[iOS] Clarify thread-safety for MARewardedAd.isReady / MAInterstitialAd.isReady (possible data race)

[maximkir-fl]

isReady is frequently consulted from non-main actors/threads (for example, inside Swift-Concurrency code).
Because the AppLovin SDK updates its internal state on the main thread (delegate callbacks),
reading isReady off the main thread creates a data race that can cause false negatives.
In production, we observe time-out warnings like

Timeout expired, ad not ready for adUnitId: XXXXXX

even though the ad finished loading seconds earlier.

---

Repro project

1. Create a small Swift app:

   let ad = MARewardedAd.shared(withAdUnitIdentifier: "«TEST_AD_UNIT»")
   ad.delegate = self
   ad.loadAd()
   
   Task.detached {               // background executor
       while true {
           print("isReady:", ad.isReady)
           try? await Task.sleep(nanoseconds: 50_000_000)   // 50 ms
       }
   }

2. Observe console output right after didLoad fires on the main thread:
   isReady prints false for several iterations before flipping to true
   (sometimes it never flips).

---

Expected behaviour

• Either
– Accessing isReady from any thread/actor is documented as unsafe,
or
– The property is made thread-safe / @MainActor-isolated so that mixed-thread
access is benign.

---

Actual behaviour

Reading from non-main threads sometimes returns stale false, which makes
apps implement unnecessary retry/timeout logic and degrades UX.

---

Environment

• AppLovin MAX SDK version: 13.0.0
• Xcode version: 16.4
• iOS deployment target: 15
• Device / OS: occurs on both Simulator and Device (iOS 17–18)

---

Proposed solutions

1. Document clearly (in headers & guides) that all MAX API calls must occur on the main thread / @MainActor.

2. Objective-C header enforcement

   #define MA_REQUIRES_MAIN_THREAD  __attribute__((objc_requires_main_queue))
   
   @property (nonatomic, assign, readonly, getter=isReady) BOOL ready MA_REQUIRES_MAIN_THREAD;

3. Swift overlay

   @MainActor public var isReady: Bool { get }

4. Swift-6–readiness (delegate protocols)
   Swift 6 ships with Strict Concurrency enabled; compiling the current SDK
   with -warn-concurrency emits hundreds of warnings.
   Please mark every delegate protocol as @MainActor and, where applicable,
   wrap Obj-C protocols with a Swift overlay:

   /// Always invoked on the main thread.
   @protocol MARewardedAdDelegate <MAAdDelegate>
   - (void)didLoadAd:(MAAd *)ad;
   …
   @end

   @MainActor
   public protocol MARewardedAdDelegate: MAAdDelegate {
       func didLoad(_ ad: MAAd)
       …
   }

   The same applies to
   • MAInterstitialAdDelegate
   • MABannerAdDelegate
   • any other MAX delegate that is guaranteed to run on the main queue.

These changes will eliminate the current data race, silence Swift-6
concurrency warnings, and give developers compile-time guarantees about thread
safety.

[applovinAsh]

Hi @maximkir-fl, can you provide more information, such as how you confirm that the ad is ready before isReady is set to true?

I tested with similar code and see that isReady is true when the SDK marks it as ready with no delay. Where are you checking if the ad is ready?