Swift Language Variables & Properties Lazy Stored Properties
Example
Lazy stored properties have values that are not calculated until first accessed. This is useful for memory saving when the variable's calculation is computationally expensive. You declare a lazy property with lazy:
lazy var veryExpensiveVariable = expensiveMethod()
Often it is assigned to a return value of a closure:
lazy var veryExpensiveString = { () -> String in
var str = expensiveStrFetch()
str.expensiveManipulation(integer: arc4random_uniform(5))
return str
}()
Lazy stored properties must be declared with var.
