How can we store into an NSDictionary What is the difference between NSDictionary and NSMutableDictionary

Question

I am developing an application in which I want to use an NSDictionary  Can anyone please send me a sample code explaining the procedure how to use an NSDictionary to store Data with a perfect example

User · Answer

NSDictionary    dict    NSDictionary dictionaryWithObject    String  forKey    Test    NSMutableDictionary  anotherDict    NSMutableDictionary dictionary     anotherDict setObject  dict forKey   sub-dictionary-key     anotherDict setObject    Another String  forKey    another test     NSLog   Dictionary      Mutable Dictionary       dict  anotherDict       now we can save these to a file NSString    savePath        Documents Saved data  stringByExpandingTildeInPath    anotherDict writeToFile  savePath atomically  YES      and restore them NSMutableDictionary   restored    NSDictionary dictionaryWithContentsOfFile  savePath

User · Answer

The NSDictionary and NSMutableDictionary docs are probably your best bet  They even have some great examples on how to do various things  like        create an NSDictionary  NSArray  keys    NSArray arrayWithObjects   key1     key2   nil   NSArray  objects    NSArray arrayWithObjects   value1     value2   nil   NSDictionary  dictionary    NSDictionary dictionaryWithObjects objects                                                         forKeys keys       iterate over it  for  id key in dictionary        NSLog   key      value       key   dictionary objectForKey key          make it mutable  NSMutableDictionary  mutableDict    dictionary mutableCopy    Note  historic version before 2010    dictionary mutableCopy  autorelease      and alter it   mutableDict setObject   value3  forKey   key3        then store it to a file   mutableDict writeToFile   path to file  atomically YES       and read it back again  NSMutableDictionary  anotherDict    NSMutableDictionary dictionaryWithContentsOfFile   path to file        read a value  NSString  x    anotherDict objectForKey   key1         check if a key exists  if    anotherDict objectForKey   key999      nil   NSLog   that key is not there         use scary futuristic syntax  From 2014 you can actually just type dict   key   rather than  dict objectForKey   key

User · Answer

The key difference  NSMutableDictionary can be modified in place  NSDictionary cannot  This is true for all the other NSMutable  classes in Cocoa  NSMutableDictionary is a subclass of NSDictionary  so everything you can do with NSDictionary you can do with both  However  NSMutableDictionary also adds complementary methods to modify things in place  such as the method setObject forKey    You can convert between the two like this   NSMutableDictionary  mutable     dict mutableCopy  autorelease   NSDictionary  dict     mutable copy  autorelease      Presumably you want to store data by writing it to a file  NSDictionary has a method to do this  which also works with NSMutableDictionary    BOOL success    dict writeToFile    file path  atomically YES     To read a dictionary from a file  there s a corresponding method   NSDictionary  dict    NSDictionary dictionaryWithContentsOfFile    file path      If you want to read the file as an NSMutableDictionary  simply use   NSMutableDictionary  dict    NSMutableDictionary dictionaryWithContentsOfFile    file path

[iphone] How can we store into an NSDictionary? What is the difference between NSDictionary and NSMutableDictionary?

Examples related to iphone

Examples related to objective-c

Examples related to nsdictionary

Examples related to nsmutabledictionary