Nested boolean conditions express a business rule. Not an IF

TL;DR: Avoid checking for boolean expressions and returning an explicit boolean.

Problems

• Declarativeness

• Ninja Code

• Readability

• Arrow Code

Solutions

1. Return a boolean business formula value.

Context

When dealing with boolean formulas, it is more readable to show a business boolean formula than a stair of boolean checks followed by returning an explicit true/false;

Sample Code

Wrong

def is_platypus(self):
    if self.is_mammal():
        if self.has_fur():
            if self.has_beak():
                if self.has_tail():
                    if self.can_swim():
                        return True
    return False

# This is also wrong since it is polluted with IFs and not readable by a biologist
def is_platypus(self):
    if not self.is_mammal():
        return False
    if not self.has_fur():
        return False
    if not self.has_beak():
        return False
    if not self.has_tail():
        return False
    if not self.can_swim():
        return False 
    return True

Right

def is_platypus(self):
    return self.is_mammal() &&  self.has_fur() && self.has_beak() && self.has_tail() && self.can_swim()

#We can even group conditions according to animal taxonomies

Detection

[X] Automatic

Based on syntax trees, we can safely refactor the code removing the explicit boolean value.

Tags

• Boolean

Conclusion

Beware of returning booleans.

After the return, you will need an If statement which is also a code smell.

Relations

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Code Smell 80 - Nested Try/Catch

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More Info

• How to Get Rid of Annoying Ifs Forever

Credits

Photo by Jukan Tateisi on Unsplash

Thanks again to Nico K. for this suggestion.

The real hero of programming is the one who writes negative code.

Douglas McIlroy

Software Engineering Great Quotes

Maxi Contieri ・ Dec 28 '20

#codenewbie #programming #quotes #software

This article is part of the CodeSmell Series.

How to Find the Stinky parts of your Code

Maxi Contieri ・ May 21 '21

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