i have created NSMutableDictionary with 10 keys.Now i want to access NSMutableDictionary keys in a same order as it was added to NSMutableDictionary (using SetValue:* forKey:* );
How can i achieve that ?
Main Difference is:NSMutableDictionary is derived from NSDictionary, it has all the methods of NSDictionary. NSMutableDictionary is mutable( can be modified) but NSDictionary is immutable (can not be modified).
NSDictionary keys & values are not ordered.
You have to convert NSDictionary to NSMutableDictionary . You have to user NSMutableDictionary in place of the NSDictionary . After that you can able to change value in NSMutableDictionary . Save this answer.
An NSDictionary will retain it's objects, and copy it's keys. Here are some effects this has had on code I've worked on. Sometimes you get the same object you put in, sometimes not. Immutable objects are optimized to return themselves as a copy .
If you absolutely must use a dictionary container, you have to use a key that is sortable by the order in which you add key-value pairs. Thus, when creating your dictionary, you use a key that is an auto-incrementing integer or similar. You can then sort on the (integer) keys and retrieve the values associated with those keys.
If you do all of that, however, you may as well just use an NSMutableArray
and add values to the array directly! It will be much faster and require less code. You just retrieve objects in order:
for (id obj in myArray) { /* do stuff with obj... */ }
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