How to convert NSValue to NSData and back?

Question

A have a number of NSValue (obtained via KVC valueForKey) that I need to append to an NSData object in order to send it over the netwo

Answer 1

Martin Gordon's answer is getting close, but fortunately you don't have to manually parse the objCType string. There's a function that does that: NSGetSizeAndAlignment. From that you get the size/length of the value obtained from getValue:. This question lead me to the solution.

I ended up creating a category for NSData that allows me to create NSData from NSNumber or NSValue objects:

@interface NSData (GameKitCategory)
+(NSData*) dataWithValue:(NSValue*)value;
+(NSData*) dataWithNumber:(NSNumber*)number;
@end

@implementation NSData (GameKitCategory)
+(NSData*) dataWithValue:(NSValue*)value
{
    NSUInteger size;
    const char* encoding = [value objCType];
    NSGetSizeAndAlignment(encoding, &size, NULL);

    void* ptr = malloc(size);
    [value getValue:ptr];
    NSData* data = [NSData dataWithBytes:ptr length:size];
    free(ptr);

    return data;
}

+(NSData*) dataWithNumber:(NSNumber*)number
{
    return [NSData dataWithValue:(NSValue*)number];
}
@end

I also add a small header before this NSValue/NSNumber data that allows me to decode which property the data is for and how many bytes are in the data section. With that I can restore the value to the remote property.