How to print Boolean flag in NSLog?

Question

Is there a way to print value of Boolean flag in NSLog?

BoltClock · Accepted Answer · 2014-09-10T04:10:42.877

520

Here's how I do it:

BOOL flag = YES;
NSLog(flag ? @"Yes" : @"No");

?: is the ternary conditional operator of the form:

condition ? result_if_true : result_if_false

Substitute actual log strings accordingly where appropriate.

edited Sep 10 '14 at 04:10

answered Jun 15 '11 at 13:24

BoltClock

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Easy to make this a macro, too: `#define StringFromBOOL(b) ((b) ? @"YES" : @"NO")` – jscs Jun 15 '11 at 18:36
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How does this have so many votes? This is NOT how to log a boolean value, this is how to log different values depending on a boolean value. – Acey Oct 29 '14 at 02:45
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@Acey: Apparently, people (including the original asker) were more interested in the latter. If I were to hazard a guess, it's because printing the value directly (0/1) isn't very meaningful. – BoltClock Nov 23 '14 at 06:27
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@BoltClock 0/1 isn't meaningful in log output? I thought we were all programmers here lol – Cbas Apr 03 '16 at 21:04

score 326 · Answer 2 · edited Sep 11 '14 at 06:03

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%d, 0 is FALSE, 1 is TRUE.

BOOL b; 
NSLog(@"Bool value: %d",b);

or

NSLog(@"bool %s", b ? "true" : "false");

On the bases of data type %@ changes as follows

For Strings you use %@
For int  you use %i
For float and double you use %f

edited Sep 11 '14 at 06:03

Kevin

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answered Jun 15 '11 at 13:28

SashaQbl

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score 18 · Answer 3 · answered Jun 15 '11 at 13:34

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Booleans are nothing but integers only, they are just type casted values like...

typedef signed char     BOOL; 

#define YES (BOOL)1
#define NO (BOOL)0

BOOL value = YES; 
NSLog(@"Bool value: %d",value);

If output is 1,YES otherwise NO

answered Jun 15 '11 at 13:34

Chandan Shetty SP

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No, bool is `signed char`. Your expression could potentially evaluate incorrectly if a value other than 0 or 1 is supplied. – CodaFi Jun 03 '12 at 05:30
No, the type of BOOL depends on your compiler (32 vs 64 bit), and is often not the same type as bool. bool, on the other hand, is bool, which is a standard type, and not the same as signed char. – gnasher729 May 06 '15 at 17:48

score 14 · Answer 4 · answered Aug 28 '14 at 15:58

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Note that in Swift, you can just do

let testBool: Bool = true
NSLog("testBool = %@", testBool.description)

This will log testBool = true

answered Aug 28 '14 at 15:58

arcticmatt

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In Swift you can just use `print()`. – Dmitry Aug 03 '19 at 23:03

xizor · Answer 5 · 2016-01-14T17:56:55.810

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While this is not a direct answer to Devang's question I believe that the below macro can be very helpful to people looking to log BOOLs. This will log out the value of the bool as well as automatically labeling it with the name of the variable.

#define LogBool(BOOLVARIABLE) NSLog(@"%s: %@",#BOOLVARIABLE, BOOLVARIABLE ? @"YES" : @"NO" )

BOOL success = NO;
LogBool(success); // Prints out 'success: NO' to the console

success = YES;
LogBool(success); // Prints out 'success: YES' to the console

edited Jan 14 '16 at 17:56

answered Aug 02 '13 at 14:12

xizor

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A useful macro, especially with the trick of displaying the variable name. Personally I would not use BOOL as a parameter name to avoid confusion. – jk7 Jan 13 '16 at 17:34

score 7 · Answer 6 · answered Feb 06 '13 at 22:17

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Apple's FixIt supplied %hhd, which correctly gave me the value of my BOOL.

answered Feb 06 '13 at 22:17

green_knight

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score 5 · Answer 7 · answered Sep 16 '15 at 06:43

We can check by Four ways

The first way is

BOOL flagWayOne = TRUE; 
NSLog(@"The flagWayOne result is - %@",flagWayOne ? @"TRUE":@"FALSE");

The second way is

BOOL flagWayTwo = YES; 
NSLog(@"The flagWayTwo result is - %@",flagWayTwo ? @"YES":@"NO");

The third way is

BOOL flagWayThree = 1;
NSLog(@"The flagWayThree result is - %d",flagWayThree ? 1:0);

The fourth way is

BOOL flagWayFour = FALSE; // You can set YES or NO here.Because TRUE = YES,FALSE = NO and also 1 is equal to YES,TRUE and 0 is equal to FALSE,NO whatever you want set here.
NSLog(@"The flagWayFour result is - %s",flagWayFour ? YES:NO);

score 2 · Answer 8 · answered Jan 17 '14 at 06:01

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NSArray *array1 = [NSArray arrayWithObjects:@"todd1", @"todd2", @"todd3", nil];
bool objectMembership = [array1 containsObject:@"todd1"];
NSLog(@"%d",objectMembership);  // prints 1 or 0

answered Jan 17 '14 at 06:01

Saqib R.

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score 1 · Answer 9 · edited Sep 16 '15 at 06:11

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Here is how you can do it:

BOOL flag = NO;
NSLog(flag ? @"YES" : @"NO");

edited Sep 16 '15 at 06:11

josliber

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answered Sep 16 '15 at 05:42

SAQIB SOHAIL BHATTI

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This is basically a repeat of part of @BoltClock 's answer from four years ago. – jk7 Jan 13 '16 at 17:31

score 1 · Answer 10 · answered Feb 08 '18 at 15:08

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In Swift, you can simply print a boolean value and it will be displayed as true or false.

let flag = true
print(flag) //true

answered Feb 08 '18 at 15:08

Tamás Sengel

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score 0 · Answer 11 · answered Sep 02 '13 at 10:30

0

//assuming b is BOOL. ternary operator helps us in any language.
NSLog(@"result is :%@",((b==YES)?@"YES":@"NO"));

answered Sep 02 '13 at 10:30

Zen Of Kursat

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(b==YES) is the same as just b. as listed, you are relying on the compiler's optimizer to reduce it back down to (b ? @"YES" : @"NO") – Armand Mar 04 '14 at 06:33

score 0 · Answer 12 · answered Nov 25 '21 at 01:53

Direct print bool to integer

BOOL curBool = FALSE;
NSLog(@"curBool=%d", curBool);

-> curBool=0

Convert bool to string

char* boolToStr(bool curBool){
    return curBool ? "True": "False";
}

BOOL curBool = FALSE;
NSLog(@"curBool=%s", boolToStr(curBool));

-> curBool=False

How to print Boolean flag in NSLog?

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