Temporary Field

Temporary Field is a variable created where it is not needed. It refers to variables only used in some situations [1] or specific areas of a program. This uniqueness can be confusing when the purpose of using the variable cannot be explained or cannot be found outside of its scope [2]. It might be misplaced at the class level when the functionality it provides is specific only to a particular method [2]. One should expect an object to need all of its fields.

Problems

Hard to Understand

Additional fields clutter the code and strain the cognitive load by keeping in mind useless attributes.

Examples

@dataclass
class MyDateTime:
    def __init__(self, year, month, day):
        self.year = year
        self.month = month
        self.day = day
        self.full_date = f"{year}, {month}, {day}"

    def foo(self):
        ...

    def goo(self):
        ...

    def hoo(self):
        ...

    def __str__(self):
        return self.full_date

@dataclass
class MyDateTime:
    def __init__(self, year, month, day):
        self.year = year
        self.month = month
        self.day = day

    def foo(self):
        ...

    def goo(self):
        ...

    def hoo(self):
        ...

    def __str__(self):
        return f"{self.year}, {self.month}, {self.day}"

Refactoring:

• Introduce Null Object
• Extract Class
• Move Function

Sources

• [1] - Mika Mäntylä, "Bad Smells in Software - a Taxonomy and an Empirical Study" (2003)
• [2] - MS Haque, J Carver, T Atkison, "Causes, impacts, and detection approaches of code smell: A survey" (2018)
• [Origin] - Martin Fowler, "Refactoring: Improving the Design of Existing Code (3rd Edition)" (1999)