Debugging in Swift - Speaker Deck

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Debugging in Swift how hard can it be @_Caro _N, 22/3/2015

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Why do we struggle with debugging? @_Caro _N, 22/3/2015

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Output is not helpful (lldb) po objectiveCString 0x00007fbaa1f24910 (ObjectiveC.NSObject = {}) @_Caro _N, 22/3/2015

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Error messages make no sense @_Caro _N, 22/3/2015

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What?! That tool exists? @_Caro _N, 22/3/2015

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How debugging should be like • Get to the content of interest @_Caro _N, 22/3/2015

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How debugging should be like • Get to the content of interest • Get helpful error messages @_Caro _N, 22/3/2015

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How debugging should be like • Get to the content of interest • Get helpful error messages • Display additional information where needed @_Caro _N, 22/3/2015

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How debugging should be like • Get to the content of interest • Get helpful error messages • Display additional information where needed • Know about debugging tools @_Caro _N, 22/3/2015

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LLDB @_Caro _N, 22/3/2015

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Expression (lldb) po objectiveCString 0x00007fbaa1f24910 (ObjectiveC.NSObject = {}) @_Caro _N, 22/3/2015

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Expression (lldb) expression -O -- objectiveCString 0x00007fbaa1f24910 (ObjectiveC.NSObject = {}) @_Caro _N, 22/3/2015

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Magic command (lldb) expression -l objc -O -- (id) 0x00007fbaa1f24910 @_Caro _N, 22/3/2015

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Magic command (lldb) expression -l objc -O -- (id) 0x00007fbaa1f24910 I'm a fancy Objective-C String @_Caro _N, 22/3/2015

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Breakpoints @_Caro _N, 22/3/2015

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Editing Breakpoints @_Caro _N, 22/3/2015

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Editing Breakpoints @_Caro _N, 22/3/2015

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Editing Breakpoints @_Caro _N, 22/3/2015

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Projectwide Breakpoints • Catch Objective-C or C++ Exceptions on throw or catch @_Caro _N, 22/3/2015

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Projectwide Breakpoints • Catch Objective-C or C++ Exceptions on throw or catch @_Caro _N, 22/3/2015

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Projectwide Breakpoints • Catch Objective-C or C++ Exceptions on throw or catch • Catch OpenGL ES errors @_Caro _N, 22/3/2015

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Projectwide Breakpoints • Catch Objective-C or C++ Exceptions on throw or catch • Catch OpenGL ES errors • Stop when executing a speciﬁc function or method @_Caro _N, 22/3/2015

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Projectwide Breakpoints • Catch Objective-C or C++ Exceptions on throw or catch • Catch OpenGL ES errors • Stop when executing a speciﬁc function or method • Stop when test Assertions fail @_Caro _N, 22/3/2015

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Symbolic Breakpoints @_Caro _N, 22/3/2015

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Symbolic Breakpoints @_Caro _N, 22/3/2015

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Compiler errors @_Caro _N, 22/3/2015

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Approach? @_Caro _N, 22/3/2015

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1. Remove variables @_Caro _N, 22/3/2015

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2. Split instructions @_Caro _N, 22/3/2015

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Add return type @_Caro _N, 22/3/2015

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Launch arguments @_Caro _N, 22/3/2015

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Adding arguments in the scheme editor @_Caro _N, 22/3/2015

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Concurrency -com.apple.CoreData.ConcurrencyDebug 1 @_Caro _N, 22/3/2015

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SQL Statements -com.apple.CoreData.SQLDebug 3 @_Caro _N, 22/3/2015

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Many more -com.apple.CoreData.MigrationDebug -com.apple.CoreData.SQLiteDebugSynchronous [0,1,2] -com.apple.CoreData.SQLiteIntegrityCheck 1 -com.apple.CoreData.ThreadingDebug [1,2,3] http://matthewmorey.com/tools-for-core-data/ @_Caro _N, 22/3/2015

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Localization • -NSDoubleLocalizedStrings 1 @_Caro _N, 22/3/2015

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Localization • -NSDoubleLocalizedStrings 1 • -NSShowNonLocalizedStrings 1 @_Caro _N, 22/3/2015

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Localization • -NSDoubleLocalizedStrings 1 • -NSShowNonLocalizedStrings 1 • -AppleLanguages (es de) Technical Note TN2239 iOS Debugging Magic @_Caro _N, 22/3/2015

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Debugging tools @_Caro _N, 22/3/2015

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Charles • Debug http/https requests • Throttle trafﬁc • Record download statistics @_Caro _N, 22/3/2015

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Swift REPL • Test and interact with your app • Add new code • Clean slate xcrun swift in the terminal @_Caro _N, 22/3/2015

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Activity Tracing Trace crashes in asynchonous code os_activity_t activity = os_activity_start("activity name", OS_ACTIVITY_FLAG_DEFAULT); // [...] os_activity_set_breadcrumb("event description"); // [...] os_trace("Received %d creates, %d updates, %d deletes", created, updated, deleted); // [...] os_activity_end(activity); @_Caro _N, 22/3/2015

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Activity Tracing @_Caro _N, 22/3/2015

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Activity Tracing http://www.objc.io/issue-19/activity-tracing.html @_Caro _N, 22/3/2015

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Summary • expression -l objc -O -- (id) 0x00007fbaa1f24910 • Edit Breakpoints, add symbolic and exception breakpoints • Tackle incomprehensive compiler errors • Launch arguments • Charles, REPL, Activity tracing @_Caro _N, 22/3/2015

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Thanks @_Caro _N, 22/3/2015