---
title: AnyObject
framework: swift
role: symbol
role_heading: Type Alias
path: swift/anyobject
---

# AnyObject

The protocol to which all classes implicitly conform.

## Declaration

```swift
typealias AnyObject
```

## Discussion

Discussion You use AnyObject when you need the flexibility of an untyped object or when you use bridged Objective-C methods and properties that return an untyped result. AnyObject can be used as the concrete type for an instance of any class, class type, or class-only protocol. For example: class FloatRef {     let value: Float     init(_ value: Float) {         self.value = value     } }

let x = FloatRef(2.3) let y: AnyObject = x let z: AnyObject = FloatRef.self AnyObject can also be used as the concrete type for an instance of a type that bridges to an Objective-C class. Many value types in Swift bridge to Objective-C counterparts, like String and Int. let s: AnyObject = "This is a bridged string." as NSString print(s is NSString) // Prints "true"

let v: AnyObject = 100 as NSNumber print(type(of: v)) // Prints "__NSCFNumber" The flexible behavior of the AnyObject protocol is similar to Objective-C’s id type. For this reason, imported Objective-C types frequently use AnyObject as the type for properties, method parameters, and return values. Casting AnyObject Instances to a Known Type Objects with a concrete type of AnyObject maintain a specific dynamic type and can be cast to that type using one of the type-cast operators (as, as?, or as!). This example uses the conditional downcast operator (as?) to conditionally cast the s constant declared above to an instance of Swift’s String type. if let message = s as? String {     print("Successful cast to String: \(message)") } // Prints "Successful cast to String: This is a bridged string." If you have prior knowledge that an AnyObject instance has a particular type, you can use the unconditional downcast operator (as!). Performing an invalid cast triggers a runtime error. let message = s as! String print("Successful cast to String: \(message)") // Prints "Successful cast to String: This is a bridged string."

let badCase = v as! String // Runtime error Casting is always safe in the context of a switch statement. let mixedArray: [AnyObject] = [s, v] for object in mixedArray {     switch object {     case let x as String:         print("'\(x)' is a String")     default:         print("'\(object)' is not a String")     } } // Prints "'This is a bridged string.' is a String" // Prints "'100' is not a String" Accessing Objective-C Methods and Properties When you use AnyObject as a concrete type, you have at your disposal every @objc method and property—that is, methods and properties imported from Objective-C or marked with the @objc attribute. Because Swift can’t guarantee at compile time that these methods and properties are actually available on an AnyObject instance’s underlying type, these @objc symbols are available as implicitly unwrapped optional methods and properties, respectively. This example defines an IntegerRef type with an @objc method named getIntegerValue(). class IntegerRef {     let value: Int     init(_ value: Int) {         self.value = value     }

@objc func getIntegerValue() -> Int {         return value     } }

func getObject() -> AnyObject {     return IntegerRef(100) }

let obj: AnyObject = getObject() In the example, obj has a static type of AnyObject and a dynamic type of IntegerRef. You can use optional chaining to call the @objc method getIntegerValue() on obj safely. If you’re sure of the dynamic type of obj, you can call getIntegerValue() directly. let possibleValue = obj.getIntegerValue?() print(possibleValue) // Prints "Optional(100)"

let certainValue = obj.getIntegerValue() print(certainValue) // Prints "100" If the dynamic type of obj doesn’t implement a getIntegerValue() method, the system returns a runtime error when you initialize certainValue. Alternatively, if you need to test whether obj.getIntegerValue() exists, use optional binding before calling the method. if let f = obj.getIntegerValue {     print("The value of 'obj' is \(f())") } else {     print("'obj' does not have a 'getIntegerValue()' method") } // Prints "The value of 'obj' is 100"

## See Also

### Existential Types

- [AnyClass](swift/anyclass.md)