This article is also published on my blog.
Sometimes, you need to do more than just assign a value to a property on initialization.
class Foo {
let formatter = DateFormatter()
}
You might need to configure some of the properties. The first thing that comes to your mind is probably doing it in an initializer.
class Foo {
let formatter = DateFormatter()
init() {
formatter.dateStyle = .short
}
}
There are more ways how to configure your properties without putting the code in the initializer.
class Foo {
let formatter: DateFormatter = {
$0.dateStyle = .short
return $0
}(DateFormatter())
}
In the example above, you can see that the property Foo.formatter is constructed with a closure which takes the instance of DateFormatter as a parameter. You can do the same with initializing the DateFormatter directly in the closure:
class Foo {
let formatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .short
return formatter
}()
}
You can also use a function or a static method to construct the property.
func dateFormatter() -> DateFormatter {
let formatter = DateFormatter()
formatter.dateStyle = .short
return formatter
}
class Foo {
let formatter: DateFormatter = dateFormatter()
}
class Foo {
let formatter: DateFormatter = Foo.dateFormatter()
static func dateFormatter() -> DateFormatter {
let formatter = DateFormatter()
formatter.dateStyle = .short
return formatter
}
}
All these options work for local variables too.
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This article is also published on my blog.
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