How do I print the type or class of a variable in Swift?

swift, types

Solution

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.

Problem

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!`.

Original source

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