Lazy instantiation

[mikeneirinck]

In chapter 25 you use a constant defined by a closure. Consequently you leave out the lazy keyword. If it had been a property the constant would have needed a value hence it would not have been lazily instantiated. Moving it to be a global makes me wonder if it is lazily instantiated?

[syedfa]

@mikeneirinck Thanks very much for your question!

Are you referring to this block of code?

    private let dateFormatter: DateFormatter = {
         // the code that sets up the DateFormatter object
         return formatter
    }() 

If so, because the code block is a let, it cannot be lazy. You get the following compile time error:

‘lazy’ cannot be used on a ‘let’

Here is an excerpt from The Swift Book which explains why:

You must always declare a lazy property as a variable (with the var keyword), because its initial value might not be retrieved until after instance initialization completes. Constant properties must always have a value before initialization completes, and therefore cannot be declared as lazy.

I hope this helps!

All the best!

[mikeneirinck]

Sure but shouldn’t it be a lazy var?