How to add to an NSDictionary

Question

I was using a NSMutableArray and realized that using a dictionary is a lot simpler for what I am trying to achieve   I want to save a key as a NSString and a value as an int in the dictionary  How is this done   Secondly  what is the difference between mutable and a normal dictionary

User · Answer

You want to ask is  what is the difference between a mutable and a non-mutable array or dictionary    Many times there different terms are used to describe things that you already know about   In this case  you can replace the term  mutable  with  dynamic   So  a mutuable dictionary or array is one that is  dynamic  and can change at runtime  whereas a non-mutable dictionary or array is one that is  static  and defined in your code and does not change at runtime  in other words  you will not be adding  deleting or possibly sorting the elements    As to how it is done  you are asking us to repeat the documentation here   All you need to do is to search in sample code and the Xcode documentation to see exactly how it is done   But the mutable thing threw me too when I was first learning  so I ll give you that one

User · Answer

A mutable dictionary can be changed  i e  you can add and remove objects  An immutable is fixed once it is created   create and add   NSMutableDictionary  dict     NSMutableDictionary alloc initWithCapacity 10    dict setObject  NSNumber numberWithInt 42  forKey   A cool number      and retrieve    int myNumber     dict objectForKey   A cool number   intValue

User · Answer

Update version Objective-C Create  NSDictionary  dictionary       quot myKey1 quot    7    quot myKey2 quot    5     Change  NSMutableDictionary  mutableDictionary    dictionary mutableCopy         Make the dictionary mutable to change add mutableDictionary   quot myKey3 quot      3   The short-hand syntax is called Objective-C Literals  Swift Create  var dictionary     quot myKey1 quot   7   quot myKey2 quot   5   Change  dictionary  quot myKey3 quot     3

User · Answer

For reference  you can also utilize initWithDictionary to init the NSMutableDictionary with a literal one   NSMutableDictionary buttons     NSMutableDictionary alloc  initWithDictionary           touch    0        app    0        back    0        volup    0        voldown    0

User · Answer

By setting you d use setValue  id value forKey  id key method of NSMutableDictionary object   NSMutableDictionary  dict     NSMutableDictionary alloc  init    dict setValue  NSNumber numberWithInt 5  forKey   age      Or in modern Objective-C   NSMutableDictionary  dict     NSMutableDictionary alloc  init   dict   age      5    The difference between mutable and  normal  is  well  mutability  I e  you can alter the contents of NSMutableDictionary  and NSMutableArray  while you can t do that with  normal  NSDictionary and NSArray

User · Answer

When ever the array is declared  then only we have to add the key-value s in NSDictionary like  NSDictionary  normalDict     NSDictionary alloc initWithObjectsAndKeys   Value1    Key1    Value2    Key2    Value3    Key3  nil     we cannot add or remove the key values in this NSDictionary  Where as in NSMutableDictionary we can add the objects after intialization of array also by using this method   NSMutableDictionary  mutableDict     NSMutableDictionary alloc init     mutableDict setObject   Value1  forKey   Key1     mutableDict setObject   Value2  forKey   Key2     mutableDict setObject   Value3  forKey   Key3      for removing the key value we have to use the following code   mutableDict removeObject   Value1  forKey   Key1

[iphone] How to add to an NSDictionary

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