Webcast: Identify and Correct Common Code Smells

Identify and CorrectCommon Code Smells

11/12/2014

http://submain.com/webcasts/identify-and-correct-common-code-smells/

for the webcast recording and slides download

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11/12/2014 Copyright © SubMain 2014 Slide 2

Introduction

Presenter

Steve Smith

Microsoft MVP, RDCTO, Falafel Software

(g)host

Serge Baranovsky

Chief Strategy Officer, SubMain

11/12/2014 Copyright © SubMain 2014 3

Steve Smith

Pluralsight Author SOLID Principles, Design Patterns

DDD, N-Tier Architecture

Kanban, Web Performance Tuning/Testing

Refactoring and Code Smells

Blog Ardalis.com

More http://about.me/stevenasmith


@ardalis

StevenAndrewSmith

stevenandrewsmith

What are ‘Code Smells’ ?


Bad Smells in Code

Described by Kent Beck and Martin Fowler in Refactoring Fundamentals

Intentionally vague term

Context-dependent; use your judgment


Principle of Least Surprise

Design your API to behave as programmers would expect


Kent Beck’s Rules of Simple Design

Well-designed code should:

Run all the tests (successfully)

Contain no duplicate code

Express all the ideas its authors wish to express

Minimize classes and methods


Code Smell: Long Method

Prefer short methods to long methods Smaller methods can have more descriptive names

Smaller methods are easier to understand at a glance

Less likely to duplicate code between small methods

Strive for no more than 10 lines of code per method

Do not tolerate methods that do not fit on one screen


Example: Long Method


Code Smell: Large Class

Similar to Long Method

Usually violates Single Responsibility Principle

May have Too many instance variables Too many methodsAll of the above

Typically lacks cohesion Several classes baked into one


Code Smell: Primitive Obsession

Abusing primitives instead of using better abstractions

Less intention-revealing

Leads to scattered business logicGuard clauses

Validation


Example: Primitive Obsession

// method call relying on primitives only

AddHoliday(7,4);



// method call relying on primitives only

AddHoliday(7,4);

// use a higher level type

Date independenceDay = new Date(7,4);

AddHoliday(independenceDay);



// go even further

public class July {

private const int _month = 7;

public static readonly Date Fourth {

get { return new Date(_month, 4); } } }

AddHoliday(July.Fourth);



// method call relying on primitives

DrawLine(5,20,25,40);




DrawLine(5,20,25,40,0,0,255);




TransferFunds(23423, 23434, 48432);




TransferFunds(23423, 23434, 48432);

// refactored to be more clear and use higher level objects

Account transferFrom = _accountRepository.Get(23423);

Account transferTo = _accountRepository.Get(23434);

var transferAmount = new Money(48432, Currency.USD);

TransferFunds(transferFrom, transferTo, transferAmount);


Primitive Obsession Common Examples

Phone Numbers

Social Security Numbers

ZIP/Postal Codes

Money

Age

Temperature

Address

Credit Card Information


Code Smell: Data Clumps

Sets of data items that are always used together, but are not organized together

Similar to Primitive Obsession, but always deals with several items

Frequently give rise to long parameter lists (another smell)


Example: Data Clumps

// data clumps on an order

Order.CreditCardName = creditCardName;

Order.CreditCardNumber = creditCardNumber;

Order.ExpiresMonth = creditCardMonth;

Order.ExpiresYear = creditCardYear;

Order.SecurityCode = creditCardSecurityCode;


Example: Data Clumps

// data clumps on an order

Order.CreditCardName = creditCardName;

Order.CreditCardNumber = creditCardNumber;

Order.ExpiresMonth = creditCardMonth;

Order.ExpiresYear = creditCardYear;

Order.SecurityCode = creditCardSecurityCode;

// refactored by Extracting a new CreditCardInfo class

CreditCardInfo cardInfo = new CreditCardInfo(

creditCardNme, creditCardNumber, creditCardMonth,

creditCardYear, creditCardSecurityCode);

Order.CreditCard = cardInfo;


Code Smell: Poor Names

Names should:

Be descriptive

Be at appropriate abstraction level

Use standard terms

Be unambiguous

Avoid encodings

Describe side effects

Be longer when scope is large


Example: Poor Names

public static List<int> Generate(int n)

{

var x = new List<int>();

for (int i = 2; n > 1; i++)

for (; n % i == 0; n /= i)

x.Add(i);

return x;

}


Example: Poor Names

public static List<int> GeneratePrimeFactorsOf(int input)

{

var primeFactors = new List<int>();

for (int candidateFactor = 2; input > 1; candidateFactor++)

while (input % candidateFactor == 0)

{

primeFactors.Add(candidateFactor);

input /= candidateFactor;

}

return primeFactors;

}

// Usage:

var factors = GeneratePrimeFactorsOf(input);


Example: Inappropriate Abstraction Level

public class User

{

public string UserName { get; set; }

public static int GetTotalUserCountInDatabaseTable()

{

throw new NotImplementedException();

}

public static SqlDataReader GetDataReaderWithRoles(string userName)

{


}

}


Example: Inappropriate Abstraction Level

public class User

{

public string UserName { get; set; }

public IEnumerable<Role> IsInRoles()

{


}

}


public class SqlUserRepository

{

public int TotalUserCount()

{


}

public IEnumerable<Role> UserIsInRoles(string userName)

{


}

}

How CodeIt.Right Helps


What is CodeIt.Right

Code Quality Analysis and Metrics

Automated Code Review process

Automated way to discover and fix code smells

Automatic and safe refactoringof issues into conforming code

Ensure your code adheres to (your) predefined design requirements and best coding practices


What is CodeIt.Right - continued

Instant Code Review – real-time code checking

OnDemand Analysis

Source Control Check-In Policy

Build Process Integration

Hundreds of rules Security, Performance, Usage,

Design, Maintainability, Exception Handling, Globalization, Async, and more


Demo

Discover and Fix Code Smells

Coding Pattern Examples ISerializable/Custom Serialization

Dispose/Finalize


Q&A

Questions?

Email - [email protected]

Video - submain.com/codeit.right/video

Download the free CodeIt.Right trial at submain.com/codeit.right


1 (800) 936-2134

http://submain.com/webcasts/identify-and-correct-common-code-smells/

for the webcast recording and slides download