Is It Possible to NSLog C Structs (Like CGRect or CGPoint)?

Question

I want to be able to debug C structures without having to explicitly type every property that they consist of.

i.e. I want to be able to do something like this:

CGPoint cgPoint = CGPointMake(0,0);
NSLog(@"%@",cgPoint);

Obviously the '%@' won't work, hence the question.

Try LOG_EXPR from the VTPG_Common library: http://vgable.com/blog/tag/log_expr/ — CodeSmile, Sep 16 '13 at 13:42

score 806 · Accepted Answer · edited Jun 13 '11 at 19:31

806

You can try this:

NSLog(@"%@", NSStringFromCGPoint(cgPoint));

There are a number of functions provided by UIKit that convert the various CG structs into NSStrings. The reason it doesn't work is because %@ signifies an object. A CGPoint is a C struct (and so are CGRects and CGSizes).

edited Jun 13 '11 at 19:31

jscs

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answered Feb 15 '09 at 03:18

Alex

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With AppKit on OS X you would need to convert to an `NSPoint` and then call `NSStringFromPoint`. For example: `NSStringFromPoint(NSPointFromCGPoint(point))` – Alex Aug 22 '12 at 17:56
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NSLog(@"%@", CGRectCreateDictionaryRepresentation(rect)); – Abhishek Bedi Nov 20 '12 at 10:16
Similar to UI, MK, CL prefixes which while all have meanings to it and need to import a respective .h file like :UIKit, MapKit, CoreLocation; Does the CG prefix mean I should import anything? If not is is just a naming convention?! – mfaani Mar 16 '16 at 20:42

score 236 · Answer 2 · edited Jun 13 '11 at 19:04

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There are a few functions like:

NSStringFromCGPoint  
NSStringFromCGSize  
NSStringFromCGRect  
NSStringFromCGAffineTransform  
NSStringFromUIEdgeInsets

An example:

NSLog(@"rect1: %@", NSStringFromCGRect(rect1));

edited Jun 13 '11 at 19:04

marzapower

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answered Mar 04 '11 at 15:20

steve

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These are the: "single thing in all of iOS development that is most useful but least known" !! Heh – Fattie Feb 21 '14 at 15:12
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Note: for Cocoa (OS X) development, these functions don't have "CG" in the name. – peterflynn Jul 22 '15 at 22:41

score 18 · Answer 3 · answered Nov 20 '12 at 10:17

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NSLog(@"%@", CGRectCreateDictionaryRepresentation(rect));

answered Nov 20 '12 at 10:17

Abhishek Bedi

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score 13 · Answer 4 · answered Feb 15 '09 at 03:50

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I use the following macro to help me out with NSRect:

#define LogRect(RECT) NSLog(@"%s: (%0.0f, %0.0f) %0.0f x %0.0f",
    #RECT, RECT.origin.x, RECT.origin.y, RECT.size.width, RECT.size.height)

You could do something similar for CGPoint:

@define LogCGPoint(POINT) NSLog(@"%s: (%0.0f, %0.0f)",
    #POINT POINT.x, POINT.y);

Using it as follows:

LogCGPoint(cgPoint);

Would produce the following:

cgPoint: (100, 200)

answered Feb 15 '09 at 03:50

e.James

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Why not just use the built in [UIKit String Conversion Functions](http://developer.apple.com/library/ios/documentation/UIKit/Reference/UIKitFunctionReference/Reference/reference.html#//apple_ref/doc/uid/TP40006894-CH3-SW34)? – ma11hew28 Oct 20 '11 at 17:58
I do now. Those are exatly the functions that Alex and steve posted in their answers. – e.James Oct 20 '11 at 19:34
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Would it be worth editing the answer and **adding a note** at the top "For historic interest only...". I always do that, for example http://stackoverflow.com/questions/402/iphone-app-in-landscape-mode/2530953#2530953 http://stackoverflow.com/questions/5492479/do-i-get-more-accurate-or-faster-accelerometer-readings-with-core-motion/5492892#5492892 http://stackoverflow.com/questions/4212628/whats-the-difference-between-setting-an-object-to-nil-vs-sending-it-a-release/4212826#4212826 (*"It's worth noting that this post from the previous decade, is really now only of historic interest."*) etc – Fattie Feb 21 '14 at 15:18
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This answer is still useful, despite the existence of UIKit conversion functions, because there other structs in other frameworks, which do not have NSStringFrom helpers (eg. MKCoordinateRegion). – Greg Bell Nov 19 '14 at 22:41

score 10 · Answer 5 · answered Jul 08 '13 at 12:33

You can use NSValue for this. An NSValue object is a simple container for a single C or Objective-C data item. It can hold any of the scalar types such as int, float, and char, as well as pointers, structures, and object ids.

Example:

  CGPoint cgPoint = CGPointMake(10,30);
    NSLog(@"%@",[NSValue valueWithCGPoint:cgPoint]);

OUTPUT : NSPoint: {10, 30}

Hope it helps you.

score 6 · Answer 6 · edited Jan 09 '18 at 18:40

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Yes, you can use bellow few functions like: First you have to convert CGPoint struct into string, see example

1) NSStringFromCGPoint,  
2) NSStringFromCGSize,  
3) NSStringFromCGRect,  
4) NSStringFromCGAffineTransform,  
5) NSStringFromUIEdgeInsets,

For example:

1) NSLog(@"NSStringFromCGPoint = %@", NSStringFromCGRect(cgPointValue));

Like this...

edited Jan 09 '18 at 18:40

Hussain Shabbir

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answered Mar 10 '17 at 14:26

Vaibhav Shiledar

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score 5 · Answer 7 · edited Jun 20 '13 at 06:05

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Since Stack Overflow’s broken RSS just resurrected this question for me, here’s my almost-general solution: JAValueToString

This lets you write JA_DUMP(cgPoint) and get cgPoint = {0, 0} logged.

edited Jun 20 '13 at 06:05

NANNAV

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answered Jun 13 '11 at 19:29

Jens Ayton

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I did that and I got compile error. Sometimes address of property expression required or something – user4951 Jun 19 '11 at 10:58
@Jim Thio: the macro is set up in such a way that the object being inspected must be an lvalue. (I can’t remember why; something about not being able to handle C strings properly otherwise.) In short, assign your property to a temporary variable, then call JA_DUMP on that. – Jens Ayton Jun 19 '11 at 22:11

score 2 · Answer 8 · answered Mar 30 '16 at 09:02

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NSLog(@"%@",CGRectCreateDictionaryRepresentation(rect));

answered Mar 30 '16 at 09:02

UdayM

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score 0 · Answer 9 · answered Nov 08 '22 at 14:14

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Use Objective-C way to create objects from C primitives

CGRect rect = CGRectMake(1, 2, 3, 4);
CGSize size = CGSizeMake(1, 2);
NSLog(@"%@, %@",@(rect), @(size));

Output: NSRect: {{1, 2}, {3, 4}}, NSSize: {1, 2}

answered Nov 08 '22 at 14:14

Consul

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Is It Possible to NSLog C Structs (Like CGRect or CGPoint)?

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