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Using Instruments to Find Hangs in Your App
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If you find your app becomes unresponsive at times, it can be frustrating to find the cause. Instruments includes a Hangs instrument that reports hangs to help you find and fix hangs. This article shows you how to use the Hangs and Time Profiler instruments to find hangs and find the code causing the hangs. Profiling Your AppIn Xcode press Cmd-I to build and profile your app with Instruments. When Instruments launches, it will ask you to choose a template for profiling. Select the Time Profiler template and click the Choose button. A configuration window will open. You can choose the severity level of hangs that Instruments reports. Selecting the Include All Potential Interaction Delays will show the most hangs. Click the Record button at the top of the window to start profiling your app. Run your app. Click the Stop button when you are finished. Reading the ResultsThe Hangs instrument initially shows a summary table of the hangs it found. There is a row for each hang type. Hangs are the most severe, followed by microhangs, brief unresponsiveness, and potential interaction delays. For each hang type Instruments tells you the number of hangs along with the minimum, maximum, and average durations. Pressing Cmd-2 will show a table listing each hang. Finding the Code Causing the HangIf you find hangs in your app, you want to find the code causing the hang. The Hangs instrument won't help, but the Time Profiler instrument will. Start by creating an inspection range to focus on a hang. Above the statistics is a list of instruments. Select the Hangs instrument. There will be a graph that looks similar to the following image: There is a bar in the graph for each hang. Click inside the graph at the start of a hang. Drag to the end of the hang to set the inspection range. After setting the inspection range, select the Time Profiler instrument from the list of instruments. To see your code in the call tree view, take the following steps:
Look for any functions that have a high Self Weight value. Double-click a function to show the source code for that function and see the lines of code where your app spends the most time. Read the following article to learn more about the Time Profiler instrument:
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Swift Dev Journal
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