NSDictionary category

Each method in the NSDictionary category corresponds to a method in the NSDictionary class, but provides a secure version of the functionality. For more information about the functionality and usage, see NSDictionary in developer.apple.com.

Note the following:

•The url parameter in the category methods must be a file URL, and point to a regular file.

•The category methods return an NSError object. The methods set the properties on the object as described in NSError objects that secure Objective-C methods return.

The following table shows each added method and its corresponding method in NSDictionary.

Table 28.   NSDictionary category methods

Method in category

Corresponding method in NSDictionary

 
   dictionaryWithContentsOfSecureFile:
+ (id)   (NSString *)path
   error:(
      NSError *__autoreleasing *)error;
 
+ (id)dictionaryWithContentsOfFile:
   (NSString *)path;
 
+ (id)
   dictionaryWithContentsOfSecureURL:
   (NSURL *)aURL
   error:(
      NSError *__autoreleasing *)error;
 
+ (id)dictionaryWithContentsOfURL:
   (NSURL *)aURL;
 
 
- (id)initWithContentsOfSecureFile:
   (NSString *)path
   error:(
      NSError *__autoreleasing *)error;
 
- (id)initWithContentsOfFile:
   (NSString *)path;
 
 
- (id)initWithContentsOfSecureURL:
   (NSURL *)aURL
   error:(
      NSError *__autoreleasing *)error;
 
- (id)initWithContentsOfURL:
   (NSURL *)aURL;
 
 
- (BOOL)writeToSecureFile:
   (NSString *)path 
   atomically:(BOOL)flag
   error:(
      NSError *__autoreleasing *)error;
 
- (BOOL)writeToFile:
   (NSString *)path 
   atomically:(BOOL)flag;
 
 
- (BOOL)writeToSecureURL:
   (NSURL *)aURL 
   atomically:(BOOL)flag
   error:(
      NSError *__autoreleasing *)error;
 
- (BOOL)writeToURL:
   (NSURL *)aURL 
   atomically:(BOOL)flag;
 

Example:

The following example shows how to use NSDictionary and NSMutableDictionary category methods to:

1. Create a secure file and write data to it from a NSMutableDictionary object.
2. Read the contents of the secure file into an NSDictionary object.

For brevity, the example does not include error handling.

- (void)NSDictionaryCategoryExample
{
	NSError *error;
 
	// Create and populate a dictionary.
	NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"baseball",
					 @"white", @"basketball", @"orange", nil];
 
	// Write the dictionary to a secure file.
	NSString *secureFileName = @"/tmp/secureDictionary";
	[dict writeToSecureFile:secureFileName atomically:TRUE error:&error];
 
	// Create a dictionary with the contents of the secure file.
	NSDictionary *dictCopy = [[NSDictionary alloc] 
					 initWithContentsOfSecureFile:secureFileName error:&error];
 
	// Note: The contents of objects 'dict' and 'dictCopy' are identical.
}