I was using an NSMutableArray and realised that using a dictionary is a lot simpler for what I am trying to achieve.
I want to save a key as an NSString and a value as an int in the dictionary. firstly , how is this done? Secondly, what is the difference between mutable and a normal dictionary?
Regards.
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"];
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
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];
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!