Xcode Tricks. ios App Development Fall 2010 Lecture 13

Transcription

1 Xcode Tricks ios App Development Fall 2010 Lecture 13

2 Questions?

3 Announcements Reminder: Assignment #3 due Monday, October 18 th by 11:59pm

4 Today s Topics Building & Running Code Troubleshooting Debugging Clang Static Analyzer Editor Shortcuts Refactoring

5 Notes I m showing the relevant portions of the view controller interfaces and implementations in these notes Remember to release relevant memory in the -dealloc methods they are not shown here You will also need to wire up outlets and actions in IB Where delegates or data sources are used, they too require wiring in IB

6 Nomenclature

7 Nomenclature Much of tonights material involves keyboard shortcuts Just to make sure that everyone is on the same, the following common symbols are used to represent the associated keys!the command key!the option key!the return key!the escape key! the control key!the shift key the arrow keys

8 Building & Running Code

9 Building & Running Most of you have probably already been using the keyboard shortcuts for building source code If not, they warrant repeating... B performs a build of the project build and run the project

10 Dealing with Errors & Warnings If we have errors in our code, these are called out to us in Xcode with messages that look like this...

11 Dealing with Errors & Warnings B brings up build results window which contains all of the messages in a single window which we can use to jump to the code associated with each method

12 Dealing with Errors & Warnings Alternatively you can use the following keyboard shortcuts to jump between the lines of code referenced by these compiler errors and warnings... = jumps forwards to the next line/message = jumps backwards to the previous line/message

13 Running Code

14 Running Code Again, I know that most of you have already been using the keyboard shortcut for running your app... R opens the console and brings it to the foreground, then you can press to build and run your app The console can get cluttered any you may wish to clear it occasionally, there are buttons on the toolbar for this, or you could use the keyboard sequence R clears the console

15 Running the Console Automatically There s also a setting under preferences which you can bring up with,

16 Troubleshooting

17 The HERE Log Message So, your app is crashing, but you re not sure exactly where You might try to see if certain code gets executed by placing adding NSLog statement Though, things tend to get lost in the mess if you have too many log statements that end up looking like this... 2"); You ll end up with something that s not really scalable :06: Foo[4654:207] HERE :06: Foo[4654:207] HERE :06: Foo[4654:207] foo

18 Slightly Improved HERE Log Message You can use some identifiers which the pre-processor replaces with data about your file For example, the following code... - (void)somemethodoranother { NSLog(@"%s:%d:%s", FILE, LINE, FUNCTION ); } Outputs the slightly more useful :08: Foo[4689:207] /Users/Dan/Desktop/Foo/Classes/ FooViewController.m:62:-[FooViewController somemethodoranother] Can quickly copy and paste as needed without having to type a bunch of log statements and change the messages

19 Using the Debugger If you find the process of using log statements tedious (edit, save, build, run, repeat), then you may wish to use the built in debugger If that s your cup of tea, you ll be glad to know that Xcode has a great debugger integrated right into Xcode

20 GDB

21 GDB Same GNU Project debugger you re accustomed to on Linux Allows you to see what is going on inside your program while it executes (or what it was doing when it crashed) GDB can do four main kinds of things... Start your app, specifying things that might affect its behavior Make your app stop on specified conditions Examine what happened, when your app has stopped Change things in your app, so you can experiment with changing the state of variables, etc.

22 Running GDB If you are used to pressing the Build button in the toolbar you can simply hold down the key while pressing the button to toggle between normal and debug modes... If your app crashes the raw GDB text interface will be in the run console You ll need to have the active configuration set to Debug This is the default unless you changed it

23 If You Take One Thing Away... If your app crashes, there s a good chance you can get a meaningful stack trace by issuing the where command... Start from the top and work your way down looking for your code

24 Basic Usage Demo For an even more details you can bring the full blown debugger using the Y shortcut

25 Basic Usage Demo Using the run/debugger console... Skip over, step into, step out of Continue Printing variables (p, po) Setting/removing breakpoints See the GDB manual for a full list of commands

26 LLVM & Clang

27

28 LLVM & Clang The Low Level Virtual Machine (LLVM) project is a next generation compilation infrastructure It s pretty clear that Apple s betting big on LLVM Phasing out GCC in favor of LLVM Clang is a compiler front-end for C, ObjC and now reasonable C++ support Utilizes LLVM for the backend Clang project also includes a static analyzer Xcode s future is moving towards a more integrated infrastructure using LLVM, Clang and LLDB (debugger)

29 Compiler Landscape GCC 4.2 Source Code Parser GCC CodeGen GCC Machine Code LLVM-GCC Source Code Parser GCC CodeGen LLVM Machine Code LLVM Compiler Source Code Parser Clang LLVM CodeGen LLVM Machine Code Adapted from WWDC 2010 Session 312 What s New in the LLVM Compiler

30 Clang Static Analyzer Think of static analysis as an advanced warnings tool that can identify bugs in your code without having to execute it Memory leaks Values never read Uninitialized variables To run the static analysis tool, you can a build and analyze using A Seems like there s a bug in Xcode (ios SDK 4.1) where it refuses to run when the target is set to Simulator Simply switch to Device to do analysis

31 Clang Static Analyzer

32 Clang Static Analyzer

33 Editor Shortcuts

34 Basic Editor Shortcuts We ve already discussed numerous basic shortcuts, such as... Pressing to bring up autocompletion Using / to jump to the next section in an autocomplete Commenting/uncommenting sections of code by first selecting them and then pressing / Switching between header and implementation files by using

35 Getting Help We ve also discussed bringing up the help documentation window using the? shortcut Additionally, we ve discussed in class using the following shortcuts which can be used from the editor window double click on a method/class in Xcode to bring up the documentation for that method/class/etc. double click on a method/class in Xcode to jump to that method/class declaration in its header

36 Editing Pane Options As you may have figured out, double clicking on a class in the Groups & Files pane will open that class in a new editor that fills the window There are also some other options for manipulating the size of the editor pane E will collapse the File Name pane causing the editor to take up the full height of the window E will collapse both the Groups & Files and File Name panes causing the editor to be full window You can repeat the shortcut to toggle back and forth

37 Folding Blocks of Code You can collapse and expand blocks of code within Xcode with a couple of shortcuts (you can also do this from the gutter to the left of the source code) collapses the current block expands the current block collapses all methods in a class expands all methods in a class There s also a mode that shades out everything but the current block that can be toggled on and off via F

38 Position Related Items L opens a dialog that lets you type in a line or column number and jump to that line of code in the current file L centers the current line in the middle of the buffer

39 Line and Column Numbering Line or column numbers can be enabled under preferences...

40 Navigating Between Files You can bring up the open files drop down with 1 Just start typing file name, then press (or use and )

41 Navigating Between Files The forward and backward arrows atop the editor act as a history of where you ve been (sort of like a web browser) Can be used to cycle between open files Can also use the and shortcuts

42 Navigating Between Files There s also a powerful open quickly window that lets you open any resource (including NIBs) directly from Xcode Use D to bring up the open quickly window Just start typing the resource name and it will list matches Use & to change files, press to open

43 Navigating Within a File Similar to the file drop down, there s also a function/method drop down that you can bring up by pressing 2

44 Navigating Within a File You may have noticed that there were also labels mixed in with the function/method names These titles are inserting a #pragma mark statement... Ignored by the compiler, but read by Xcode #pragma mark - #pragma mark Drawing Methods - (void)drawcircle {! } - (void)drawsquare {! } General form is: #pragma mark <title> (a - draws a separator) - (void)drawtriangle {! }

45 Navigating Within a File The functions/method drop down with our title and separator section...

46 Navigating Within a File In addition to the #pragma mark style notations, we can also put special comments in the code and have then show up in the functions/methods menu as well... // TODO: blah // FIXME: blah //???: label //!!!: label

47 Custom Key Bindings Xcode is very flexible and allows you to add your own new keybindings or even re-wire the existing bindings This can be configured under Preferences as well...

48 Refactoring

49 Refactor Local Variables You can chance in scope instances of a variable in a given scope by first selecting the variable, then pressing T This will draw a box around the variable and as you type, all instances of it in the scope will change...

50 Refactor Instance Variables This change in scope feature works well for local variables, but doesn t work for class level instance variables To refactor all instances of a property across a class you can use J over the property to bring up the refactoring dialog...

51 Refactor Instance Variables Renaming a property by refactoring has the added benefit that it will even go into the NIB file and make changes there Additionally, you can also preview (and approve or deny) what s going to change before Xcode actually does it

52 Refactor Classes You can also use refactoring to rename classes In this case, in addition to renaming everything in the implementation, header and NIB files Xcode will also rename the files themselves for you...

53 Refactor to Extract Code into Method We can also use the refactor command to automatically separate out a chunk of inline code to its own method Simply select the section of code and press J...

54 Refactor to Extract Code into Method This will do some analysis of the code and suggest a method signature based on what s going on in the code Here s the stubbed out method signature for our selection...

55 Refactor to Extract Code into Method We can give it a name, and preview the changes...

56 Refactor to Extract Code into Method The result of refactoring and extracting some code into a method...

57 Additional Resources Xcode Workspace Guide DeveloperTools/Conceptual/XcodeWorkspace/ Xcode Debugging Guide DeveloperTools/Conceptual/XcodeDebugging/ What's New in Xcode DeveloperTools/Conceptual/WhatsNewXcode/ WWDC 10 Session 330 Developer Tools State of the Union

58 For Next Class Location Awareness Programming Guide UserExperience/Conceptual/LocationAwarenessPG/