Add another example for Macro

Author: ImaginativeShohag

README.md

@@ -124,6 +124,19 @@ Add fonts to the [project](https://github.com/ImaginativeShohag/Why-Not-SwiftUI/
 
 - `fileSize() -> Int` : The file size in KB.
 
+# Macro
+
+## Pre-built Swift macros:
+
+- `#warning("message")`
+- `#line`
+- `#function`
+- `#file`
+- `#column`
+- `#id` ... `#endif`
+- `#filePath`
+- `#colorLiteral(red: 0.292, green: 0.081, blue: 0.6, alpha: 255)`
+
 ## Licence
 
 ```

packages/SwiftMacros/Sources/CustomMacros/CustomMacros.swift

@@ -1,5 +1,5 @@
-import SwiftCompilerPlugin
 import Foundation
+import SwiftCompilerPlugin
 import SwiftSyntax
 import SwiftSyntaxBuilder
 import SwiftSyntaxMacros
@@ -28,6 +28,8 @@ public struct StringifyMacro: ExpressionMacro {
 
 // MARK: -
 
+/// Source: https://www.avanderlee.com/swift/macros/
+
 public struct URLMacro: ExpressionMacro {
     public static func expansion(
         of node: some FreestandingMacroExpansionSyntax,
@@ -83,10 +85,62 @@ enum URLMacroError: Error, CustomStringConvertible {
 
 // MARK: -
 
+/// Source: https://betterprogramming.pub/use-swift-macros-to-initialize-a-structure-516728c5fb49
+
+public struct StructInitMacro: MemberMacro {
+    public static func expansion(
+        of node: AttributeSyntax,
+        providingMembersOf declaration: some DeclGroupSyntax,
+        in context: some MacroExpansionContext
+    ) throws -> [SwiftSyntax.DeclSyntax] {
+        guard let structDecl = declaration.as(StructDeclSyntax.self) else {
+            throw StructInitError.onlyApplicableToStruct
+        }
+
+        let members = structDecl.memberBlock.members
+        let variableDecl = members.compactMap { $0.decl.as(VariableDeclSyntax.self) }
+        let variablesName = variableDecl.compactMap { $0.bindings.first?.pattern }
+        let variablesType = variableDecl.compactMap { $0.bindings.first?.typeAnnotation?.type }
+
+        let initializer = try InitializerDeclSyntax(StructInitMacro.generateInitialCode(variablesName: variablesName, variablesType: variablesType)) {
+            for name in variablesName {
+                ExprSyntax("self.\(name) = \(name)")
+            }
+        }
+
+        return [DeclSyntax(initializer)]
+    }
+
+    public static func generateInitialCode(variablesName: [PatternSyntax],
+                                           variablesType: [TypeSyntax]) -> SyntaxNodeString
+    {
+        var initialCode = "init("
+        for (name, type) in zip(variablesName, variablesType) {
+            initialCode += "\(name): \(type), "
+        }
+        initialCode = String(initialCode.dropLast(2))
+        initialCode += ")"
+        return SyntaxNodeString(stringLiteral: initialCode)
+    }
+}
+
+enum StructInitError: CustomStringConvertible, Error {
+    case onlyApplicableToStruct
+
+    var description: String {
+        switch self {
+        case .onlyApplicableToStruct: return "@StructInit can only be applied to a structure"
+        }
+    }
+}
+
+// MARK: -
+
 @main
 struct URLMacroPlugin: CompilerPlugin {
     let providingMacros: [Macro.Type] = [
         StringifyMacro.self,
         URLMacro.self,
+        StructInitMacro.self,
     ]
 }

packages/SwiftMacros/Sources/SwiftMacros/SwiftMacros.swift

@@ -12,6 +12,9 @@ import Foundation
 @freestanding(expression)
 public macro stringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "CustomMacros", type: "StringifyMacro")
 
+
+/// Source: https://www.avanderlee.com/swift/macros/
+///
 /// A macro that produces an unwrapped URL in case of a valid input URL.
 /// For example,
 ///
@@ -20,3 +23,7 @@ public macro stringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "C
 /// produces an unwrapped `URL` if the URL is valid. Otherwise, it emits a compile-time error.
 @freestanding(expression)
 public macro URL(_ stringLiteral: String) -> URL = #externalMacro(module: "CustomMacros", type: "URLMacro")
+
+/// Source: https://betterprogramming.pub/use-swift-macros-to-initialize-a-structure-516728c5fb49
+@attached(member, names: named(init))
+public macro StructInit() = #externalMacro(module: "CustomMacros", type: "StructInitMacro")

packages/SwiftMacros/Sources/SwiftMacrosClient/main.swift

@@ -6,8 +6,22 @@ let b = 25
 
 let (result, code) = #stringify(a + b)
 
+
+/// Source: https://www.avanderlee.com/swift/macros/
+
 print("The value \(result) was produced by the code \"\(code)\"")
 
 let url: URL = #URL("https://imaginativeworld.org")
 
 print("Url: \(url)")
+
+/// Source: https://betterprogramming.pub/use-swift-macros-to-initialize-a-structure-516728c5fb49
+
+@StructInit
+struct Book {
+    var id: Int
+    var title: String
+    var subtitle: String
+    var description: String
+    var author: String
+}