/Refactoring /Refactoring techniques /Simplifying Method Calls

Replace Parameter with Explicit Methods

Problem

A method is split into parts, each of which is run depending on the value of a parameter.

Solution

Extract the individual parts of the method into their own methods and call them instead of the original method.

Before

void setValue(String name, int value) {  if (name.equals("height")) {    height = value;    return;  }  if (name.equals("width")) {    width = value;    return;  }  Assert.shouldNeverReachHere();}

After

void setHeight(int arg) {  height = arg;}void setWidth(int arg) {  width = arg;}

Before

void SetValue(string name, int value) {  if (name.Equals("height"))   {    height = value;    return;  }  if (name.Equals("width"))   {    width = value;    return;  }  Assert.Fail();}

After

void SetHeight(int arg) {  height = arg;}void SetWidth(int arg) {  width = arg;}

Before

function setValue($name, $value) {  if ($name === "height") {    $this->height = $value;    return;  }  if ($name === "width") {    $this->width = $value;    return;  }  assert("Should never reach here");}

After

function setHeight($arg) {  $this->height = $arg;}function setWidth($arg) {  $this->width = $arg;}

Before

def output(self, name):    if name == "banner"        # Print the banner.        # ...    if name == "info"        # Print the info.        # ...

After

def outputBanner(self):    # Print the banner.    # ...def outputInfo(self):    # Print the info.    # ...

Before

 setValue(name: string, value: number): void {  if (name.equals("height")) {    height = value;    return;  }  if (name.equals("width")) {    width = value;    return;  }  }

After

setHeight(arg: number): void {  height = arg;}setWidth(arg: number): number {  width = arg;}

Why Refactor

A method containing parameter-dependent variants has grown massive. Non-trivial code is run in each branch and new variants are added very rarely.

Benefits

Improves code readability. It is much easier to understand the purpose ofstartEngine() thansetValue("engineEnabled", true).

When Not to Use

Do not replace a parameter with explicit methods if a method is rarely changed and new variants are not added inside it.

How to Refactor

For each variant of the method, create a separate method. Run these methods based on the value of a parameter in the main method.
Find all places where the original method is called. In these places, place a call for one of the new parameter-dependent variants.
When no calls to the original method remain, delete it.