How do you call the process of taking a part of a function and making an individual function of it?

Question

I know there was a technical term for this. I'm just can't remember what it was.

If the title needs clarification, here is what I mean; If this is the old code:

Result foobar(Param1,Param2,Param3) {
  code that does abc
  code that does xyz
  code that does asdf
  more code that does something
}

and it's changed into:

SomeResult do_xyz(SomeParams) {
  code that does xyz
}
Result foobar() {
  code that does abc
  do_xyz(args);
  code that does asdf
  more code that does something
}

I'd have called it 'Tidying up'. I can't believe someone decided to call this something special, they must have needed filler for their book. — James, Jul 02 '12 at 23:15
@James: 'tidying up' is a lot more generic. It makes sense to give things that you need to talk about often names, so you can talk about them more efficiently. That is the only reason for patterns. — bitmask, Jul 02 '12 at 23:25

score 21 · Accepted Answer · edited Jul 02 '12 at 20:03

21

Technical term for this is Extract Method

See http://www.refactoring.com/catalog/extractMethod.html

Turn the fragment into a method whose name explains the purpose of the method.

void printOwing() {
    printBanner();

    //print details
    System.out.println ("name:    " + _name);
    System.out.println ("amount    " + getOutstanding());
}

void printOwing() {
    printBanner();
    printDetails(getOutstanding());
}

void printDetails (double outstanding) {
    System.out.println ("name:    " + _name);
    System.out.println ("amount    " + outstanding);
}

edited Jul 02 '12 at 20:03

gnat

21,442
29
112
288

answered Jul 02 '12 at 19:18

herby

2,734
1
18
25

5

*extraction* -- that's it! – bitmask Jul 02 '12 at 19:22
Extract Method. You should check out *Design Patterns*. – Larry Hector Jul 02 '12 at 20:04
9

@LarryHector: I'm not sure it's (GoF) *Design Patterns*. There is thing called Template Method there that is a bit similar, and of course DP is fundamental read, but Extract Method as well as lots of other refactorings are in fact in other piece of literature and that is Martin Fowler's *Refactoring*. – herby Jul 02 '12 at 20:16
1

@herby: You are correct, it is defined in Fowler's *Refactoring*, thanks for the correction. There is also a good section on the how/why of many of the refactoring methods in Michael Feathers' *Working with Legacy Code*. – Larry Hector Jul 03 '12 at 12:37
Some IDE's support this pattern. I usually write big methods, then (in the case of Visual Studio IDE and C#) use the IDE's built-in extractor to select lines of that method to split into separate methods. It has the added benefit forcing you to think about the responsibilities. – Zimano Aug 18 '22 at 14:32

Yusubov · Answer 2 · 2012-07-02T20:25:55.657

8

The process itself is called Refactoring the code, and method is called Extract Method , and it is a good match for applying SRP (single responsibility principle) to the code.

edited Jul 02 '12 at 20:25

answered Jul 02 '12 at 20:01

Yusubov

21,328
6
45
71

Is "Refacturing" a typo? (honest question!) – bitmask Jul 02 '12 at 20:06
@bitmask It most probably is – marktani Jul 02 '12 at 20:07
Yes, it is a typo, as it may seem from the links, it was intended to be "Refactoring" – Yusubov Jul 02 '12 at 20:08
5

Refactoring is less specific. Extract Method is one of many, many kinds of refactoring. And neither one is implicitly related to SRP, although that is one of many reasons you might want to refactor. – pdr Jul 02 '12 at 20:22

How do you call the process of taking a part of a function and making an individual function of it?

2 Answers2

Linked