Convert nsdictionary to nsdata

问题:

have an app that can take a picture and then upload to a server. encoding it to base 64 and pass it thru a XMLRPC to my php server.

i want to take the NSDictionary info that is returned from UIImagePickerController delegate

-(void) imagePickerController:(UIImagePickerController *)imagePicker didFinishPickingMediaWithInfo:(NSDictionary *)info

and convert it to NSData so i can encode it.

so, how can i convert NSDictionary to an NSData?

回答1:

You can use an NSKeyedArchiver to serialize your NSDictionary to an NSData object. Note that all the objects in the dictionary will have to be serializable (implement NSCoding at some point in their inheritance tree) in order for this to work.

Too lazy to go through my projects to lift code, so here is some from the Internet:

Encode

NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:yourDictionary forKey:@"Some Key Value"];
[archiver finishEncoding];
[archiver release];
/** data is ready now, and you can use it **/
[data release];

Decode:

NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[self dataFilePath]];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
NSDictionary *myDictionary = [[unarchiver decodeObjectForKey:@"Some Key Value"] retain];
[unarchiver finishDecoding];
[unarchiver release];
[data release];

回答2:

NSDictionary -> NSData:

    NSData *myData = [NSKeyedArchiver archivedDataWithRootObject:myDictionary];

NSData -> NSDictionary:

    NSDictionary *myDictionary = (NSDictionary*) [NSKeyedUnarchiver unarchiveObjectWithData:myData];

回答3:

I know a bit too late, but just in case someone bumps into this same issue. UIImage is not serializable, but you can serialize it using the code:

if your image is JPG:

NSData *imagenBinaria = [NSData dataWithData:UIImageJPEGRepresentation(imagen, 0.0)]; 

// imagen is a UIImage object

if your image is PNG:

NSData *imagenBinaria = [NSData dataWithData:UIImagePNGRepresentation(imagen)]; 

// imagen is a  UIImage object

回答4:

The NSPropertyListSerialization class give you the most control over writing and reading of property lists:

NSDictionary *dictionary = @{@"Hello" : @"World"};
NSData *data = [NSPropertyListSerialization dataWithPropertyList:dictionary
                                            format:NSPropertyListBinaryFormat_v1_0
                                            options:0
                                            error:NULL];

Read:

NSData *data = ...
NSPropertyListFormat *format;
NSDictionary *dictionary = [NSPropertyListSerialization propertyListWithData:data
                                                        options:0
                                                        format:&format
                                                        error:NULL];

回答5:

Three options occur to me on this, two mentioned in other answers NSKeyedArchiver and PropertyList, there is also NSJSONSerialization that gave me the most compact data in a simple test.

NSDictionary *dictionary = @{@"message":@"Message from a cool guy", @"flag":@1};
NSData *prettyJson = [NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:nil];
NSData *compactJson = [NSJSONSerialization dataWithJSONObject:dictionary options:0 error:nil];
NSData *plist = [NSPropertyListSerialization dataWithPropertyList:dictionary
                                                           format:NSPropertyListBinaryFormat_v1_0
                                                          options:0
                                                            error:NULL];
NSData *archived = [NSKeyedArchiver archivedDataWithRootObject:dictionary];`

Size results for the different approaches smallest to largest

• compactJson 46 bytes
• prettyJson 57 bytes
• plist 91 bytes
• archived 316 bytes