From date should be lower than to date
TL;DR: Intervals are there. Why use plain dates?
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Missing abstraction
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Not enforced invariants
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Primitive Obsession
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Bijection Fault
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Fail Fast principle violation
- Create and use an Interval Object
The restriction "From date should be lower than to date" means that the starting date of a certain interval should occur before the ending date of the same interval.
The "From date" should be a date that comes earlier in time than the "To date".
This restriction is in place to ensure that the interval being defined makes logical sense and that the dates used to define it are in the correct order.
We all know it. But we miss creating the Interval object.
Would you create a Date as a pair of 3 Integer numbers? Certainly, not.
This is the same.
val from = LocalDate.of(2018, 12, 9)
val to = LocalDate.of(2022, 12, 22)
val elapsed = elapsedDays(from, to)
fun elapsedDays(fromDate: LocalDate, toDate: LocalDate): Long {
return ChronoUnit.DAYS.between(fromDate, toDate)
}
// You need to apply this short function
// or the inline version many times in your code
// You don't check fromDate to be less than toDate
// You can make accounting numbers with a negative number// You reify the Interval Concept
data class Interval(val fromDate: LocalDate, val toDate: LocalDate) {
init {
if (fromDate >= toDate) {
throw IllegalArgumentException(
"From date must be before to date")
}
// Of course the Interval must be immutable
// By using the keyword 'data'
}
fun elapsedDays(): Long {
return ChronoUnit.DAYS.between(fromDate, toDate)
}
}
val from = LocalDate.of(2018, 12, 9)
val to = LocalDate.of(2002, 12, 22)
val interval = Interval(from, to) // Invalid[X] Manual
This is a primitive obsession smell.
It is related to how we model things.
- Primitive
If you find software with missing simple validations, it certainly needs reification.
Code Smell 177 - Missing Small Objects
Code Smell 122 - Primitive Obsession
Code Smells are just my opinion.
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This article is part of the CodeSmell Series.