add observeFirst mode, and update doc

README.md

@@ -85,6 +85,7 @@ The library provides additional macros for finer control:
 - `@ObservableOnly`: The property is observable but not stored in `UserDefaults`.
 - `@Ignore`: The property is neither observable nor stored in `UserDefaults`.
 - `@DefaultsKey`: Specifies a custom `UserDefaults` key for the property.
+- `@DefaultsBacked`: The property is stored in `UserDefaults` and observable.
 
 #### Example
 
@@ -125,6 +126,7 @@ public init(
 - `userDefaults`: The `UserDefaults` instance to use (default is `.standard`).
 - `ignoreExternalChanges`: If `true`, the instance ignores external `UserDefaults` changes (default is `false`).
 - `prefix`: A prefix for all `UserDefaults` keys associated with this class. The prefix must not contain '.' characters.
+- `observeFirst`: Observation priority mode. When enabled (set to true), only properties explicitly marked with `@DefaultsBacked` will correspond to UserDefaults, while others will be treated as ObservableOnly. The default value is false
 
 #### Example Usage
 
@@ -196,6 +198,16 @@ struct ContentView: View {
 }
 ```
 
+## Observe First Mode
+
+You can enable this mode by setting the observeFirst parameter in the `@ObservableDefaults` macro:
+
+```swift
+@ObservableDefaults(observeFirst: true)
+```
+
+When this mode is enabled, only properties explicitly marked with `@DefaultsBacked` will be persisted to UserDefaults. All other properties will automatically have the `@ObservableOnly` macro applied, making them observable but not persisted. Think of this as the inverse of the standard mode, focusing on observability while adding persistence capabilities to individual properties as needed.
+
 ## Important Notes
 
 - **External Changes**: By default, `ObservableDefaults` instances respond to external changes in `UserDefaults`. You can disable this by setting `ignoreExternalChanges` to `true`.

Sources/ObservableDefaults/Macros.swift

@@ -37,9 +37,10 @@ public macro ObservableOnly() = #externalMacro(module: "ObservableDefaultsMacros
 // - ignoreExternalChanges: Ignore notifications from external modifications. When true, the instance will only respond to its own data modifications
 // - suiteName: The suite name for UserDefaults
 // - prefix: Prefix for UserDefaults keys. Note: It cannot contain the '.' character
+// - observeFirst: Observation priority mode. When enabled (set to true), only properties explicitly marked with `@DefaultsBacked` will correspond to UserDefaults, while others will be treated as ObservableOnly. The default value is false
 // If a parameter is set in both the macro and the initializer, the value in the initializer takes precedence
 @attached(member, names: named(_$observationRegistrar), named(_userDefaults), named(_isExternalNotificationDisabled), named(access), named(withMutation), named(getValue), named(setValue), named(UserDefaultsWrapper), named(init), named(_prefix), named(cancellables), named(setupUserDefaultsObservation),
           named(checkForChanges), named(observer), named(DefaultsObservation), named(observerStarter))
 @attached(extension, conformances: Observable)
 @attached(memberAttribute)
-public macro ObservableDefaults(autoInit: Bool = true, ignoreExternalChanges: Bool = false, suiteName: String? = nil, prefix: String? = nil) = #externalMacro(module: "ObservableDefaultsMacros", type: "ObservableDefaultsMacros")
+public macro ObservableDefaults(autoInit: Bool = true, ignoreExternalChanges: Bool = false, suiteName: String? = nil, prefix: String? = nil, observeFirst: Bool = false) = #externalMacro(module: "ObservableDefaultsMacros", type: "ObservableDefaultsMacros")

Sources/ObservableDefaultsClient/main.swift

@@ -12,11 +12,13 @@
 import Foundation
 import ObservableDefaults
 
-@ObservableDefaults
+@ObservableDefaults(observeFirst: true)
 public class Test {
     @DefaultsKey(userDefaultsKey: "firstName")
+    @DefaultsBacked
     public var name: String = "abc"
 
-    @ObservableOnly
     var age: String?
+
+    var sex: Bool = false
 }

Sources/ObservableDefaultsMacros/Macros/ObservableDefaultsMacro.swift

@@ -18,6 +18,7 @@ public enum ObservableDefaultsMacros {
     static let ignoreExternalChanges: String = "ignoreExternalChanges"
     static let suiteName: String = "suiteName"
     static let prefix: String = "prefix"
+    static let observeFirst: String = "observeFirst"
 }
 
 extension ObservableDefaultsMacros: MemberMacro {
@@ -30,7 +31,7 @@ extension ObservableDefaultsMacros: MemberMacro {
 
         let className = IdentifierPatternSyntax(identifier: .init(stringLiteral: "\(identifier.name.trimmed)"))
 
-        let (autoInit, suiteName, prefix, ignoreExternalChanges) = extractProperty(node)
+        let (autoInit, suiteName, prefix, ignoreExternalChanges, _) = extractProperty(node)
 
         // Traverse all members and get all members with isPersistent set to true
         guard let classDecl = declaration as? ClassDeclSyntax else {
@@ -189,12 +190,12 @@ extension ObservableDefaultsMacros: MemberMacro {
             }
             """
         let observerStarterSyntax: DeclSyntax =
-        """
-        private func observerStarter() {
-            observer = DefaultsObservation(host: self, userDefaults: _userDefaults, prefix: _prefix)
-        }
-        """
-        
+            """
+            private func observerStarter() {
+                observer = DefaultsObservation(host: self, userDefaults: _userDefaults, prefix: _prefix)
+            }
+            """
+
         return [
             registrarSyntax,
             accessFunctionSyntax,
@@ -228,21 +229,29 @@ extension ObservableDefaultsMacros: ExtensionMacro {
 
 extension ObservableDefaultsMacros: MemberAttributeMacro {
     public static func expansion(
-        of _: AttributeSyntax,
+        of node: AttributeSyntax,
         attachedTo _: some DeclGroupSyntax,
         providingAttributesFor member: some DeclSyntaxProtocol,
         in _: some MacroExpansionContext
     ) throws -> [SwiftSyntax.AttributeSyntax] {
+        let (_, _, _, _, observeFirst) = extractProperty(node)
         guard let varDecl = member.as(VariableDeclSyntax.self),
-              varDecl.isPersistent
+              varDecl.isObservable
         else {
             return []
         }
-        return [
-            """
-            @\(raw: DefaultsBackedMacro.name)
-            """,
-        ]
+
+        if observeFirst {
+            if !varDecl.hasAttribute(named: DefaultsBackedMacro.name) && !varDecl.hasAttribute(named: ObservableOnlyMacro.name){
+                 return [ "@\(raw: ObservableOnlyMacro.name)"]
+            }
+        } else {
+            if varDecl.isPersistent {
+                return  [ "@\(raw: DefaultsBackedMacro.name)" ]
+            }
+        }
+
+        return []
     }
 }
 
@@ -255,12 +264,14 @@ extension ObservableDefaultsMacros {
         autoInit: Bool,
         suiteName: String?,
         prefix: String?,
-        ignoreExternalChanges: Bool
+        ignoreExternalChanges: Bool,
+        observeFirst: Bool
     ) {
         var autoInit = true
         var suiteName: String?
         var prefix: String?
         var ignoreExternalChanges = false
+        var observeFirst = false
 
         if let argumentList = node.arguments?.as(LabeledExprListSyntax.self) {
             for argument in argumentList {
@@ -280,9 +291,13 @@ extension ObservableDefaultsMacros {
                           let stringLiteral = argument.expression.as(StringLiteralExprSyntax.self)
                 {
                     prefix = stringLiteral.trimmedDescription
+                } else if argument.label?.text == ObservableDefaultsMacros.observeFirst,
+                          let booleanLiteral = argument.expression.as(BooleanLiteralExprSyntax.self)
+                {
+                    observeFirst = booleanLiteral.literal.text == "true"
                 }
             }
         }
-        return (autoInit, suiteName, prefix, ignoreExternalChanges)
+        return (autoInit, suiteName, prefix, ignoreExternalChanges, observeFirst)
     }
 }