Graphics Programs Reference
In-Depth Information
how memory is allocated. In practice, you pass
kCFAllocatorDefault
and let the
system make that choice.
Once created, a
CFUUIDRef
is just an array of bytes and, if represented as a string, will
look something like this:
28153B74-4D6A-12F6-9D61-155EA4C32167
This UUID will be used in two ways: it will be the key in the
BNRImageStore
's dic-
tionary and in a later chapter, it will be the name of the image file on the filesystem. Be-
cause keys in a dictionary and paths on the filesystem are typically strings, we want to
represent the UUID as a string instead of an array of bytes.
You can create a string object from a
CFUUIDRef
by calling the C function
CFUUIDCreateString
. In
DetailViewController.m
, add the following line of
code in
imagePickerController:didFinishPickingMediaWithInfo:
.
- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
CFUUIDRef newUniqueID = CFUUIDCreate (kCFAllocatorDefault);
// Create a string from unique identifier
CFStringRef newUniqueIDString =
CFUUIDCreateString (kCFAllocatorDefault, newUniqueID);
Notice that
newUniqueIDString
's type is
CFStringRef
. The
imageKey
property
of
BNRItem
is an
NSString
. Clearly, you need some way to move between
CFStringRef
and
NSString
to set the
imageKey
property.
Fortunately, many classes in Core Foundation are
toll-free bridged
with their Objective-C
counterpart. For example,
CFStringRef
is toll-free bridged with
NSString
;
CFAr-
rayRef
with
NSArray
. Instances of classes that are toll-free bridged look exactly the
same as their counterpart in memory. Therefore, you can use a simple C-style typecast to
treat a toll-free bridged Core Foundation object as an Objective-C object.
Typecast
newUniqueIDString
and set it as the
imageKey
of the selected
BNRItem
in
imagePickerController:didFinishPickingMediaWithInfo:
. Also,
place this image in the
BNRImageStore
.
- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
CFUUIDRef newUniqueID = CFUUIDCreate (kCFAllocatorDefault);
