impr: Slightly speed up adding breadcrumbs (#4984)

Slightly speed up adding breadcrumbs by only serializing the breadcrumb
once before passing it to the scope observers.

Author: philipphofmann

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Improvements
+
+- Slightly speed up adding breadcrumbs (#4984)
+
 ## 8.47.0
 
 > [!Important]

Sources/Sentry/SentryScope.m

@@ -135,8 +135,10 @@ - (void)addBreadcrumb:(SentryBreadcrumb *)crumb
 
         _currentBreadcrumbIndex = (_currentBreadcrumbIndex + 1) % _maxBreadcrumbs;
 
+        // Serializing is expensive. Only do it once.
+        NSDictionary<NSString *, id> *serializedBreadcrumb = [crumb serialize];
         for (id<SentryScopeObserver> observer in self.observers) {
-            [observer addSerializedBreadcrumb:[crumb serialize]];
+            [observer addSerializedBreadcrumb:serializedBreadcrumb];
         }
     }
 }