Understanding NSLog syntax

Question

(I'm a cocoa beginner and ) I'm wondering why we should do:

NSLog(@"this is the variable value: %d",variable);

and not something like this:

[NSLog outputThis:@"this is the variable value: %d" param:variable];

Because second statement calls `outputThis:param:` method on `NSLog` object. `NSLog` is just a function in Cocoa framework. — Eimantas, Jun 25 '12 at 13:47
yes but it could have been a class method for a class NSLog, like [NSString stringWithString:@"this is a string"]; ? — tahir, Jun 25 '12 at 13:50
NSLog does not "sound" like class. NSLogger would've been better choice for a class name. Now it's just an action. — Eimantas, Jun 25 '12 at 13:57
because the second one looks shit and we should feel blessed for anything that looks more like C ;) — Dominic, Dec 04 '13 at 22:29

score 19 · Accepted Answer · answered Jun 25 '12 at 13:51

19

I agree this is pretty confusing when you're starting out. The main reason is that the NSLog method, like many others in Core Foundation, is a C-based API, rather than an Objective-C API. C-style functions look like this myFunction(myParameter1, myParameter2).

All the GUI stuff you're probably used to [UIView presentModalViewController:] etc is based around an Objective-C API, with the square brackets that you've seen for functions (called selectors in Obj-C) . The Objective-C language sits on top of C, so you will find both styles in most apps.

answered Jun 25 '12 at 13:51

Ben Clayton

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Apple decides everything, and we 'll like it – onmyway133 Jul 22 '14 at 04:27
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^ is the story of every iOS developer XD – Pranav Kasetti Mar 08 '21 at 18:44

Alladinian · Answer 2 · 2017-09-20T08:09:15.437

7

NSLog may seem like a class, but it isn't.

NSLog is a FoundationKit function for printing debug statements to the console. It is defined in NSObjCRuntime.h:

void NSLog(NSString format, ...);

There is a good amount of information here: ~~http://cocoadev.com/wiki/NSLog~~

EDIT: As @fyngyrz pointed out, the page is dead. So here is a wayback-machine version of the page from 2012

edited Sep 20 '17 at 08:09

answered Jun 25 '12 at 13:53

Alladinian

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No, there isn't. The page is gone. – fyngyrz Sep 20 '17 at 00:59
@fyngyrz Thanx. Edited the answer. – Alladinian Sep 20 '17 at 08:09

score 6 · Answer 3 · edited Jun 25 '12 at 14:02

6

As I understand it, NSLog isn't an Objective C function but a C function built into the foundation of Cocoa. Therefore it conforms to basic C functions with variadic arguments.

edited Jun 25 '12 at 14:02

John Topley

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answered Jun 25 '12 at 13:50

Ryan Poolos

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Understanding NSLog syntax

3 Answers3