Using NSLog for debugging

I have the following code snippet in my Xcode:

NSString *digit [[sender titlelabel] text];
NSLog([digit]);

I tried to build the application and am getting the following warning message for the line NSLog([digit]);

Warning: Format not a string literal and no format arguments

Can you advise me how I can resolve this warning message? What does the message actually mean?

Try this piece of code:

NSString *digit = [[sender titlelabel] text];
NSLog(@"%@", digit);

The message means that you have incorrect syntax for using the digit variable. If you're not sending it any message - you don't need any brackets.

Use NSLog() like this:

NSLog(@"The code runs through here!");

Or like this - with placeholders:

float aFloat = 5.34245;
NSLog(@"This is my float: %f \n\nAnd here again: %.2f", aFloat, aFloat);

In NSLog() you can use it like + (id)stringWithFormat:(NSString *)format, ...

float aFloat = 5.34245;
NSString *aString = [NSString stringWithFormat:@"This is my float: %f \n\nAnd here again: %.2f", aFloat, aFloat];

You can add other placeholders, too:

float aFloat = 5.34245;
int aInteger = 3;
NSString *aString = @"A string";
NSLog(@"This is my float: %f \n\nAnd here is my integer: %i \n\nAnd finally my string: %@", aFloat, aInteger, aString);

Why do you have the brackets around digit? It should be

NSLog("%@", digit);

You're also missing an = in the first line...

NSString *digit = [[sender titlelabel] text];

The proper way of using NSLog, as the warning tries to explain, is the use of a formatter, instead of passing in a literal:

Instead of:

NSString *digit = [[sender titlelabel] text];
NSLog(digit);

Use:

NSString *digit = [[sender titlelabel] text];
NSLog(@"%@",digit);

It will still work doing that first way, but doing it this way will get rid of the warning.

type : BOOL DATA (YES/NO) OR(1/0)

BOOL dtBool = 0; 

OR

BOOL dtBool = NO;
NSLog(dtBool ? @"Yes" : @"No");

OUTPUT : NO

type : Long

long aLong = 2015;
NSLog(@"Display Long: %ld”, aLong);

OUTPUT : Display Long: 2015

long long veryLong = 20152015;
NSLog(@"Display very Long: %lld", veryLong);

OUTPUT : Display very Long: 20152015

type : String

NSString *aString = @"A string";
NSLog(@"Display string: %@", aString);

OUTPUT : Display String: a String

type : Float

float aFloat = 5.34245;
NSLog(@"Display Float: %F", aFloat);

OUTPUT : isplay Float: 5.342450

type : Integer

int aInteger = 3;    
NSLog(@"Display Integer: %i", aInteger);

OUTPUT : Display Integer: 3

NSLog(@"\nDisplay String: %@ \n\n Display Float: %f \n\n Display Integer: %i", aString, aFloat, aInteger);

OUTPUT : String: a String

Display Float: 5.342450

Display Integer: 3

http://luterr.blogspot.sg/2015/04/example-code-nslog-console-commands-to.html

NSLog(@"%@", digit);

what is shown in console?

NSLog([digit]); // [] are the messages in Objective-C, just like methods or functions in other programming languages

Since you just need to print the value of 'digit'

Either you can call -

NSLog(digit); // A warning would occur - Format string is not a string literal (potentially insecure)

OR

NSLog(@"%@",digit]); // But if you use %@ to reference the object, the warning will go away.

Both the methods will work but the second one is the right way of logging to console.