How to insert a new key with value in dictionary

Question

I want to insert a key with a corresponding value in an existing dictionary...

I am able to set values for existing keys in the dictionary, but I am not able to add a new key value...

Any help would be appreciated.

Lyly

Answer 1

Use NSMutableDictionary

NSMutableDictionary *yourMutableDictionary = [NSMutableDictionary alloc] init];
[yourMutableDictionary setObject:@"Value" forKey:@"your key"];

Update for Swift:

The following is the exact swift replica for the code mentioned above

var yourMutableDictionary = NSMutableDictionary()
yourMutableDictionary.setObject("Value", forKey: "Key")

But i would suggest you to go with Swift Dictionary way.

var yourMutableDictionary = [String: AnyObject]() //Open close bracket represents initialization

//The reason for AnyObject is a dictionary's value can be String or
//Array or Dictionary so it is generically written as AnyObject

yourMutableDictionary["Key"] = "Value"

Lornalorne

how to know whether the given key is existed or not in dictionary – Lyly

[yourMutableDictionary allKeys]; This will return an array of all keys in that dictionary and compare that with your given key and know it – Lornalorne

By the way, if you have to convert back to a NSDictionary you can by casting it like yourNSDictionary = yourMutableDictionary as NSDictionary. – Accessary

and how to add any object class as value and int as key? – Sealskin

Answer 2

NSDictionnary is immutable. Use NSMuteableDictiory instead.

adding Objects: setObject:forKey:

Testing if key is present:

[[aDict allKeys] containsObject:@"key"];

Rouge

for nsmutable dictionary how to insert new key value – Lyly

Answer 3

NSMutableDictionary *dict = [[NSMutableDictionary alloc]init];

By using this method we can add the new value to NSMutableDictionary

[dict setObject:@"Value" forKey:@"Key"];

To know wheather the key exist in dictionary

[[dict allKeys] containsObject:@"key"];

Devitt

cv::Mat as value and int as key how to add it to NSMutableDictionary? – Sealskin

Answer 4

Hi I am getting the content from json in the format of dictionary and from that i am adding the content into some other dictionary

  //here contract is my json dictionary 
  NSArray *projectDBList =[contract allKeys];//listing all the keys in dict 

  NSMutableDictionary *projectsList=[[NSMutableDictionary alloc]init];

  [projectDBList enumerateObjectsUsingBlock:^(NSString * obj, NSUInteger idx, BOOL *stop) {

  [projectsList setObject:[contract objectForKey:obj] forKey:obj];

  }];

Sealer