Objective-C Expressions for Debugging
Posted on December 1, 2011 by John Muchow in Debugging
In a previous post I wrote about preprocessor macros that provide filename, line number and function information to aid in debugging. A short example follows:
- (void)buttonPressed:(UIButton *)button { NSLog(@"\n Function: %s\n Pretty function: %s\n Line: %d\n File: %s\n Object: %@", __func__, __PRETTY_FUNCTION__, __LINE__, __FILE__, button); ... }
The output from the above:
In addition to the macros, there are four Objective-C expressions which provides additional information about the current context in your code. Three of the four expressions are shown in the example below:
- (void)buttonPressed:(UIButton *)button { NSLog(@"Current selector: %@", NSStringFromSelector(_cmd)); NSLog(@"Object class: %@", NSStringFromClass([self class])); NSLog(@"Filename: %@", [[NSString stringWithUTF8String:__FILE__] lastPathComponent]); ... }
The fourth expression available in Objective-C creates an array, where each entry is a string representing a value in the current stack trace. Here is how to print the stack trace:
NSLog(@"Stack trace: %@", [NSThread callStackSymbols]);
Related posts:
- Objective-C Comment Styles
- Resize/Scale of an Image – Take 1 – Using an Objective-C Category
- Objective-C Object as a C Structure
You can also use “po [NSThread callStackSymbols]” in the Xcode console. This is especially useful after EXE_BAD_ACCESS, SIGABRT and similar crashes that do not automatically write the call stack and exception description to the console.
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thank u!!!
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thank you ………….
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What is the +335, +71, +63 mean in the code?
Is there any way to get the line numbers or function names from the callstack??
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