Fixes the PurchasesDelegate being deallocated on iOS

core/src/commonMain/kotlin/com/revenuecat/purchases/kmp/Purchases.kt

@@ -107,6 +107,10 @@ public expect class Purchases {
     /**
      * The delegate is responsible for handling promotional product purchases (App Store only) and
      * changes to customer information.
+     *
+     * **Note:** If your delegate is not a singleton, make sure you set this back to null when
+     * you're done to avoid memory leaks. For instance, if your delegate is tied to a screen, set
+     * this to null when the user navigates away from the screen.
      */
     public var delegate: PurchasesDelegate?
 

core/src/iosMain/kotlin/com/revenuecat/purchases/kmp/Purchases.ios.kt

@@ -119,7 +119,7 @@ public actual class Purchases private constructor(private val iosPurchases: IosP
 
     public actual var delegate: PurchasesDelegate?
         get() = iosPurchases.delegate()?.toPurchasesDelegate()
-        set(value) = iosPurchases.setDelegate(value?.toRcPurchasesDelegate())
+        set(value) = iosPurchases.setDelegate(value.toRcPurchasesDelegate())
 
     public actual val isAnonymous: Boolean
         get() = iosPurchases.isAnonymous()

core/src/iosMain/kotlin/com/revenuecat/purchases/kmp/PurchasesDelegate.ios.kt

@@ -15,8 +15,9 @@ import platform.darwin.NSObject
 internal fun RCPurchasesDelegateProtocol.toPurchasesDelegate(): PurchasesDelegate =
     (this as PurchasesDelegateWrapper).wrapped
 
-internal fun PurchasesDelegate.toRcPurchasesDelegate(): RCPurchasesDelegateProtocol =
-    PurchasesDelegateWrapper(this)
+internal fun PurchasesDelegate?.toRcPurchasesDelegate(): RCPurchasesDelegateProtocol? =
+    this?.let { PurchasesDelegateWrapper(it) }
+        .also { PurchasesDelegateStrongReference.delegate = it }
 
 private class PurchasesDelegateWrapper(val wrapped: PurchasesDelegate) :
     RCPurchasesDelegateProtocol,
@@ -45,3 +46,20 @@ private class PurchasesDelegateWrapper(val wrapped: PurchasesDelegate) :
     }
 
 }
+
+/**
+ * On the iOS platform side, the backing field of `Purchases.delegate`, `Purchases.privateDelegate`,
+ * is a `weak var`. On the multiplatform side, we wrap the actual delegate in
+ * `PurchasesDelegateWrapper` to conform to `RCPurchasesDelegateProtocol`. Since that is a private
+ * implementation detail, the only reference held to our wrapper is the `weak var`. This means that
+ * it gets deallocated the first chance it gets. For this reason, we keep a strong reference to our
+ * `PurchasesDelegateWrapper` here. This matches the Android behavior, which keeps a strong
+ * reference on the platform side already.
+ *
+ * **Note**: we cannot make our `PurchasesDelegateWrapper` an `object` directly, as objects cannot
+ * extend `NSObject`. See also
+ * [KT67930](https://youtrack.jetbrains.com/issue/KT-67930/Getting-Crash-while-building-KMM-project-with-XCode-15.3#focus=Comments-27-9796215.0-0)
+ */
+private object PurchasesDelegateStrongReference {
+    var delegate: RCPurchasesDelegateProtocol? = null
+}