Refactoring/SimplifyingConditionalExpressions - Revision history

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← Older revision		Revision as of 00:29, 27 March 2026
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	_primaryProject.getMemberExpenseLimit();		_primaryProject.getMemberExpenseLimit();
	----		----
	[[Refactoring]]		Refactoring

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	= Chapter 9 Simplifying Conditional Expressions =		= Chapter 9 Simplifying Conditional Expressions =
	== Decompose Conditional ==		== Decompose Conditional ==
	* You have a complicated conditional (if-then-else) statement. ''Extract methods from the condition, then part, and else parts.''		* You have a complicated conditional (if-then-else) statement. <br /> ''Extract methods from the condition, then part, and else parts.''
	if (data.before( SUMMER_START ) \|\| data.after(SUMMER_END) )		if (data.before( SUMMER_START ) \|\| data.after(SUMMER_END) )
	charge = quantity * _winterRate + _winterServeceCharge;		charge = quantity * _winterRate + _winterServeceCharge;
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	else charge = summerCharge(quatity);		else charge = summerCharge(quatity);
	== Consolidate Conditional Expression ==		== Consolidate Conditional Expression ==
	* You have a sequence of conditional tests with the same result. ''Combine them into a single conditional expression and extract it.''		* You have a sequence of conditional tests with the same result. <br />''Combine them into a single conditional expression and extract it.''
	double disabilityAmount() {		double disabilityAmount() {
	if (_seniority < 2) return 0;		if (_seniority < 2) return 0;
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	// compute the disability amount;		// compute the disability amount;
	== Consolidate Duplicate Conditional Fragments ==		== Consolidate Duplicate Conditional Fragments ==
	* The same fragment of code is in all branches of a conditional expression. ''Move it outside of the expression.''		* The same fragment of code is in all branches of a conditional expression. <br />''Move it outside of the expression.''
	if (isSpecialDeal()){		if (isSpecialDeal()){
	total = price * 0.95;		total = price * 0.95;
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	send();		send();
	== Replace Nested Conditional with Guard Clauses ==		== Replace Nested Conditional with Guard Clauses ==
	* A method has conditional behavior that does not make clear the normal path of execution ''Use guard clauses for all the special cases.''		* A method has conditional behavior that does not make clear the normal path of execution <br /> ''Use guard clauses for all the special cases.''
	double getPayAmount(){		double getPayAmount(){
	double result;		double result;
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	return normalPayAmount();		return normalPayAmount();
	== Replace Conditional with Polymorphism ==		== Replace Conditional with Polymorphism ==
	* You have a conditional that chooses different behavior depending on the type of and object ''Move each leg of the conditional to an overriding method in a subclass. Make the orginal method abstract.''		* You have a conditional that chooses different behavior depending on the type of and object <br /> ''Move each leg of the conditional to an overriding method in a subclass. Make the orginal method abstract.''
	double getSpeed() {		double getSpeed() {
	switch (_type) {		switch (_type) {
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	== Introduce Null Object ==		== Introduce Null Object ==
	* You have repeated checks for a null value ''Replace the null value with a null object.''		* You have repeated checks for a null value<br /> ''Replace the null value with a null object.''
	if (customer == null) plan = BillingPlan.basic();		if (customer == null) plan = BillingPlan.basic();
	else plan = customer.getPlan();		else plan = customer.getPlan();
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	== Introduce Assertion ==		== Introduce Assertion ==
	* A section of code assumes something about the state of the program. ''Make the assumption explicit with an assertion.''		* A section of code assumes something about the state of the program. <br />''Make the assumption explicit with an assertion.''
	double getExpenseLimit() {		double getExpenseLimit() {
	//should have eigher expense limit or a primary project		//should have eigher expense limit or a primary project
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	----		----
	[[Refactoring]]		[[Refactoring]]

imported>Unknown at 05:27, 7 February 2021

2021-02-07T05:27:53Z

New page

__TOC__
= Chapter 9 Simplifying Conditional Expressions =
== Decompose Conditional ==
* You have a complicated conditional (if-then-else) statement. ''Extract methods from the condition, then part, and else parts.''
if (data.before( SUMMER_START ) || data.after(SUMMER_END) )
charge = quantity * _winterRate + _winterServeceCharge;
else charge = quantity * _summerRate;

if (notSummer(date))
charge = winterCharge(quantity);
else charge = summerCharge(quatity);
== Consolidate Conditional Expression ==
* You have a sequence of conditional tests with the same result. ''Combine them into a single conditional expression and extract it.''
double disabilityAmount() {
if (_seniority < 2) return 0;
if ( _monthsDisabled > 12) return 0;
if ( _isPartTime) return 0;
// compute the disability amount
double disabilityAmount() {
if( isNotEligableForDisability()) return 0;
// compute the disability amount;
== Consolidate Duplicate Conditional Fragments ==
* The same fragment of code is in all branches of a conditional expression. ''Move it outside of the expression.''
if (isSpecialDeal()){
total = price * 0.95;
send();
}
else {
total = price * 0.98;
send();
}
if (isSpecialDeal())
total = price * 0.95
else
total = price * 0.98;
send();
== Replace Nested Conditional with Guard Clauses ==
* A method has conditional behavior that does not make clear the normal path of execution ''Use guard clauses for all the special cases.''
double getPayAmount(){
double result;
if( _isDead) result = deadAmount();
else {
if (_isSeparated) result = separatedAmount();
else {
if (_isRetried) result = retiredAmount();
else result = normalPayAmount();
};
}
return result;

double getPayAmount() {
if (_isDead) return deadAmount();
if (_isSeparated) return separatedAmount();
if (_isRetried) return retiredAmount();
return normalPayAmount();
== Replace Conditional with Polymorphism ==
* You have a conditional that chooses different behavior depending on the type of and object ''Move each leg of the conditional to an overriding method in a subclass. Make the orginal method abstract.''
double getSpeed() {
switch (_type) {
case EUROPEAN:
return getBaseSpeed();
case AFRICAN:
return getBaseSpeed() - getLoadFactor() * _numberofCoconuts;
case NORWEGIAN_BLUE:
return (_isNailed) ? 0 : getBaseSpeed(_voltage);
}
throw new RuntimeException ("Should be unreachable");
}

┌─────┐
│ Bird │
├─────┤
│getSpeed │
└─────┘
△
│
┌───────┼─────────┐
│ │ │
┌──┴──┐ ┌──┴──┐ ┌────┴──┐
│European| │ │African │ │Norwegian Blue│
├─────┤ ├─────┤ ├───────┤
│getSpeed │ │getSpeed │ │getSpeed │
└─────┘ └─────┘ └───────┘

== Introduce Null Object ==
* You have repeated checks for a null value ''Replace the null value with a null object.''
if (customer == null) plan = BillingPlan.basic();
else plan = customer.getPlan();
┌───────┐
│ Cutomer │
├───────┤
│getPlan │
└───────┘
△
│
┌───┴───┐
│Null Customer │
├───────┤
│getPlan │
└───────┘

== Introduce Assertion ==
* A section of code assumes something about the state of the program. ''Make the assumption explicit with an assertion.''
double getExpenseLimit() {
//should have eigher expense limit or a primary project
return (_expenseLimit != NULL_EXPENSE)?
_expenseLimit:
_primaryProject.getMemberExpenseLimit();
}
double getExpenseLimit() {
Assert.isTrue( _expenseLimit != NULL_EXPENSE || _primaryProject != null );
return (_expenseLimit != NULL_EXPENSE)?
_expenseLimit:
_primaryProject.getMemberExpenseLimit();
----
[[Refactoring]]