NSLog the method name with Objective-C in iPhone

Question

Currently, we are defining ourselves an extended log mechanism to print out the class name and the source line number of the log.

#define NCLog(s, ...) NSLo         


        

Answer 1

In Swift 4:

func test(){

print(#function)

}

test() //print the value "test()"

Answer 2

tl;dr

NSLog( @"ERROR %@ METHOD %s:%d ", @"DescriptionGoesHere", __func__, __LINE__ );

Details

Apple has a Technical Q&A page: QA1669 - How can I add context information - such as the current method or line number - to my logging statements?

To assist with logging:

• The C preprocessor provides a few macros.
• Objective-C provides expressions (methods).
  • Pass the implicit argument for the current method's selector: _cmd

As other answers indicated, to merely get the current method's name, call:

NSStringFromSelector(_cmd)

To get the current method name and current line number, use these two macros __func__ and __LINE__ as seen here:

NSLog(@"%s:%d someObject=%@", __func__, __LINE__, someObject);

Another example… Snippets of code I keep in Xcode's Code Snippet Library:

NSLog( @"ERROR %@ METHOD %s:%d ", @"DescriptionGoesHere", __func__, __LINE__ );

…and TRACE instead of ERROR…

NSLog( @"TRACE %@ METHOD %s:%d ", @"DescriptionGoesHere", __func__, __LINE__ );

…and a longer one using a soft-coded description passing a value ([rows count])…

NSLog( @"TRACE %@ METHOD %s:%d.", [NSString stringWithFormat:@"'Table of Contents.txt' file's count of Linefeed-delimited rows: %u.", [rows count]] , __func__, __LINE__ );

Preprocessor macros for logging

Note the use of a pair of underscore characters around both sides of the macro.

| Macro                | Format   | Description
  __func__               %s         Current function signature
  __LINE__               %d         Current line number
  __FILE__               %s         Full path to source file
  __PRETTY_FUNCTION__    %s         Like __func__, but includes verbose
                                    type information in C++ code. 

Expressions for logging

| Expression                       | Format   | Description
  NSStringFromSelector(_cmd)         %@         Name of the current selector
  NSStringFromClass([self class])    %@         Current object's class name
  [[NSString                         %@         Source code file name
    stringWithUTF8String:__FILE__]   
    lastPathComponent] 
  [NSThread callStackSymbols]        %@         NSArray of stack trace

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Logging Frameworks

Some logging frameworks may help with getting current method or line number as well. I'm not sure, as I've used a great logging framework in Java (SLF4J + LogBack) but not Cocoa.

See this question for links to various Cocoa logging frameworks.

Name of Selector

If you have a Selector variable (a SEL), you can print its method name ("message") in either of two ways as described by this Codec blog post:

• Using Objective-C call to NSStringFromSelector:
  NSLog(@"%@", NSStringFromSelector(selector) );
• Using straight C:
  NSLog(@"%s", selector );

---

This information drawn from the linked Apple doc page as of 2013-07-19. That page had been last updated 2011-10-04.

Answer 3

It's actually just as simple as:

printf(_cmd);

For some reason iOS allows _cmd to be passed as a literal char with not even a compile warning. Who knows

Answer 4

To technically answer your question, you want:

NSLog(@"<%@:%@:%d>", NSStringFromClass([self class]), NSStringFromSelector(_cmd), __LINE__);

Or you could also do:

NSLog(@"%s", __PRETTY_FUNCTION__);

Answer 5

NSLog(@"%@", NSStringFromSelector(_cmd)); // Objective-C
print(__FUNCTION__) // Swift

Answer 6

print(__FUNCTION__) // Swift
NSLog(@"%@", NSStringFromSelector(_cmd)); // Objective-C

Swift 3 and above

print(#function)