The protocol to which all class types implicitly conform.

You can use the AnyClass protocol as the concrete type for an instance of any class. When you do, all known @objc class methods and properties are available as implicitly unwrapped optional methods and properties, respectively. For example:

class IntegerRef {
    @objc class func getDefaultValue() -> Int {
        return 42
    }
}

func getDefaultValue(_ c: AnyClass) -> Int? {
    return c.getDefaultValue?()
}

The getDefaultValue(_:) function uses optional chaining to safely call the implicitly unwrapped class method on c. Calling the function with different class types shows how the getDefaultValue() class method is only conditionally available.

print(getDefaultValue(IntegerRef.self))
// Prints "Optional(42)"

print(getDefaultValue(NSString.self))
// Prints "nil"

See Also: AnyObject

A type that provides subscript access to its elements, with bidirectional index traversal.

In most cases, it's best to ignore this protocol and use the BidirectionalCollection protocol instead, because it has a more complete interface.

Deprecated: it will be removed in Swift 4.0. Please use 'BidirectionalCollection' instead.

The default type for an otherwise-unconstrained Boolean literal.

When you create a constant or variable using one of the Boolean literals true or false, the resulting type is determined by the BooleanLiteralType alias. For example:

let isBool = true
print("isBool is a '\(type(of: isBool))'")
// Prints "isBool is a 'Bool'"

The type aliased by BooleanLiteralType must conform to the ExpressibleByBooleanLiteral protocol.

The C '_Bool' and C++ 'bool' type.

The C 'char' type.

This will be the same as either CSignedChar (in the common case) or CUnsignedChar, depending on the platform.

The C++11 'char16_t' type, which has UTF-16 encoding.

The C++11 'char32_t' type, which has UTF-32 encoding.

The C 'double' type.

The C 'float' type.

The C 'int' type.

The C 'short' type.

The C 'signed char' type.

The C 'unsigned char' type.

The C 'unsigned int' type.

The C 'unsigned long' type.

The C 'unsigned long long' type.

The C 'unsigned short' type.

The C++ 'wchar_t' type.

A type that can be initialized by string interpolation with a string literal that includes expressions.

Use string interpolation to include one or more expressions in a string literal, wrapped in a set of parentheses and prefixed by a backslash. For example:

let price = 2
let number = 3
let message = "One cookie: $\(price), \(number) cookies: $\(price * number)."
print(message)
// Prints "One cookie: $2, 3 cookies: $6."

Conforming to the ExpressibleByStringInterpolation Protocol

To use string interpolation to initialize instances of your custom type, implement the required initializers for ExpressibleByStringInterpolation conformance. String interpolation is a multiple-step initialization process. When you use string interpolation, the following steps occur:

1. The string literal is broken into pieces. Each segment of the string literal before, between, and after any included expressions, along with the individual expressions themselves, are passed to the init(stringInterpolationSegment:) initializer.
2. The results of those calls are passed to the init(stringInterpolation:) initializer in the order in which they appear in the string literal.

In other words, initializing the message constant in the example above using string interpolation is equivalent to the following code:

let message = String(stringInterpolation:
      String(stringInterpolationSegment: "One cookie: $"),
      String(stringInterpolationSegment: price),
      String(stringInterpolationSegment: ", "),
      String(stringInterpolationSegment: number),
      String(stringInterpolationSegment: " cookies: $"),
      String(stringInterpolationSegment: price * number),
      String(stringInterpolationSegment: "."))

Deprecated: it will be replaced or redesigned in Swift 4.0. Instead of conforming to 'ExpressibleByStringInterpolation', consider adding an 'init(_:String)'.

The default type for an otherwise-unconstrained Unicode extended grapheme cluster literal.

A 32-bit floating point type.

A 64-bit floating point type.

The default type for an otherwise-unconstrained floating point literal.

A type that provides subscript access to its elements, with forward index traversal.

In most cases, it's best to ignore this protocol and use the Collection protocol instead, because it has a more complete interface.

Deprecated: it will be removed in Swift 4.0. Please use 'Collection' instead.

A type that provides subscript access to its elements, with forward index traversal.

In most cases, it's best to ignore this protocol and use the Collection protocol instead, because it has a more complete interface.

Deprecated: it will be removed in Swift 4.0. Please use 'Collection' instead.

The largest native signed integer type.

The default type for an otherwise-unconstrained integer literal.

A type that provides subscript access to its elements.

In most cases, it's best to ignore this protocol and use the MutableCollection protocol instead, because it has a more complete interface.

Deprecated: it will be removed in Swift 4.0. Please use 'MutableCollection' instead.

A collection that supports efficient random-access index traversal.

In most cases, it's best to ignore this protocol and use the RandomAccessCollection protocol instead, because it has a more complete interface.

Deprecated: it will be removed in Swift 4.0. Please use 'RandomAccessCollection' instead.

A type that supports replacement of an arbitrary subrange of elements with the elements of another collection.

In most cases, it's best to ignore this protocol and use the RangeReplaceableCollection protocol instead, because it has a more complete interface.

Deprecated: it will be removed in Swift 4.0. Please use 'RandomAccessCollection' instead.

Deprecated: it will be replaced or redesigned in Swift 4.0. Instead of conforming to 'StringInterpolationConvertible', consider adding an 'init(_:String)'.

The default type for an otherwise-unconstrained string literal.

The largest native unsigned integer type.

The return type of sequence(first:next:).

The default type for an otherwise-unconstrained unicode scalar literal.

The return type of functions that don't explicitly specify a return type; an empty tuple (i.e., ()).

When declaring a function or method, you don't need to specify a return type if no value will be returned. However, the type of a function, method, or closure always includes a return type, which is Void if otherwise unspecified.

Use Void or an empty tuple as the return type when declaring a closure, function, or method that doesn't return a value.

// No return type declared:
func logMessage(_ s: String) {
    print("Message: \(s)")
}

let logger: (String) -> Void = logMessage
logger("This is a void function")
// Prints "Message: This is a void function"