Writing Clean Code. Functions and Methods(Part 2).

This article will show you how clean functions can help you avoid duplicated code, avoid indentation(or arrow code) and mark real intent. After that we’ll show you some tips for improving your functions.

The main difference between a method and a function is that a method is on an object. A function is independent of an object. In this article functions and methods are the same thing.

Functions are often viewed as simple blocks of code, meant to avoid duplicated code. This article will show that clean functions are way more complex than that, find out more!

Main Reasons To Create A Function:

1. Avoid Duplicated Code.

• Duplicated code means there are 2 places which have to be fixed/maintained.
• Usually developer think this is the only reason a function should be created(It’s not).

2. Avoid Indentation (or Arrow Code).

Look at the code above:

if
  if
    if
      while
        do something
      end while
    endif
  endif
endif

Cons:

• Adds noise, this is a sign that the code is complicated.
• Readability is damaged, more time is needed to understand it.
• Hard to test.
• More chances for having bugs.

Solutions:

• Solution 1: Extract the method.

Dirty:

if
  if
    if 
      while
        do something magic
      endwhile
    endif
  endif
endif

Clean:

if
  if
    if 
      doSomethingMagic()
    endif
  endif
endif
function doSomethingMagic
  while
    do something magic
  end while
endfunction

• Solution 2: Return early.

Dirty:

function isValid
  if condition1
    if condition2
      if condition3
        return true
      endif
    endif
  endif
endfunction

Clean:

function isValid
  if !condition1
    return false
  endif
  if !condition2
    return false
  endif
  return condition3
endfunction

• Solution 3: Throw The Error Fast.

Dirty:

function signUpUser
  if !isUsernameValid(username)
    if !isPasswordValid(password)
      // account is created
    else
      throw new error Username is Invalid
    endif
  else
    throw new error Password is Invalid
  endif
endfunction

Clean:

function signUpUser
  if !isUsernameValid(username)
    throw new error Username is Invalid   
  if !isPasswordValid(password)
    throw new error Password is Invalid
  // account is created
endfunction

3. Mark The Real Intent.

Understanding the intent of a function is really important. Comments are often a good solution, but a good name for your function is a better one.
The function name acts as a short summary, choose it well.

Dirty:

if isUsernameValid(username) && isPasswordValid(password)
  // signUpUser

Clean:

if isUserValid(username, password)
  // signUpUser
function isUserValid
  return isUsernameValid(username) && isPasswordValid(password)
  // account is created
endfunction

Tips for Improving your Functions:

• Pick the correct name, and mark real intent. For some tips in doing that read this article about Writing Clean Code. Proper Naming for variables, methods and classes.
• Stick to the Single Responsibility Rule. Also, picking the name is easy if the function does only 1 task.
• Avoid Indentation or Arrow Code(showed above how).
• Return early(showed above how).
• Throw the Error Fast(showed above how).
• Stick to the 7 rule: Most adults can store between 5 and 9 items in their short-term memory. The function is easier to understand if it doesn’t have more than 7 variables/conditionals/parameters/etc.
• Reduce the number of parameters as much as you can. Few parameters are easier to understand and test. A solution here is to pass objects and not variables.
• Handle exception at the root level, don’t allow for try and catch blocks to spawn like baby rabbits.

Published at https://flawless-bits.com/blog/clean-code-functions-and-methods.
Have a Great Day!