Filter alerts before fetching extended info.

1Weather/Network/Notifications/NWSAlertsManager.swift

@@ -157,12 +157,12 @@ public class NWSAlertsManager {
     private func fetchAllExtendedInfo(for alerts: [NWSAlert]) {
         internalQueue.addOperation { [weak self] in
             guard let self = self else { return }
-            
-            var newAlertsToFetch = [NWSAlert]()
-            
+            let localExtendedInfoBeingFetched = self.extendedInfoBeingFetched
+            let alertsToFetch = alerts.filter { (alert: NWSAlert) -> Bool in
+                alert.extendedInfo == nil && !localExtendedInfoBeingFetched.contains(alert)
+            }
             let parser = NWSAlertInfoParser()
-            for alert in alerts.filter({ $0.extendedInfo == nil }) {
-                if !self.extendedInfoBeingFetched.contains(alert) {
+            for alert in alertsToFetch {
                 self.extendedInfoBeingFetched.insert(alert)
                 parser.fetchExtendedInfo(for: alert) { [weak self] (weatherMessage, extendedInfo) in
                     DispatchQueue.main.async { [weak self] in
@@ -181,7 +181,6 @@ public class NWSAlertsManager {
             }
         }
     }
-    }
     
     private func merge(alerts newAlerts: [NWSAlert]) {
         //TODO: optimize