Objective-C Language
NSDiccionario

Crear

NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];

o

NSArray *keys = [NSArray arrayWithObjects:@"key1", @"key2", nil];
NSArray *objects = [NSArray arrayWithObjects:@"value1", @"value2", nil];
NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects 
                                                       forKeys:keys];

o usando la sintaxis literal apropiada

NSDictionary *dict = @{@"key": @"value", @"nextKey": @"nextValue"};

NSDictionary to NSArray

NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];  
NSArray *copiedArray = myDictionary.copy; 

Obtener llaves:

NSArray *keys = [myDictionary allKeys];

Obtener valores:

NSArray *values = [myDictionary allValues];

NSDictionary a NSData

NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];  
NSData *myData = [NSKeyedArchiver archivedDataWithRootObject:myDictionary];

Ruta de reserva:

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

NSDictionary a JSON

NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];   

NSMutableDictionary *mutableDictionary = [myDictionary mutableCopy];
NSData *data = [NSJSONSerialization dataWithJSONObject:myDictionary options:NSJSONWritingPrettyPrinted error:nil];
NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

Enumeración basada en bloques

La enumeración de diccionarios le permite ejecutar un bloque de código en cada par de clave-valor del diccionario utilizando el método enumerateKeysAndObjectsUsingBlock:(void (^)(id key, id obj, BOOL *stop))block

Ejemplo:

NSDictionary stockSymbolsDictionary = @{
                                         @"AAPL": @"Apple",
                                         @"GOOGL": @"Alphabet",
                                         @"MSFT": @"Microsoft",
                                         @"AMZN": @"Amazon"
                                       };
NSLog(@"Printing contents of dictionary via enumeration");
[stockSymbolsDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
    NSLog(@"Key: %@, Value: %@", key, obj);
}];

Enumeración rápida

NSDictionary se puede enumerar utilizando la enumeración rápida, al igual que otros tipos de colección:

NSDictionary stockSymbolsDictionary = @{
                                     @"AAPL": @"Apple",
                                     @"GOOGL": @"Alphabet",
                                     @"MSFT": @"Microsoft",
                                     @"AMZN": @"Amazon"
                                   };

for (id key in stockSymbolsDictionary)
{
    id value = dictionary[key];
    NSLog(@"Key: %@, Value: %@", key, value);
}

Debido a que NSDictionary está intrínsecamente desordenado, el orden de las claves que en el ciclo for no está garantizado.