A message send is always surrounded by square brackets, and it always has at least two parts:
a pointer to the object that is receiving the message
the name of the method to be triggered
A message send (like a function call) can also have arguments. Let’s look at an example.
NSDate objects represent a particular date and time. An instance of NSDate can tell you the difference (in seconds) between the date/time it represents and 12:00AM (GMT) on Jan 1, 1970. Ask yours this question by sending the message timeIntervalSince1970 to the NSDate object pointed to by now.
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[])
{
@autoreleasepool {
NSDate *now = [NSDate date];
NSLog(@"The date is %@", now);
double seconds = [now timeIntervalSince1970];
NSLog(@"It has been %f seconds since the start of 1970.", seconds);
}
return 0;
}
Now say you want a new date object – one that is 100,000 seconds later from the one you already have.
The NSDate class has a method called dateByAddingTimeInterval:. You can send this message to the original date object to get the new date object. This method takes an argument: the number of seconds to add. Use it to create a new date object in your main() function:
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[])
{
@autoreleasepool {
NSDate *now = [NSDate date];
NSLog(@"The date is %@", now);
double seconds = [now timeIntervalSince1970];
NSLog(@"It has been %f seconds since the start of 1970.", seconds);
NSDate *later = [now dateByAddingTimeInterval:100000];
NSLog(@"In 100,000 seconds it will be %@", later);
}
return 0;
}
In the message send [now dateByAddingTimeInterval:100000],
