Accessing C arrays(int[], float[], etc..) using Objective-C runtime - iphone

Question

I'm trying to save all the variables in my class into NSUserDefaults using objc/runtime. And below is the code I'm using.
NSUInteger count;
Ivar *iVars = class_copyIvarList([self class], &count);
for (NSUInteger i=0; i<count; i++)
{
Ivar var = iVars[i];
NSString *varName = [NSString stringWithCString:ivar_getName(var) encoding:NSUTF8StringEncoding];
NSString *varType = [NSString stringWithCString:ivar_getTypeEncoding(var) encoding:NSUTF8StringEncoding];
if([varType hasPrefix:#"["])
{
NSLog(#"Array");
id var1 = [_manager valueForKey:varName];
NSLog(#"--- %#", var1);
NSData *data = [NSData dataWithBytes:&([_manager valueForKey:varName]) length:sizeof([_manager valueForKey:varName])]
[[NSUserDefaults standardUserDefaults] setObject:[_manager valueForKey:varName] forKey:varName];
}
else
{
NSLog(#"NonArray");
NSLog(#"--- %#", [_manager valueForKey:varName]);
[[NSUserDefaults standardUserDefaults] setObject:[_manager valueForKey:varName] forKey:varName];
}
}
free(iVars);
The problem is that, when there are only primitive datatypes, the above code works just fine. But, when I try to access a array variable like int[], or float[], it gets crashed with SIGABRT. it is not showing any other messages.
valueForKey doesn't return any values for C arrays.
If anybody know how to load values for C-arrays in runtime, please help.
Thanks in advance,
Suran

Answer 1

Unless you always provide a paired length method, your program will never know the length of the array returned. So... you will need to do some work someplace to accomplish this without a crash.
If I really wanted to do what you're doing, I would make the class itself create the array, providing NSData. If this is common, you may want to use a convention:
- (int*)pixelBuffer;
- (NSData *)pixelBufferForSerialization; // << returns a deep copy of
// self.pixelBuffer as an
// NSData instance.
So your above implementation would see that the property defines a scalar array, and then request NSData * data = obj.pixelBufferForSerialization; instead of trying to produce the data itself.
Update
It's best to let the class do it. Here's how to create NSData using such an array:
#interface DataManager : NSObject
{
#private
int* things;
size_t nThings;
}
- (int*)things;
- (NSData *)thingsAsNSData;
#end
#implementation DataManager
- (int*)things
{
return things;
}
- (NSData *)thingsAsNSData
{
// note: you may need to choose an endianness for serialization
if (0 == nThings) return [NSData data];w
return [NSData dataWithBytes:things length:nThings * sizeof(things[0])];
}
#end
Again - you want the class to create the data because it knows its own structure best.