Refactoring

[rain1024]

The Rule of Three

Fowler, M. and Beck, K. (1999). Refactoring. 1st ed. Reading, MA: Addison-Wesley.

• The first time you do something you just do it.
• The second time you do something similar, you wince at the duplication, but you do the duplicate thing anyway.
• The third time you do something similar, you refactor.

  When

• add funciton
• need to fix a bug
• do code review

  When not

• the existing code is such a mess
• close to deadline

  Bad Smells

Duplicated Code | Long Method | Large Class | Long Parameter List | Divergent Change | Shotgun | Surgery | Feature Envy | Data Clumps | Primitive Obsession | Switch Statements | Parallel Inheritance | Hierarchies | Lazy Class | Speculative Generality | Temporary Field | Message Chains | Middle Man | Inappropriate Intimacy | Alternative Classes with Different Interfaces | Incomplete Library Class | Data Class | Refused Bequest | Comments

Composite Methods

Moving Features Between Objects

Organizing Data

Simplifying Conditional Expressions

Making Method Calls Simpler

Dealing with Generalization

Big Refactorings

Process

First Step: build a solid set of tests

References

• Slideshare.net, (2014). Refactoring Tips by Martin Fowler. [online] Available at: http://www.slideshare.net/redigon/refactoring-1658371 [Accessed 25 Jun. 2014].
• Sourcemaking.com, (2014). Code smells. [online] Available at: http://sourcemaking.com/refactoring/bad-smells-in-code [Accessed 25 Jun. 2014].

[rain1024]

Methods

M1. Extract Method

//  Before refactoring
void printOwing(double mount){
   printBanner();
   // print details
   WriteLine("name: " + name);
   WriteLine("amount: " + amount);
}

//  After refactoring
void printOwing(double mount){
   printBanner();
   printDetails();
}

void printDetails(double mount){
   WriteLine("name: " + name);
   WriteLine("amount: " + amount);
}

M2. Inline Method