rougeware/swift-lazy-containers

A few ways to have a lazily-initialized value in Swift 5.1. Note that, if you are OK with the behavior of Swift's lazy keyword, you should use that. This is for those who want very specific behaviors:

`Lazy` ##

The simple usage of this is very straightforward:


@Lazy
var myLazyString = "Hello, lazy!"

print(myLazyString) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString) // Just returns the value "Hello, lazy!"

myLazyString = "Overwritten"
print(myLazyString) // Just returns the value "Overwritten"
print(myLazyString) // Just returns the value "Overwritten"

This will print:

Hello, lazy!
Hello, lazy!
Overwritten
Overwritten

More complex initializer ##

If you have complex initializer logic, you can pass that to the property wrapper:


func makeLazyString() -> String {
    print("Initializer side-effect")
    return "Hello, lazy!"
}

@Lazy(initializer: makeLazyString)
var myLazyString: String

print(myLazyString) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString) // Just returns the value "Hello, lazy!"

myLazyString = "Overwritten"
print(myLazyString) // Just returns the value "Overwritten"
print(myLazyString) // Just returns the value "Overwritten"

You can also use it directly (instaed of as a property wrapper):

var myLazyString = Lazy<String>() {
    print("Initializer side-effect")
    return "Hello, lazy!"
}

print(myLazyString.wrappedValue) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString.wrappedValue) // Just returns the value "Hello, lazy!"

myLazyString.wrappedValue = "Overwritten"
print(myLazyString.wrappedValue) // Just returns the value "Overwritten"
print(myLazyString.wrappedValue) // Just returns the value "Overwritten"

These will both print:

Initializer side-effect
Hello, lazy!
Hello, lazy!
Overwritten
Overwritten

`ResettableLazy` ##

The simple usage of this is very straightforward:


@ResettableLazy
var myLazyString = "Hello, lazy!"

print(myLazyString) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString) // Just returns the value "Hello, lazy!"

_myLazyString.clear()
print(myLazyString) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString) // Just returns the value "Hello, lazy!"

myLazyString = "Overwritten"
print(myLazyString) // Just returns the value "Overwritten"
_myLazyString.clear()
print(myLazyString.wrappedValue) // Initializes, caches, and returns the value  "Hello, lazy!"

This will print:

Hello, lazy!
Hello, lazy!
Hello, lazy!
Hello, lazy!
Overwritten
Hello, lazy!

More complex initializer ##

If you have complex initializer logic, you can pass that to the property wrapper:


func makeLazyString() -> String {
    print("Initializer side-effect")
    return "Hello, lazy!"
}

@ResettableLazy(initializer: makeLazyString)
var myLazyString: String

print(myLazyString) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString) // Just returns the value "Hello, lazy!"

_myLazyString.clear()
print(myLazyString) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString) // Just returns the value "Hello, lazy!"

myLazyString = "Overwritten"
print(myLazyString) // Just returns the value "Overwritten"
_myLazyString.clear()
print(myLazyString.wrappedValue) // Initializes, caches, and returns the value  "Hello, lazy!"

You can also use it directly (instaed of as a property wrapper):

var myLazyString = ResettableLazy<String>() {
    print("Initializer side-effect")
    return "Hello, lazy!"
}

print(myLazyString.wrappedValue) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString.wrappedValue) // Just returns the value "Hello, lazy!"

myLazyString.clear()
print(myLazyString.wrappedValue) // Initializes, caches, and returns the value "Hello, lazy!"
print(myLazyString.wrappedValue) // Just returns the value "Hello, lazy!"

myLazyString.wrappedValue = "Overwritten"
print(myLazyString.wrappedValue) // Just returns the value "Overwritten"
_myLazyString.clear()
print(myLazyString.wrappedValue) // Initializes, caches, and returns the value  "Hello, lazy!"

These will both print:

Initializer side-effect
Hello, lazy!
Hello, lazy!
Initializer side-effect
Hello, lazy!
Hello, lazy!
Overwritten
Initializer side-effect
Hello, lazy!

`FunctionalLazy` ##

This is functionally <sub>(ha!)</sub> the same as Lazy. The only difference is I thought it'd be fun to implement it with functions instead of enums. 🤓

Package Metadata

Repository: rougeware/swift-lazy-containers

Default branch: master

README: README.md