How can I tell what the class of an instance variable is in Swift

Question

Is there any easy way to tell what class an instance variable is in a Swift? In the JVM-based languages that I'm used to, you can do something like println(value.class) to get it's class.

Is there something equivalent in Swift?

The closest thing I can find in the docs is the ability to do "type checking" with the is <Class> keyword but that only helps me guess a little bit.

I've run into a few situations in playing around where I thought I had one type of class, but actually had another and didn't know how to know for sure.

Answer 1

Use type.self to return a type that can be passed into a method that accepts a type-level argument. For example, UILabel.self can be passed to the isKindOfClass method call. The string representation of the class can be found via dynamicType.description():

var label = UILabel()
println(label.dynamicType.description())
println(label.isKindOfClass(UILabel.self))

Swift-3

var label = UILabel()
println(type(of: label).description())

Output
UILabel
true

Here's a bit more background -- there are two expressions to be aware of: the postfix self expression and the dynamic type expression. From the docs:

Postfix Self
A postfix self expression consists of an expression or the name of a type, immediately followed by .self. It has the following forms:

expression.self
type.self

The first form evaluates to the value of the expression. For example, x.self evaluates to x.

The second form evaluates to the value of the type. Use this form to access a type as a value. For example, because SomeClass.self evaluates to the SomeClass type itself, you can pass it to a function or method that accepts a type-level argument

Dyamic Type Expression
A dynamicType expression consists of an expression, immediately followed by .dynamicType. It has the following form:

expression.dynamicType

The expression can’t be the name of a type. The entire dynamicType expression evaluates to the value of the runtime type of the expression.