance))"
I had luck with:
let className = NSStringFromClass(obj.dynamicType)
SWIFT 5
With the latest release of Swift 3 we can get pretty descriptions of type names through the String initializer. Like, for example print(String(describing: type(of: object))). Where object can be an instance variable like array, a dictionary, an Int, a NSDate, an instance of a custom class, etc.
Here is my complete answer: Get class name of object as string in Swift
That question is looking for a way to getting the class name of an object as string but, also i proposed another way to getting the class name of a variable that isn't subclass of NSObject. Here it is:
class Utility{
class func classNameAsString(obj: Any) -> String {
//prints more readable results for dictionaries, arrays, Int, etc
return String(describing: type(of: obj))
}
}
I made a static function which takes as parameter an object of type Any and returns its class name as String :) .
I tested this function with some variables like:
let diccionary: [String: CGFloat] = [:]
let array: [Int] = []
let numInt = 9
let numFloat: CGFloat = 3.0
let numDouble: Double = 1.0
let classOne = ClassOne()
let classTwo: ClassTwo? = ClassTwo()
let now = NSDate()
let lbl = UILabel()
and the output was:
diccionary is of type Dictionary
array is of type Array
numInt is of type Int
numFloat is of type CGFloat
numDouble is of type Double
classOne is of type: ClassOne
classTwo is of type: ClassTwo
now is of type: Date
lbl is of type: UILabel
In Xcode 8, Swift 3.0
Steps:
1. Get the Type:
Option 1:
let type : Type = MyClass.self //Determines Type from Class
Option 2:
let type : Type = type(of:self) //Determines Type from self
2. Convert Type to String:
let string : String = "\(type)" //String
In Swift 3.0, you can use type(of:), as dynamicType keyword has been removed.
To get a type of object or class of object in Swift, you must need to use a type(of: yourObject)
type(of: yourObject)
When using Cocoa (not CocoaTouch), you can use the className property for objects that are subclasses of NSObject.
println(now.className)
This property is not available for normal Swift objects, which aren't subclasses of NSObject (and in fact, there is no root id or object type in Swift).
class Person {
var name: String?
}
var p = Person()
println(person.className) // <- Compiler error
In CocoaTouch, at this time there is not a way to get a string description of the type of a given variable. Similar functionality also does not exist for primitive types in either Cocoa or CocoaTouch.
The Swift REPL is able to print out a summary of values including its type, so it is possible this manner of introspection will be possible via an API in the future.
EDIT: dump(object) seems to do the trick.
The top answer doesn't have a working example of the new way of doing this using type(of:. So to help rookies like me, here is a working example, taken mostly from Apple's docs here - https://developer.apple.com/documentation/swift/2885064-type
doubleNum = 30.1
func printInfo(_ value: Any) {
let varType = type(of: value)
print("'\(value)' of type '\(varType)'")
}
printInfo(doubleNum)
//'30.1' of type 'Double'
I've tried some of the other answers here but milage seems to very on what the underling object is.
However I did found a way you can get the Object-C class name for an object by doing the following:
now?.superclass as AnyObject! //replace now with the object you are trying to get the class name for
Here is and example of how you would use it:
let now = NSDate()
println("what is this = \(now?.superclass as AnyObject!)")
In this case it will print NSDate in the console.
I found this solution which hopefully might work for someone else.
I created a class method to access the value. Please bear in mind this will work for NSObject subclass only. But at least is a clean and tidy solution.
class var className: String!{
let classString : String = NSStringFromClass(self.classForCoder())
return classString.componentsSeparatedByString(".").last;
}
In the latest XCode 6.3 with Swift 1.2, this is the only way I found:
if view.classForCoder.description() == "UISegment" {
...
}
Many of the answers here do not work with the latest Swift (Xcode 7.1.1 at time of writing).
The current way of getting the information is to create a Mirror and interrogate that. For the classname it is as simple as:
let mirror = Mirror(reflecting: instanceToInspect)
let classname:String = mirror.description
Additional information about the object can also be retrieved from the Mirror. See http://swiftdoc.org/v2.1/type/Mirror/ for details.
Swift version 4:
print("\(type(of: self)) ,\(#function)")
// within a function of a class
Thanks #Joshua Dance
In lldb as of beta 5, you can see the class of an object with the command:
fr v -d r shipDate
which outputs something like:
(DBSalesOrderShipDate_DBSalesOrderShipDate_ *) shipDate = 0x7f859940
The command expanded out means something like:
Frame Variable (print a frame variable) -d run_target (expand dynamic types)
Something useful to know is that using "Frame Variable" to output variable values guarantees no code is executed.
I've found a solution for self-developed classes (or such you have access to).
Place the following computed property within your objects class definition:
var className: String? {
return __FILE__.lastPathComponent.stringByDeletingPathExtension
}
Now you can simply call the class name on your object like so:
myObject.className
Please note that this will only work if your class definition is made within a file that is named exactly like the class you want the name of.
As this is commonly the case the above answer should do it for most cases. But in some special cases you might need to figure out a different solution.
If you need the class name within the class (file) itself you can simply use this line:
let className = __FILE__.lastPathComponent.stringByDeletingPathExtension
Maybe this method helps some people out there.
Based on the answers and comments given by Klass and Kevin Ballard above, I would go with:
println(_stdlib_getDemangledTypeName(now).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(soon).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(soon?).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(soon!).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar0).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar1).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar2).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar3).componentsSeparatedByString(".").last!)
which will print out:
"NSDate"
"ImplicitlyUnwrappedOptional"
"Optional"
"NSDate"
"NSString"
"PureSwiftClass"
"Int"
"Double"
let i: Int = 20
func getTypeName(v: Any) -> String {
let fullName = _stdlib_demangleName(_stdlib_getTypeName(i))
if let range = fullName.rangeOfString(".") {
return fullName.substringFromIndex(range.endIndex)
}
return fullName
}
println("Var type is \(getTypeName(i)) = \(i)")
Swift 4:
// "TypeName"
func stringType(of some: Any) -> String {
let string = (some is Any.Type) ? String(describing: some) : String(describing: type(of: some))
return string
}
// "ModuleName.TypeName"
func fullStringType(of some: Any) -> String {
let string = (some is Any.Type) ? String(reflecting: some) : String(reflecting: type(of: some))
return string
}
Usage:
print(stringType(of: SomeClass())) // "SomeClass"
print(stringType(of: SomeClass.self)) // "SomeClass"
print(stringType(of: String())) // "String"
print(fullStringType(of: String())) // "Swift.String"
There appears to be no generic way to print the type name of an arbitrary value's type. As others have noted, for class instances you can print value.className but for primitive values it appears that at runtime, the type information is gone.
For instance, it looks as if there's not a way to type: 1.something() and get out Int for any value of something. (You can, as another answer suggested, use i.bridgeToObjectiveC().className to give you a hint, but __NSCFNumber is not actually the type of i -- just what it will be converted to when it crosses the boundary of an Objective-C function call.)
I would be happy to be proven wrong, but it looks like the type checking is all done at compile time, and like C++ (with RTTI disabled) much of the type information is gone at runtime.
This is how you get a type string of your object or Type which is consistent and takes into account to which module the object definition belongs to or nested in. Works in Swift 4.x.
#inline(__always) func typeString(for _type: Any.Type) -> String {
return String(reflecting: type(of: _type))
}
#inline(__always) func typeString(for object: Any) -> String {
return String(reflecting: type(of: type(of: object)))
}
struct Lol {
struct Kek {}
}
// if you run this in playground the results will be something like
typeString(for: Lol.self) // __lldb_expr_74.Lol.Type
typeString(for: Lol()) // __lldb_expr_74.Lol.Type
typeString(for: Lol.Kek.self)// __lldb_expr_74.Lol.Kek.Type
typeString(for: Lol.Kek()) // __lldb_expr_74.Lol.Kek.Type
Not exactly what you are after, but you can also check the type of the variable against Swift types like so:
let object: AnyObject = 1
if object is Int {
}
else if object is String {
}
For example.
Xcode 7.3.1, Swift 2.2:
String(instanceToPrint.self).componentsSeparatedByString(".").last
Am I taking crazy pills? Directly out of the documentation:
“Swift automatically bridges between the String type and the NSString class. This means that anywhere you use an NSString object, you can use a Swift String type instead and gain the benefits of both types—the String type’s interpolation and Swift-designed APIs and the NSString class’s broad functionality. For this reason, you should almost never need to use the NSString class directly in your own code. In fact, when Swift imports Objective-C APIs, it replaces all of the NSString types with String types. When your Objective-C code uses a Swift class, the importer replaces all of the String types with NSString in imported API.
To enable string bridging, just import Foundation.”
I've done this... consider:
import Foundation
var str = "Hello World"
var range = str.rangeOfString("e")
// returns error: String does not contain member named: rangeOfString()
However:
var str = "Hello World" as NSString
var range = str.rangeOfString("e")
// returns correct (2, 1)
Am I missing something?
To go from String to NSString use the following constructor:
let swiftString:String = "I'm a string."
let objCString:NSString = NSString(string:swiftString)
With Xcode 7 (beta), using a downcast from String to NSString, as in below example, will result in a warning message, Cast from 'String?' to unrelated type 'NSString' always fails:
let objcString:NSString = swiftString as! NSString // results in error
You already have the answer in your question. You're missing the cast. When writing Swift code, a statement such as this one
var str = "Hello World"
creates a Swift String, not an NSString. To make it work as an NSString, you should cast it to an NSString using the as operator before using it.
This is different than calling a method written in Objective-C and supplying a String instead of an NSString as a parameter.
Here is example for this :
string str_simple = "HELLO WORLD";
//string to NSString
NSString *stringinObjC = [NSString stringWithCString:str_simple.c_str()
encoding:[NSString defaultCStringEncoding]];
NSLog(stringinObjC);
With an array: How do I do indexOfObject or a proper containsObject?
I mean I know I could just bridge the Array to NSArray and do it there ^^
But there must be a 'native' way of doing this
P.S. for the containsObject I guess I could filter the array too but for indexOf?
You can use the built-in find, and thus avoid bridging to Objective-C — but only if your element type is Equatable. (If it isn't Equatable, you can make it so with a comparison function and an extension.)
Example:
func == (lhs:Piece,rhs:Piece) -> Bool {
return lhs.val == rhs.val
}
class Piece:Equatable,Printable {
var val : Int
var description : String { return String(val) }
init (_ v:Int) {
val = v
}
}
Now you can call find(arr,p) where arr is an Array<Piece> and p is a Piece.
Once you have this, you can develop utilities based on it. For example, here's a global function to remove an object from an array without bridging to Objective-C:
func removeObject<T:Equatable>(inout arr:Array<T>, object:T) -> T? {
if let found = find(arr,object) {
return arr.removeAtIndex(found)
}
return nil
}
And test it like this:
var arr = [Piece(1), Piece(2), Piece(3)]
removeObject(&arr,Piece(2))
println(arr)
You can do this for NSObject subclasses too. Example:
func == (v1:UIView, v2:UIView) -> Bool {
return v1.isEqual(v2)
}
extension UIView : Equatable {}
Now you can call find on an Array of UIView. It's sort of a pain in the butt, though, having to do this for every single class where you want to be able to use find on an Array of that class. I have filed an enhancement request with Apple requesting that all NSObject subclasses be considered Equatable and that == should fall back on isEqual: automatically.
EDIT Starting in Seed 3, this is automatic for UIView and other NSObject classes. So find now just works for them.
EDIT 2 Starting in Swift 2.0, indexOf will exist as a method:
let s = ["Manny", "Moe", "Jack"]
let ix = s.indexOf("Moe") // 1
Alternatively, it takes a function that returns Bool:
let ix2 = s.indexOf {$0.hasPrefix("J")} // 2
Again, this works only on collections of Equatable, since obviously you cannot locate a needle in a haystack unless you have a way of identifying a needle when you come to it.
EDIT 3 Swift 2.0 also introduces protocol extensions. This means I can rewrite my global function removeObject as a method!
For example:
extension RangeReplaceableCollectionType where Generator.Element : Equatable {
mutating func removeObject(object:Self.Generator.Element) {
if let found = self.indexOf(object) {
self.removeAtIndex(found)
}
}
}
Since Array adopts RangeReplaceableCollectionType, now I can write code like this:
var arr = [Piece(1), Piece(2), Piece(3)]
arr.removeObject(Piece(2))
Oh, happy day!
Its actually able to be done in Swift. To get the index use find(YourArray, ObjectToFind)
As I was told, this isn't available yet / I have to bridge it to NSArray
I don't like this and it feels dirty so I went and did this in an extension. that way it hides the usage of NSArray and allows apple to provide it later
import Foundation
extension Array {
func contains(object:AnyObject!) -> Bool {
if(self.isEmpty) {
return false
}
let array: NSArray = self.bridgeToObjectiveC();
return array.containsObject(object)
}
func indexOf(object:AnyObject!) -> Int? {
var index = NSNotFound
if(!self.isEmpty) {
let array: NSArray = self.bridgeToObjectiveC();
index = array.indexOfObject(object)
}
if(index == NSNotFound) {
return Optional.None;
}
return index
}
//#pragma mark KVC
func getKeyPath(keyPath: String!) -> AnyObject! {
return self.bridgeToObjectiveC().valueForKeyPath(keyPath);
}
}
https://gist.github.com/Daij-Djan/9d1c4b1233b4017f3b67
Apple provide an example of exactly this in the The Swift Programming Language book. Specifically, see the section on Type Constraints in Action (p621 in the iBook).
func findIndex<T: Equatable>(array: [T], valueToFind: T) -> Int? {
for (index, value) in enumerate(array) {
if value == valueToFind {
return index
}
}
return nil
}
Everything depends upon your type implementing Equatable.
The Swift Programming Language covers that and explains how to implement that protocol:
“The Swift standard library defines a protocol called Equatable, which
requires any conforming type to implement the equal to operator (==)
and the not equal to operator (!=) to compare any two values of that
type. ”
NSHipster has a couple of relevant posts on this subject:
Swift Default Protocol Implementations
Swift Comparison Protocols
I also found this answer very useful in implementing Equatable:
How do I implement Swift's Comparable protocol?
Alhough it mentions Comparable, Equatable is a subset and the explanation is good.
Excerpts above from: Apple Inc. “The Swift Programming Language.” iBooks. https://itun.es/gb/jEUH0.l
One other option is to use filter:
haystack.filter({$0 == needle}).count > 0
This checks to see if array haystack contains object needle.
You can't. That's why NSArray is still there. However, the Apple documentation reads as follows about String and NSString:
Swift’s String type is bridged seamlessly to Foundation’s NSString
class. If you are working with the Foundation framework in Cocoa or
Cocoa Touch, the entire NSString API is available to call on any
String value you create, in addition to the String features described
in this chapter. You can also use a String value with any API that
requires an NSString instance.
Following that approach, the NSArray API should be available on Array, but it isn't because the native Swift Array is a primitive (most likely a struct or similar), so you have to "convert" it to an NSArray.
It appears that not all of the toll-free bridging from NS/CF space is in place. However, if you declare your array as an NSArray, it works fine:
let fruits: NSArray = [ "apple", "orange", "tomato (really?)" ]
let index = fruits.indexOfObject("orange")
println("Index of Orange: \(index)")
If your array elements are objects and you want to find an identical object in that array, you can use this function:
func findObject<C: CollectionType where C.Generator.Element: AnyObject>(domain: C, value: C.Generator.Element) -> Int? {
for (index, element) in enumerate(domain) {
if element === value {
return index
}
}
return nil
}
As an exercise I am rewriting one of my apps using Swift.
In Objective-C I had the following line of code:
NSRange extendedRange = NSUnionRange(range, [[self.backingStore string]lineRangeForRange:NSMakeRange(NSMaxRange(range), 0)]);
In swift it looks like this:
let str = backingStore.string
let extendedRange: NSRange = NSUnionRange(range, str.lineRangeForRange(NSMakeRange(NSMaxRange(range), 0)))
However, for some reason I am getting 'Int' is not identical to 'String.Index' and I can't figure out why. Any help / insight would be appreciated.
EDIT:
If I bridge my string, it works:
let str = backingStore.string
let extendedRange: NSRange = NSUnionRange(range, str.bridgeToObjectiveC().lineRangeForRange(NSMakeRange(NSMaxRange(range), 0)))
Swift strings are not the same as Foundation strings: they can be bridged, and they may have method names in common, but that does not mean they should be treated as being compatible. Here are two views of the type definition of Swift.String.lineRangeForRange.
Swift.String.lineRangeForRange (Swift.String)(Swift.Range<Swift.String.Index>) -> Swift.Range<Swift.String.Index>
String -> (Range<String.Index>) -> Range<String.Index>
Note also that Swift's Range<T> is start/end while Foundation's NSRange is location/length. There are ways to convert between NSRange and Range<Int>, but a Range<String.Index> is a different story: String.Index is more like an "iterator" than an "index".
What I'd say (and I'm highly pragmatic about this sort of thing) is that if you have a block of code that is based on the semantics of Objective-C strings it might be good to keep using them for a while: get your code working, and then evaluate changing to Swift's String later.
Curious myself, I Cmd+Clicked on String.Index and discovered it is actually defined as a struct in an extension type:
extension String : Collection {
struct Index : BidirectionalIndex {
func succ() -> String.Index
func pred() -> String.Index
}
BidirectionalIndex is a protocol that inherits from another protocol, ForwardIndex.
I assume the succ() and pred() methods stand for 'successor' and 'predecessor' respectively.