From 33e1c24f58ebc4e2459a951245219c081dfe44a2 Mon Sep 17 00:00:00 2001
From: Hwee-Boon Yar <hboon@motionobj.com>
Date: Wed, 9 May 2018 01:11:32 +0800
Subject: [PATCH] Fix: crash on iPhone X while fetching transactions in
 background. Part of upstream commit 61ec7a4405578e3042db64469cf85ca259b85f69

---
 .../TransactionDataCoordinator.swift          | 29 +++++++++++++++----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/Trust/Transactions/Coordinators/TransactionDataCoordinator.swift b/Trust/Transactions/Coordinators/TransactionDataCoordinator.swift
index cb36a1355..92994e478 100644
--- a/Trust/Transactions/Coordinators/TransactionDataCoordinator.swift
+++ b/Trust/Transactions/Coordinators/TransactionDataCoordinator.swift
@@ -45,20 +45,39 @@ class TransactionDataCoordinator {
     ) {
         self.session = session
         self.storage = storage
+        NotificationCenter.default.addObserver(self, selector: #selector(stopTimers), name: .UIApplicationWillResignActive, object: nil)
+        NotificationCenter.default.addObserver(self, selector: #selector(restartTimers), name: .UIApplicationDidBecomeActive, object: nil)
     }
 
     func start() {
+        runScheduledTimers()
+        // Start fetching all transactions process.
+        if transactionsTracker.fetchingState != .done {
+            initialFetch(for: session.account.address, page: 0) { _ in }
+        }
+    }
+
+    @objc func stopTimers() {
+        timer?.invalidate()
+        timer = nil
+        updateTransactionsTimer?.invalidate()
+        updateTransactionsTimer = nil
+    }
+
+    @objc func restartTimers() {
+        runScheduledTimers()
+    }
+
+    private func runScheduledTimers() {
+        guard timer == nil, updateTransactionsTimer == nil else {
+            return
+        }
         timer = Timer.scheduledTimer(timeInterval: 5, target: BlockOperation { [weak self] in
             self?.fetchPending()
         }, selector: #selector(Operation.main), userInfo: nil, repeats: true)
         updateTransactionsTimer = Timer.scheduledTimer(timeInterval: 15, target: BlockOperation { [weak self] in
             self?.fetchTransactions()
         }, selector: #selector(Operation.main), userInfo: nil, repeats: true)
-
-        // Start fetching all transactions process.
-        if transactionsTracker.fetchingState != .done {
-            initialFetch(for: session.account.address, page: 0) { _ in }
-        }
     }
 
     func fetch() {