Playing with Array and Dictionary in Objective-C

playingWithDS.m

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {

        //Mutable Array
        NSMutableArray *array;
        array = [NSMutableArray arrayWithCapacity:4];
        [array addObject: @"one"];
        [array addObject: @"two"];
        [array addObject: @"three"];
                
        for(NSString *string in array){
            NSLog(@"%@", string);
        }
        
        //Dictionary
        NSDictionary *dict;
        dict = [NSDictionary dictionaryWithObjectsAndKeys: @"1", @"one", @"2", @"two", nil];
        
        NSLog(@"One: %@", [dict objectForKey: @"one"]);
        NSLog(@"Two: %@", [dict objectForKey: @"two"]);
        
        //Mutable Dictionary
        NSMutableDictionary *mDict;
        mDict = [NSMutableDictionary dictionary];
        [mDict setObject: @"1" forKey: @"one"];
        [mDict setObject: @"2" forKey: @"two"];
        
        NSLog(@"One: %@", [mDict objectForKey: @"one"]);
        NSLog(@"Two: %@", [mDict objectForKey: @"two"]);
        
        /*
         * Dictionaries can only hold objects and not primitive types. 
         * We can use primitive types as dict values by wrapping them into NSNumber
         */
        
        int number = 1;
        float floatval = 1.234566;
        char character = 'A';
        BOOL boolval = YES;
        
        NSNumber *intWrapper;
        intWrapper = [NSNumber numberWithInt: number];
        
        NSNumber *floatWrapper;
        floatWrapper = [NSNumber numberWithFloat: floatval];
        
        NSNumber *charWrapper;
        charWrapper = [NSNumber numberWithChar: character];   //Note: Don't use double quotes to wrap chars
        
        NSNumber *boolWrapper;
        boolWrapper = [NSNumber numberWithBool: boolval];
        
        NSMutableDictionary *varDict;
        varDict = [NSMutableDictionary dictionary];
        [varDict setObject: intWrapper forKey: @"integer"];
        [varDict setObject: floatWrapper forKey: @"float"];
        [varDict setObject: charWrapper forKey: @"char"];
        [varDict setObject: boolWrapper forKey: @"boolean"];
        //Store a  null value by wrapping it with NSNull
        [varDict setObject: [NSNull null] forKey: @"null"];

        NSLog(@"Integer: %@", [varDict objectForKey: @"integer"]);
        NSLog(@"Float: %@", [varDict objectForKey: @"float"]);
        NSLog(@"Char: %c", [[varDict objectForKey: @"char"] charValue]);
        NSLog(@"Boolean: %@", [varDict objectForKey: @"boolean"]);
        NSLog(@"NUll value: %@", [varDict objectForKey: @"null"]);
        
    }
    return 0;
}