Function

class_addMethod(_:_:_:_:)

Adds a new method to a class with a given name and implementation.

Declaration

func class_addMethod(_ cls: AnyClass?, _ name: Selector, _ imp: IMP, _ types: UnsafePointer<Int8>?) -> Bool

Parameters

cls

The class to which to add a method.

name

A selector that specifies the name of the method being added.

imp

A function which is the implementation of the new method. The function must take at least two arguments—self and _cmd.

types

An array of characters that describe the types of the arguments to the method. For possible values, see Objective-C Runtime Programming Guide > Type Encodings. Since the function must take at least two arguments—self and _cmd, the second and third characters must be “@:” (the first character is the return type).

Return Value

true if the method was added successfully, otherwise false (for example, the class already contains a method implementation with that name).

Discussion

class_addMethod(_:_:_:_:) will add an override of a superclass's implementation, but will not replace an existing implementation in this class. To change an existing implementation, use method_setImplementation(_:_:).

An Objective-C method is simply a C function that take at least two arguments—self and _cmd. For example, given the following function:

void myMethodIMP(id self, SEL _cmd)
{
    // implementation ....
}

you can dynamically add it to a class as a method (called resolveThisMethodDynamically) like this:

class_addMethod([self class], @selector(resolveThisMethodDynamically), (IMP) myMethodIMP, "v@:");

See Also

Working with Classes

func class_getName(AnyClass?)

Returns the name of a class.

func class_getSuperclass(AnyClass?)

Returns the superclass of a class.

func class_setSuperclass(AnyClass, AnyClass)

Sets the superclass of a given class.

Deprecated
func class_isMetaClass(AnyClass?)

Returns a Boolean value that indicates whether a class object is a metaclass.

func class_getInstanceSize(AnyClass?)

Returns the size of instances of a class.

func class_getInstanceVariable(AnyClass?, UnsafePointer<Int8>)

Returns the Ivar for a specified instance variable of a given class.

func class_getClassVariable(AnyClass?, UnsafePointer<Int8>)

Returns the Ivar for a specified class variable of a given class.

func class_copyIvarList(AnyClass?, UnsafeMutablePointer<UInt32>?)

Describes the instance variables declared by a class.

func class_getIvarLayout(AnyClass?)

Returns a description of the Ivar layout for a given class.

func class_setIvarLayout(AnyClass?, UnsafePointer<UInt8>?)

Sets the Ivar layout for a given class.

func class_getWeakIvarLayout(AnyClass?)

Returns a description of the layout of weak Ivars for a given class.

func class_setWeakIvarLayout(AnyClass?, UnsafePointer<UInt8>?)

Sets the layout for weak Ivars for a given class.

func class_getProperty(AnyClass?, UnsafePointer<Int8>)

Returns a property with a given name of a given class.

func class_getInstanceMethod(AnyClass?, Selector)

Returns a specified instance method for a given class.

func class_getClassMethod(AnyClass?, Selector)

Returns a pointer to the data structure describing a given class method for a given class.

func class_copyMethodList(AnyClass?, UnsafeMutablePointer<UInt32>?)

Describes the instance methods implemented by a class.

func class_replaceMethod(AnyClass?, Selector, IMP, UnsafePointer<Int8>?)

Replaces the implementation of a method for a given class.

func class_getMethodImplementation(AnyClass?, Selector)

Returns the function pointer that would be called if a particular message were sent to an instance of a class.

func class_getMethodImplementation_stret(AnyClass?, Selector)

Returns the function pointer that would be called if a particular message were sent to an instance of a class.

func class_respondsToSelector(AnyClass?, Selector)

Returns a Boolean value that indicates whether instances of a class respond to a particular selector.

func class_conformsToProtocol(AnyClass?, Protocol?)

Returns a Boolean value that indicates whether a class conforms to a given protocol.

func class_getVersion(AnyClass?)

Returns the version number of a class definition.

func class_setVersion(AnyClass?, Int32)

Sets the version number of a class definition.