Modify dates in Swift
In this post, we’ll extend Date with functions that let us add and remove seconds, minutes, hours and days to a date.
The basics
Date manipulation is a common task in many apps. For instance, we may want to know the date five hours from now, to schedule an operation, refresh or remove data etc.
Date has an easy way to do this. addingTimeInterval lets you add a TimeInterval (which is a typealias for Double) to any date and returns the resulting date.
For instance, this adds an hour to the current date:
let date = Date()
date.addingTimeInterval(3600)
However, I find addingTimeInterval cumbersome to use when you want more fine-grained control or use larger units than seconds. Also, the code isn’t that readable.
More readable extensions
We can use addingTimeInterval in a set of extension functions, to create more readable functions for manipulating dates:
public extension Date {
func adding(days: Double) -> Date {
let seconds = Double(days) * 60 * 60 * 24
return addingTimeInterval(seconds)
}
func adding(hours: Double) -> Date {
let seconds = Double(hours) * 60 * 60
return addingTimeInterval(seconds)
}
func adding(minutes: Double) -> Date {
let seconds = Double(minutes) * 60
return addingTimeInterval(seconds)
}
func adding(seconds: Double) -> Date {
addingTimeInterval(Double(seconds))
}
func removing(days: Double) -> Date {
adding(days: -days)
}
func removing(hours: Double) -> Date {
adding(hours: -hours)
}
func removing(minutes: Double) -> Date {
adding(minutes: -minutes)
}
func removing(seconds: Double) -> Date {
adding(seconds: -seconds)
}
}
If you now want to modify a certain date, you can do so with more readable code and also chain multiple operations together:
let date = Date()
.adding(days: 3)
.adding(hours: 2)
.removing(seconds: 15)
I think this is much more readable than the time interval-based function.
Source code
I have added these extensions to my SwiftKit library. You can find the source code here. Feel free to try it out and let me know what you think!