Awesome
@Buildable
Swift Macro
@Buildable
is an attached swift macro for structs, classes and enums, which produces a peer struct implementing the builder pattern. Initialise your object with minimal effort using default values.
import Buildable
@Buildable
struct Person {
let name: String
let age: Int
}
let person = PersonBuilder(age: 42).build()
Important! <br>- This macro is intended to be used for simple structs, enums and classes (see below limitations) <br>- Please report any issues you might encounter <br>- Please star this repository, if your project makes use of it :)
Table of Contents
- Detailed Example with generated builder
- Installation
- Motivation
- Limitations
- Builder default values
- Roadmap
Detailed Example with generated builder
import Buildable
@Buildable
struct Person {
let name: String
let age: Int
let address: Address
let hobby: String?
let favouriteSeason: Season
var likesReading: Bool {
hobby == "Reading"
}
static let minimumAge = 21
}
@Buildable
enum Season {
case .winter
case .spring
case .summer
case .autumn
}
@Buildable
class AppState {
let persons: [Person]
init(
persons: [Person]
) {
self.person = person
}
}
let anyPerson = PersonBuilder().build()
let max = PersonBuilder(name: "Max", favouriteSeason: .summer).build()
let appState = AppStateBuilder(persons: [max]).build()
Expanded macro
struct PersonBuilder {
var name: String = ""
var age: Int = 0
var address: Address = AddressBuilder().build()
var hobby: String?
var favouriteSeason: SeasonBuilder = SeasonBuilder().build()
func build() -> Person {
return Person(
name: name,
age: age,
address: address,
hobby: hobby,
favouriteSeason: favouriteSeason
)
}
}
struct SeasonBuilder {
var value: Season = .spring
func build() -> Season {
return value
}
}
struct AppStateBuilder {
var persons: [Person] = []
func build() -> AppState {
return AppState(
persons: persons
)
}
}
Installation
The library can be installed using Swift Package Manager.
Limitations
- The macro only works on
struct
,enum
andclass
definitions - The list of default values is limited to the values specified in the below table. All other types will require another builder to be defined
- If a builder for a specific declaration can not be generated, you can always choose to create it yourself by following the below builder naming pattern:
struct <MyType>Builder { func build() -> <MyType> { return ... } }
- If a class or a struct has one or more initialisers, the macro will use the first/top one
- For structs without an initialiser, the macro makes a best guess to decide how the implicit memberwise initializer could look like. This best guess might fail for declarations that have not been considered during implementation of the macro
- As of Swift 5.10 (01.08.2024) it is not possible to use the generated builders inside the SwiftUI
#Preview
closure
Builder default values
The list of default values is limited to the values specified in the below table.
If a type e.x. UnknownType
is not part of the list, the macro will set the default value to UnknownTypeBuilder().build()
,
assuming that the UnknownTypeBuilder
was created somewhere else.
Type | Default Value |
---|---|
UnknownType | UnknownTypeBuilder().build() |
String | "" |
Int | 0 |
Bool | false |
Double | 0 |
Float | 0 |
Date | Date() |
UUID | UUID() |
[Any] | [] |
[Any:Any] | [:] |
Any? | (implicitly nil) |
Any! | (implicitly nil) |
() -> Void | {} |
(Any) -> Void | { _ in } |
(Any, Any) -> Void | { _, _ in } |
Int8 | 0 |
Int16 | 0 |
Int32 | 0 |
Int46 | 0 |
UInt | 0 |
UInt8 | 0 |
UInt16 | 0 |
UInt32 | 0 |
UInt46 | 0 |
Data | Data() |
URL | URL(string: "https://www.google.com")! |
CGFloat | 0 |
CGPoint | CGPoint() |
CGRect | CGRect() |
CGSize | CGSize() |
CGVector | CGVector() |
Roadmap
The @Buildable
macro was created out of personal interest to reduce repetitive code in my own projects. I might continue developing the macro depending use cases I stumble across, though, I do not guarantee to keep the project up to date myself. Please create GitHub issues for any feature or bugfix you would like to see within the macro. Contributions or fixes from the Community are most welcome.