Refactoring

Chapter 7 Moving Features Between Objects

Move Method

A method is, or will be, using or used by more features of another class than the class on which it is defined.

Create a new method with a similar body in the class it uses most. Either turn the old method into a simple delegation, or remove it altogether.

http://zeropage.org/~reset/zb/data/MoveMethod.gif

Move Field

A field is, or will be, used by another class more than the class on which it is defined.

Create a new field in the target class, and change all its users.

http://zeropage.org/~reset/zb/data/MoveField.gif

Extract Class

You have one class doing work that should be done by two.

Create a new class and move the relevant fields and methods from the old class into the new class.

http://zeropage.org/~reset/zb/data/1012450988/ExtractClass.gif

Inline Class

A class isn't doing very much.

Move all its features into another class and delete it.

http://zeropage.org/~reset/zb/data/InlineClass.gif

Hide Delegate

A client is calling a delegate class of an object.

Create methods on the server to hide the delegate.

http://zeropage.org/~reset/zb/data/HideDelegate.gif

Remove Middle Man

A class is doing too much simple delegation.

Get the client to call the delegate directly.

http://zeropage.org/~reset/zb/data/RemoveMiddleMan.gif

Introduce Foreign Method

A server class you are using needs an additional method, but you can't modify the class.

Create a method in the client class with an instance of the server class as its first argument.

Date newStart = new Date (previousEnd.getYear(), previousEnd.getMonth(), previousEnd.getDate() + 1);

Date newStart = nextDay (previousEnd);

private static Date nextDay (Date arg) {
	return new Date (arg.getYear(), arg.getMonth(), arg.getDate() + 1);
}

Introduce Local Extension

A server class you are using needs serveral additional methods, but you can't modify the class.

Create a new class that contains these extra methods. Make the extension class a subclass or a wapper of the original.

http://zeropage.org/~reset/zb/data/IntroduceLocalExtension.gif

Refactoring