Using NSLog for debugging

Question

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?

Solution 1

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.

Solution 2

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);

Solution 3

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];

Solution 4

NSLog(@"%@", digit);

what is shown in console?

Solution 5

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.

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