Objective-C Log Handling

NSLog method

In order to print logs, we use the NSLog method in Objective-C programming language which we have used right from the Hello World example.

Let us look at a simple code that would print the words "Hello World" −

#import <Foundation/Foundation.h>
int main() {
   NSLog(@"Hello, World! \n");
   return 0;
}

Now, when we compile and run the program, we will get the following result.

2013-09-16 00:32:50.888 demo[16669] Hello, World! 

Disabling logs in Live apps

Since the NSLogs we use in our application, it will be printed in logs of device and it is not good to print logs in a live build. Hence, we use a type definition for printing logs and we can use them as shown below.

#import <Foundation/Foundation.h>
#if DEBUG == 0
#define DebugLog(...)
#elif DEBUG == 1
#define DebugLog(...) NSLog(__VA_ARGS__)
#endif
int main() {
   DebugLog(@"Debug log, our custom addition gets \
   printed during debug only" );
   NSLog(@"NSLog gets printed always" );     
   return 0;
}

Now, when we compile and run the program in debug mode, we will get the following result.

2013-09-11 02:47:07.723 demo[618] Debug log, our custom addition gets printed during debug only
2013-09-11 02:47:07.723 demo[618] NSLog gets printed always

Now, when we compile and run the program in release mode, we will get the following result.

2013-09-11 02:47:45.248 demo[3158] NSLog gets printed always