Is there a way to log all the property values of an Objective-C instance

Question

I was just wondering if there is a quick and easy way of printing out to the log all of the various values of the properties to my class for debugging purposes. Like I would like to know what the values of all of the BOOLs, floats, etc. are.

score 32 · Accepted Answer · edited Jun 20 '20 at 09:12

This question seems the have the answer to your question.

Update:

I got curious and made a catagory:

//Using Xcode 4.5.2 - iOS 6 - LLDB - Automatic Reference Counting

//NSObject+logProperties.h    
@interface NSObject (logProperties)
- (void) logProperties;
@end

//NSObject+logProperties.m
#import "NSObject+logProperties.h"
#import <objc/runtime.h>

@implementation NSObject (logProperties)

- (void) logProperties {

    NSLog(@"----------------------------------------------- Properties for object %@", self);

    @autoreleasepool {
        unsigned int numberOfProperties = 0;
        objc_property_t *propertyArray = class_copyPropertyList([self class], &numberOfProperties);
        for (NSUInteger i = 0; i < numberOfProperties; i++) {
            objc_property_t property = propertyArray[i];
            NSString *name = [[NSString alloc] initWithUTF8String:property_getName(property)];
            NSLog(@"Property %@ Value: %@", name, [self valueForKey:name]);
        }
        free(propertyArray);
    }    
    NSLog(@"-----------------------------------------------");
}

@end

Include it in your class: #import "NSObject+logProperties.h"

and call [self logProperties]; to those properties!

@Tieme I like _this kind of thing_.. but I like it to look pretty, and be SUPER short, hence.. [A concise category on NSObject to log all declared properties, pretty-like, using minimal SLOC.](https://gist.github.com/b51a60dac974b9f952a0) (Also, yours made my programs crash ) — Alex Gray, May 13 '14 at 16:02

score 9 · Answer 2 · answered Feb 21 '19 at 16:50

9

There are now these methods on NSObject :

@interface NSObject (Private)
-(id)_ivarDescription;
-(id)_shortMethodDescription;
-(id)_methodDescription;
@end

In swift:

myObject.perform("_ivarDescription")

Thanks to this article

answered Feb 21 '19 at 16:50

GaétanZ

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score 8 · Answer 3 · answered Dec 17 '12 at 22:01

The current answers just show how to do it for properties. If you want every instance variable printed out you could do something like the below.

- (void)logAllProperties {
    unsigned int count;
    Ivar *ivars = class_copyIvarList([self class], &count);
    for (unsigned int i = 0; i < count; i++) {
        Ivar ivar = ivars[i];

        const char *name = ivar_getName(ivar);
        const char *type = ivar_getTypeEncoding(ivar);
        ptrdiff_t offset = ivar_getOffset(ivar);

        if (strncmp(type, "i", 1) == 0) {
            int intValue = *(int*)((uintptr_t)self + offset);
            NSLog(@"%s = %i", name, intValue);
        } else if (strncmp(type, "f", 1) == 0) {
            float floatValue = *(float*)((uintptr_t)self + offset);
            NSLog(@"%s = %f", name, floatValue);
        } else if (strncmp(type, "@", 1) == 0) {
            id value = object_getIvar(self, ivar);
            NSLog(@"%s = %@", name, value);
        }
        // And the rest for other type encodings
    }
    free(ivars);
}

Although I wouldn't particularly suggest doing this in practice, but if it's for debug purposes then that's fine. You could implement this as a category on NSObject and keep it lying around for use when debugging. If completed for all type encodings then it could make for a very nice little method.

score 0 · Answer 4 · answered Dec 17 '12 at 21:42

0

yes, one way would be to ask for all properties and then use KVC for example:

//properties
unsigned int cProperties = 0;
objc_property_t *props = class_copyPropertyList(self.class, &cProperties);
for(int i = 0; i < cProperties; i++) {
    const char *name = property_getName(props[i]);
    NSLog(@"%@=%@", name, [self valueForKey:name];
}

an alternate way is to go through all the methods of a class, get the return type, invoke and print it

answered Dec 17 '12 at 21:42

Daij-Djan

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Of course this only works for objects, not primitive types like floats and bool. How would you go about to solve the problem with the format specifier in your NSLog that currently logs objects for properties and crashes on primitive types (%@)? – Mario Dec 17 '12 at 21:56
see the answer above by matt – Daij-Djan Dec 17 '12 at 22:31

score -2 · Answer 5 · answered Dec 17 '12 at 21:46

-2

The quick and dirty would be to override debugDescription:

-(NSString*)debugDescription {
    NSString *str = [[NSString alloc] initWithFormat:@"My BOOL 1: %d, My Float: %f", self.myBool, self.myFoat];
    return str;
}

Of course, if your object is complex, this could be time consuming.

answered Dec 17 '12 at 21:46

Mike D

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only if you like typing ;) or if it is only for one object! – Daij-Djan Dec 17 '12 at 21:54
1

@Daij-Djan Hence the disclaimer. – Mike D Dec 17 '12 at 21:58

Is there a way to log all the property values of an Objective-C instance

5 Answers5

Update:

Linked