Loop through all object properties at runtime - iphone

Question

I want to create an Objective-C base class that performs an operation on all properties (of varying types) at runtime. Since the names and types of the properties will not always be known, how can I do something like this?
#implementation SomeBaseClass
- (NSString *)checkAllProperties
{
for (property in properties) {
// Perform a check on the property
}
}
EDIT: This would be particularly useful in a custom - (NSString *)description: override.

Answer 1

To expand on mvds' answer (started writing this before I saw his), here's a little sample program that uses the Objective-C runtime API to loop through and print information about each property in a class:
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#interface TestClass : NSObject
#property (nonatomic, retain) NSString *firstName;
#property (nonatomic, retain) NSString *lastName;
#property (nonatomic) NSInteger *age;
#end
#implementation TestClass
#synthesize firstName;
#synthesize lastName;
#synthesize age;
#end
int main(int argc, char *argv[]) {
#autoreleasepool {
unsigned int numberOfProperties = 0;
objc_property_t *propertyArray = class_copyPropertyList([TestClass class], &numberOfProperties);
for (NSUInteger i = 0; i < numberOfProperties; i++)
{
objc_property_t property = propertyArray[i];
NSString *name = [[NSString alloc] initWithUTF8String:property_getName(property)];
NSString *attributesString = [[NSString alloc] initWithUTF8String:property_getAttributes(property)];
NSLog(#"Property %# attributes: %#", name, attributesString);
}
free(propertyArray);
}
}
Output:
Property age attributes: T^q,Vage
Property lastName attributes: T#"NSString",&,N,VlastName
Property firstName attributes: T#"NSString",&,N,VfirstName
Note that this program needs to be compiled with ARC turned on.

Answer 2

Use
objc_property_t * class_copyPropertyList(Class cls, unsigned int *outCount)
and read https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html on how to do this exactly.
Some code to get you going:
#import <objc/runtime.h>
unsigned int count=0;
objc_property_t *props = class_copyPropertyList([self class],&count);
for ( int i=0;i<count;i++ )
{
const char *name = property_getName(props[i]);
NSLog(#"property %d: %s",i,name);
}

Answer 3

Adding some detial to #mvds:
unsigned int count=0;
objc_property_t *props = class_copyPropertyList([self class],&count);
for ( int i=0;i<count;i++ )
{
const char *name = property_getName(props[i]);
NSString* dataToGet = [NSString swf:#"%s",name];
#try { // in case of this pair not key value coding-compliant
id value = [barButton valueForKey:dataToGet];
NSLog(#"prop %d: %s %#",i,name, value);
} #catch (NSException *exception) {
// NSLog(#"Exception:%#",exception);
}
#finally {
// Display Alternative
}
}
Please give #mvds the upvote.