Clean Code

Why code in an agile conf?

Why clean code?

What is a clean code ?

Clean code is not about beautifullness,
it's about goodness.

Rebecca Wirfs-Brock

measuring cleanness?

make it readable

unreadable

public List<int[]> getFlg() {
  List<int[]> list1 = new ArrayList<int[]>();
  for (int[] x : theList ) {
    if (x[0] == 4)
      list1.add(x);
  }
	
  return list1;
}
					

much better!

public List<Cell> getFlaggedCells() {
  List<Cell> flaggedCells = new ArrayList<Cell>();
  for (Cell cell : gameBoard ) {
    if (cell.isFlagged())
      flaggedCells.add(cell);
  }
		
  return flaggedCells;
}	
					

unreadable

public RGBColor readCurrentColor(BlinkLed led) {
    device.sendCommand(new ReadColorRequest(led));
    
    byte[] response = device.readResponse();

    int red = response[2] >= 0 ? response[2] : response[2] + 256;
    int green = response[3] >= 0 ? response[3] : response[3] + 256;
    int blue = response[4] >= 0 ? response[4] : response[4] + 256;
        
    return new RGBColor(red, green, blue);
}
				

extract code

much better!

public RGBColor readCurrentColor(BlinkLed led) {
    device.sendCommand(new ReadColorRequest(led));
    byte[] response = device.readResponse();
    
    return extractColor(response);
}

private RGBColor extractColor(byte[] response) {
    int red = convertToPositiveInt(response[2]);
    int green = convertToPositiveInt(response[3]);
    int blue = convertToPositiveInt(response[4]);

    return new RGBColor(red, green, blue);
}

private int convertToPositiveInt(byte byt) {
    return byt >= 0 ? byt : byt + 256;
}

Comments

false good idea

comments in real life

/*
* A comment to please checkstyle
*/

/*
* Set the port
*
* @params port
*/
public void setPort(Port port) {this.port=port}

...
        } /* end for */
        dao.flush();
      default : 
        break;  
      } /* end switch */
    } /* end if */
  } /* end if */
} catch ...

Comments are always failure

Uncle Bob

Don't comment bad code. Rewrite it.

Brian W. Kernighan, P.J. Plaugher

Comments : the exception

explain the Why!

Comments

Tests tells me What

Code tells me How

Comment, if needed, tells me why

Tests

They give you confidence to change the code.

tests document your code

Tests are first class citizens!

by the way

Test everything!

coupling

this is bad

a.getB().getC().doThings(); // this is bad
				

a.doThings();
					

Demeter's Law

public class Client {
  private Service service;

  public Client() {
    this.service = new ServiceExample();
  }

  public String greet() {
    return "Hello " + service.getName();
  }
}    
                

bad

Dependency Injection

public class Client {
  private Service service;

  public Client(Service service) {
    this.service = service;
  }

  public String greet() {
    return "Hello " + service.getName();
  }
}    
                

better

Dependency injection frameworks

they can be dangerous

really. Please.

don't let them go inside your business

try wishfull design

and you can do that for you whole application!

maybe, you should :)

some smells

lots of other good stuff

• SOLID principles are good for you
• never ever return null
• do not check exceptions
• do not always think inheritance, think composition
• do not think if/switch, think polymorphism
• avoid singletons
• ...

a clean code

• is tested !
• has no duplication
• reveals its intention
• easy to read

B. Stroustrup, R. Jeffries, K. Beck, M. Feathers, W. Cunningham, ...

Continuous attention to technical excellence and good design enhances agility.

Agile Manifesto

Read list

Thanks!

For questions, we'll be there the whole day,
just come and talk to us.

Slides will be available here very soon:
http://avernois.github.io/prez-clean_code/