TL;DR: Use arrays for rapid prototyping, use object for serious business.
Problems
Coupling
Information Hiding
Code Duplication
Fail Fast
Integrity
Solutions
Reify objects
Create cohesive small objects
Avoid anemic objects and identify their cohesive relations.
Sample Code
Wrong
// Array with some raw data, what can go wrong?
val coordinates = arrayOf(1000.0, 2000.0)
Anemic
data class GeographicCoordinate(
val longitude: Double,
val latitude: Double
)
// An error should be thrown since these values don't exist on Earth
val coordinates = GeographicCoordinate(1000.0, 2000.0)
Validated
class GeographicCoordinate(
val longitude: Double,
val latitude: Double
) {
init {
if (!isValidLatitude(latitude))
throw InvalidLatitudeException(latitude)
if (!isValidLongitude(longitude))
throw InvalidLongitudeException(longitude)
}
private fun isValidLatitude(latitude: Double) =
latitude in -90.0..90.0
private fun isValidLongitude(longitude: Double) =
longitude in -180.0..180.0
}
// An error should be thrown since these values don't exist on Earth
val coordinates = GeographicCoordinate(1000.0, 2000.0)
Right
Degrees deserve reification...
data class Latitude(val degree: Double) {
init {
if (degree !in -90.0..90.0)
throw InvalidLatitudeException(degree)
}
}
data class Longitude(val degree: Double) {
init {
if (degree !in -180.0..180.0)
throw InvalidLongitudeException(degree)
}
}
data class GeographicCoordinate(
val longitude: Longitude,
val latitude: Latitude
)
// An error should be thrown since these values don't exist on Earth
val coordinates = GeographicCoordinate(
Longitude(1000.0),
Latitude(2000.0)
)
Many people suffer from primitive obsession and believe this is over-design. Designing software is about making decisions and comparing trade-offs. The performance argument is not valid nowadays since modern virtual machines can efficiently deal with small short-lived objects.
Conclusion
When creating objects, we must not think of them as data. This is a common misconception.
We should stay loyal to our Bijection and discover real-world objects.
Most associative arrays have cohesion and represent real-world entities, and we must treat them as first-class objects.
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