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Comment Out Large Blocks of Code with Nested Comments
Posted on March 18, 2010 by John Muchow in C
In working with a large chunk of code recently, I needed to comment out a sizeable block to verify something was working as expected. My first thought was to simply to embed the offending code within /* and */
/*
// Detect touch anywhere
UITouch *touch = [touches anyObject];
// Where is the point touched
CGPoint point = [touch locationInView:self.view];
NSLog(@"pointx: %f pointy:%f", point.x, point.y);
// Was a tab touched, if so, which one...
if (CGRectContainsPoint(CGRectMake(1, 440, 106, 40), point))
NSLog(@"tab 1 touched");
else if (...)
... more code here
else if (...)
... more code here
*/This approach works well, with one exception, nested comments in the form of /* … */ will generate a compiler error, see lines 9 – 10 below:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | /* // Detect touch anywhere UITouch *touch = [touches anyObject]; // Where is the point touched CGPoint point = [touch locationInView:self.view]; NSLog(@"pointx: %f pointy:%f", point.x, point.y); /* If you have an embedded comment in this style, you will get a compiler error */ if (CGRectContainsPoint(CGRectMake(1, 440, 106, 40), point)) NSLog(@"tab 1 touched"); else if (...) ... more code here else if (...) ... more code here */ |
To get around the problem with embedded comments, you can try this approach:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | #if 0 // Detect touch anywhere UITouch *touch = [touches anyObject]; // Where is the point touched CGPoint point = [touch locationInView:self.view]; NSLog(@"pointx: %f pointy:%f", point.x, point.y); /* If you have an embedded comment in this style, you will get a compiler error */ if (CGRectContainsPoint(CGRectMake(1, 440, 106, 40), point)) NSLog(@"tab 1 touched"); else if (...) ... more code here else if (...) ... more code here #endif |
Another option that is a little more descriptive:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | #ifdef VISIBLE // Detect touch anywhere UITouch *touch = [touches anyObject]; // Where is the point touched CGPoint point = [touch locationInView:self.view]; NSLog(@"pointx: %f pointy:%f", point.x, point.y); /* If you have an embedded comment in this style, you will get a compiler error */ if (CGRectContainsPoint(CGRectMake(1, 440, 106, 40), point)) NSLog(@"tab 1 touched"); else if (...) ... more code here else if (...) ... more code here #endif |
This approach provides a means to quickly comment in/out any number of code blocks by simply modifying a compiler directive as shown here:
// Code above will be compiled // Change to INVISIBLE and code will ~not~ be compiled #define VISIBLE
I’ve found occasion to do something like this:
// defined in some common file for use in all modules
#ifdef DEBUG_BUILD
#define IGNORE_IN_DEBUG (0) // will cause the code to be ignored in debug build
#else
#define IGNORE_IN_DEBUG (1/0) // will cause a divide by zero error in a non-debug build
#endif
// to bracket the code you want to omit
#if IGNORE_IN_DEBUG
#endif
That encourages you to clean it up before progressing to a release build, assuming that you do release builds only rarely.
Alternatively/in addition, you could probably add a build step that looks for that symbol and issues a warning if it’s found. I’m not much of an expert on build customization, though, so maybe not.
[Reply]
Don’t forget for quick commenting a selected section in Xcode. Command-/
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